World Book Blog

Rediscovering the Milky Way

2018-09-25T10:40:00-05:00

Earlier this year, in April, the European Space Agency (ESA) released the second trove of data gathered by the space probe Gaia (named after the ancient Greek goddess Gaia). Gaia’s precise measurements of the position, brightness, motion, and color of over 1.3 billion stars will transform astronomers’ understanding of our galaxy, the Milky Way.

The Milky Way contains the sun, Earth, and other objects in our solar system. It also includes hundreds of billions of stars besides the sun. Huge clouds of gas and dust lie throughout the galaxy, and they constantly form new stars. The Milky Way is so massive that about 10 smaller galaxies orbit it like satellites revolving around a planet.

Because our solar system is located within the Milky Way, vast clouds of dust and dense swaths of stars prevent astronomers from determining the galaxy’s exact structure. It is a bit like trying to see the outside of one’s home from the inside. Until now, astronomers had to guess what the Milky Way looks like by observing other galaxies with similar traits—the equivalent of looking at other houses from a window. Astronomers know the Milky Way is a spiral galaxy, with long arms extending out from a central core. But no one knows how many arms it has, what kinds of stars the arms contain, or whether the galaxy is a traditional spiral or a subtype called a barred spiral galaxy where the central core is elongated.

Gaia is like a flying drone taking photos around the neighborhood. Launched in 2013 by the ESA, Gaia traveled to a point behind Earth and began measuring the positions of over a billion stars. Gaia measures stellar distances using a technique called parallax. It first images a star against a background of other stars. Halfway around the sun, it takes another picture of the same star. Because the two pictures are taken from far distant positions, the star moves slightly in relation to its background. This is the same optical effect that makes an object at arm’s length to appear to change positions when viewed from just one eye or the other. Because scientists know how far away the two star pictures were taken, and how much the star appeared to move, they can precisely calculate its distance from Earth.

Gaia’s portrait of the Milky Way also extends into the fourth dimension—time. Over the course of its five-year mission, Gaia will map the sky 29 times. From those time-lapsed maps, astronomers can determine the speed and direction in which the galaxy’s stars and gas clouds are moving through space. This information tells us the origins of Milky Way objects and can even warn of galactic collisions or violent stellar explosions. This time-based study of the galaxy is called galactic archaeology.

Gaia is gathering more than just information about stars. The second data release also had the locations of 14,000 known asteroids within our solar system, allowing astronomers to precisely map their orbits. Future data releases will map even more solar system objects.

ESA released the first Gaia dataset in 2016. For each release, scientists have raced to mine the data for new discoveries. Usually, data from such spacecraft are temporarily reserved for scientists directly associated with the mission. But mission managers have released Gaia’s data to everyone at the same time. This has led to another impressive statistic: over 1,000 peer-reviewed scientific papers that use Gaia’s data have already been written since the first data release. Many thousands more will be written before all Gaia’s insights are revealed.

Image 1: In this artist’s impression, Gaia maps the stars of the Milky Way. Credit: ESA/ATG medialab/ESO/S. Brunier

Image 2: The space probe Gaia will tell us if the Milky Way is a traditional spiral galaxy, as in this illustration, or a barred spiral galaxy with an elongated central core. Credit: Artwork © Jon Lomberg and the National Air and Space Museum

Probing the Sun

2018-09-19T09:53:00-05:00

The sun is the center of our solar system and vital to life on Earth, but there is a lot we do not know about it. On August 12, the United States National Aeronautics and Space Administration (NASA) launched the Parker Solar Probe that will help unravel some of the the sun’s secrets. Over the next few years, the probe will orbit the sun at least 24 times and come blisteringly close to its surface. The probe will reach its first perihelion (the point of an orbit that is closest to the sun) on November 5.

The Parker Solar Probe is record setting in many ways. It will come within 3.8 million miles (6.1 million kilometers) of the sun, closer than any spacecraft in history. The current record-holder, NASA’s Helios 2, came within 27 million miles (43 million kilometers) of the sun in 1976. (Helios was the god of the sun in Greek mythology.) In comparison, Earth orbits about 93 million miles (150 million kilometers) from the sun, and Mercury, the planet nearest the sun, orbits about 36 million miles (58 million kilometers) away.

The Parker Solar Probe will also be the fastest object ever created by humans—another record it will take from Helios 2—traveling at some 430,000 miles (700,000 kilometers) per hour. Its high speed comes from the huge gravitational pull of the sun. As an object nears the sun, the sun’s gravity accelerates it, much in the way a drain accelerates a circling toy boat.

The probe is also the first to be named after a living person. In 1958, American scientist Eugene Parker hypothesized that ionized atoms were streaming from the sun. He coined the term solar wind for this phenomenon. This explained why a comet’s tail points away from the sun, no matter which direction it is traveling—something that had been observed for centuries but never fully understood. NASA named the groundbreaking probe after Parker to honor his contributions to heliophysics, the study of the sun and its effects on space.

Not far from the sun’s surface, the solar wind speeds up to more than 155 miles (250 kilometers) per second. Scientists are hoping to use the Parker Solar Probe to understand how and why this happens. The probe will dip into the sun’s corona (outer atmosphere) during its closest approaches. Temperatures there reach an unimaginable 4 million °F (2.2 million °C), far hotter than the temperature at the sun’s surface (10,000 °F, or 5,500 °C). Measurements made by the probe will help make sense of this temperature difference.

Getting close to the sun is not easy. The Parker Solar Probe launched from a Delta IV Heavy rocket, one of the most powerful rockets ever built. But it launched in the opposite direction of Earth’s orbit, causing it to slow down in relation to the sun and fall towards it. It will also use the gravity of Venus to slow it down further. At seven different times throughout its mission, it will pass close to Venus, which will act as a brake and hurtle the probe closer to the sun.

Operating close to the sun is also difficult. The Parker Solar Probe is protected by a thick, carbon-composite heat shield that faces the sun at all times. The sun interferes with radio signals at such close range, so the probe must operate without human contact for much of the time. Even getting power is difficult so close to the sun. Of course, solar energy is plentiful, but the scorching temperatures can fry solar cells. Parker’s panels will peek out from behind its heat shield only when the craft is at a safe distance, and they retract as the probe nears the sun.

Improving our knowledge of solar science may help prevent disasters on Earth. Solar events called coronal mass ejections (CME’s) come from the corona and can damage satellites and electrical systems on Earth. Findings from the Parker Solar Probe may help scientists better predict CME’s, allowing officials to temporarily shut down power grids to prevent major damage.

Image: In this NASA illustration, the Parker Solar Probe approaches the sun. The probe launched from Earth on Aug. 12, 2018, and will make its first close pass of the sun on November 5. Credit: NASA/Johns Hopkins APL/Steve Gribben

Chile’s Ancient Desert Calendar

2018-09-12T11:00:00-05:00

High in the Atacama Desert of Chile, a system of stone pillars and rock piles called saywas was recently found to be an ancient Inca calendar. Once thought only to mark a local Inca trail, a team of archaeologists, astronomers, historians, and researchers recently showed how the saywas work as a complicated and connected calendar to identify and predict equinoxes, solstices, and other astronomical events. The Inca trail in the Atacama Desert is part of the Qhapaq Ñan, an extensive Inca road network that stretches from southern Colombia to central Chile.

Working at 13,800 feet (4,200 meters) above sea level in the desert mountains near Taltal, a small city in northern Chile, the scientific team began visiting the saywas and taking measurements in 2017. The team included local indigenous people as well as experts from the Chilean Museum of Pre-Colombian Art, the nearby Atacama Large Millimeter/submillimeter Array (ALMA) observatory, and the European Southern Observatory. The research was funded by BHP/Minera Escondida, a mining company with more material interests in the desert.

The scientific team began the study by documenting alignments between certain saywas and the sunrises on the March equinox and June solstice. They then began connecting saywa points with other important dates on the ancient Inca calendar. Operating much in the same way as Stonehenge in England, the saywas align with sunrises on certain dates, while also projecting shadows on the ground that lead to other stone points. The researchers also found that certain saywas align with constellations at night, further strengthening the researchers’ conclusion, published in 2018, that the network of stones served as a large calendar for Inca astronomers.

The first written accounts of the saywas were recorded during the Spanish conquest of Andean South America in the 1500's and 1600's. The saywas’ remote locations in the empty desert, far from Inca cities, led the Spanish to believe that the stone piles were little more than pathway markers to help guide people through the vast, barren desert. The saywas did in fact aid in navigation, but the larger purpose of the stone markers remained unknown for centuries. In recent years, however, knowledge of the Inca has greatly expanded, and the study of ancient Quechua and Aymara (Inca languages) dictionaries led to the examination of the relationship between the saywas and the Inca astronomical system.

The ancient Inca capital of Cusco (in modern-day Peru) was surrounded by columns used to measure time, create calendars, and predict equinoxes and solstices as well as the planting and harvesting seasons. The remote saywas, however, were tucked away in the Atacama Desert. Perhaps that was merely the best view of the heavens, allowing Inca astronomers to get the most accurate measurements while Cusco was obscured by clouds and mist. Modern astronomers use the high desert for the same purpose. The sprawling ALMA observatory is only a (figurative) stone’s throw away.

Image: The sun peeks over the Andes Mountains at dawn, illuminating a line of ancient Inca saywas in the Atacama Desert of northern Chile. Credit: A. Silber, ALMA/ESO/NAOJ/NRAO

The Moons of Mighty Jupiter

2018-08-10T10:19:00-05:00

Astronomers at the Carnegie Institution for Science in Washington, D.C., recently discovered a new batch of moons orbiting Jupiter, the largest planet in our solar system. The new group of 12 moons—which bring’s Jupiter’s moon total to an astounding 79—includes an oddball, however: one is going “the wrong way.”

Led by astronomer Scott Sheppard, the Carnegie team had been looking for “Planet Nine,” a hypothetical major planet in the Kuiper belt, a band of objects in the outer regions of our solar system. In March 2017, Jupiter moved into the astronomers’ search area. The telescope the team was using was uniquely suited for finding small or faraway objects: it could block out light from larger nearby heavenly bodies. Sheppard took time away from Planet Nine to poke around Jupiter, and his curiosity was rewarded with the discovery of 12 new moons. The first two bodies orbit close to Jupiter, and were quickly confirmed as moons. The other 10 skew farther out from the mighty planet and were not announced as moons until July 17, 2018.

The new moons are small, some less than a mile (several hundred meters) in diameter. Their orbital characteristics tell scientists a lot about them. Nine of the 10 newest moons orbit in retrograde, meaning in the opposite direction of the rotation of Jupiter. This leads the astronomers to think they formed from objects captured by Jupiter’s hefty gravitational pull. Most moons form with their parent planet and have prograde orbits, meaning they orbit in the same direction as the host planet. But captured objects often have retrograde orbits. Sheppard’s team thinks these nine moons are parts of captured objects broken up by collisions over millions or billions of years.

The tenth of the newest moons, however—which Sheppard calls Valetudo, a great-granddaughter of the Roman mythological god Jupiter—travels in a prograde orbit. It dives through the orbits of the other nine moons, putting it on an eventual collision course. When moon finally meets moon, the impact will either destroy the bodies or make them even smaller.

Image 1: Ganymede is the largest of Jupiter’s moons. Astronomers recently found 12 new and much smaller moons orbiting Jupiter, bringing the planet’s solar system-leading total to 79. Credit: NASA

Image 2: Callisto, another large moon of Jupiter, has a diameter of almost 3,000 miles (4,800 kilometers), many times the size of Jupter’s newly discovered moons. Credit: NASA

Mars is InSight

2018-06-07T09:29:00-05:00

Last month, on May 5, the United States National Aeronautics and Space Administration (NASA) launched a new Mars probe called Insight from Vandenberg Air Force Base in California. InSight is short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport. InSight, a probe that will study the formation of Mars, is NASA’s first interplanetary mission launched from the west coast of the United States. All previous such launches took place at Cape Canaveral Air Force Station in Florida.

The InSight mission cost just $814 million, a relatively small sum in the multibillion-dollar science of space exploration. The bargain probe will break new ground, however, quite literally, by drilling into the Martian surface. It will sample temperatures, measure the magnetic field, and record seismic levels, all to help scientists understand the planet’s formation. The data may also shed light on the formation of Earth and our solar system.

Earth has three major layers: the crust, the mantle, and the core. Planetary scientists think our solar system’s other rocky planets—Mercury, Venus, and Mars—also have these layers. Scientists are unsure, however, how thick the layers are in the other planets. Earth has churned itself up through the process of plate tectonics, changing the chemical makeup and size of its layers over time. But Mars, the fourth planet from the sun, has experienced much less seismic activity. The planet’s present structure, then, should somewhat resemble its original composition when the solar system was formed.

InSight carries three instruments vital to its mission. The Seismic Experiment Interior Structure (SEIS) sensor will study seismic waves from marsquakes (the Martian equivalent of earthquakes) to determine the structure of the interior of Mars. The Heat Flow and Physical Properties Package (HP³) will drill down almost 15 feet (5 meters) below the Martian surface—the deepest extraterrestrial excavation to date. As it drills, HP³ will record temperature changes to see how much heat remains from Mars’s formation billions of years ago. Scientists can determine the age of rocks, fossils, and other objects by measuring the radioactive elements in them, a science called radiogeology. A third InSight instrument will measure Mars’s magnetic field.

In an unusual arrangement, a robotic arm will move SEIS and HP³ from docks on the body of the lander to the surface of Mars. Tethers will control and power the instruments. Other than that, InSight’s design is pretty standard. Engineers reused much of the design of NASA’s Pheonix lander, which, in 2008, studied the history of water on Mars. By reusing this successful design, engineers saved many millions of dollars on the mission.

Two CubeSats (miniature satellites) hitched a ride on InSight’s rocket and are also traveling to Mars. The CubeSats are the first such satellites to venture beyond Earth’s orbit, and they will help transfer data from InSight during the probe’s landing.

InSight is scheduled to land on Mars on Nov. 26, 2018. Despite NASA’s strong recent record for Mars missions and the use of the proven Phoenix platform, success is far from guaranteed. Over the years, nearly two-thirds of all Mars missions have failed before completing their planned observations.

Image 1: This artist’s rendition shows the InSight lander operating on the surface of Mars. The probe is scheduled to land on Mars on Nov. 26, 2018. Credit: NASA/JPL-Caltech

Image 2: A NASA Atlas V rocket carrying InSight breaks through the clouds above Vandenberg Air Force Base in California on May 5, 2018. Credit: Cory Huston, NASA

Image 3: Beginning in late November 2018, NASA’s InSight probe will study the formation of Mars, the fourth planet from the sun. Credit: NASA/JPL/Malin Space Science Systems

NASA’s New Planet Hunter

2018-04-24T09:14:00-05:00

Last week, on April 18, a next-generation planet-hunting satellite was carried into orbit. The Transiting Exoplanet Survey Satellite (TESS) was launched from Cape Canaveral in Florida. Designed by the United States National Aeronautics and Space Administration (NASA), TESS will search for exoplanets (planets orbiting stars beyond our solar system).

TESS was carried into space by a SpaceX Falcon 9 rocket. After boosting the satellite into orbit, the first stage of the rocket landed on a crewless barge in the Atlantic Ocean and will be used again. When TESS reaches its desired orbit, it will undergo testing and calibration before it begins the search for exoplanets.

TESS will replace NASA’s planet-hunting satellite Kepler, which is almost out of fuel. Launched in 2009, Kepler has discovered thousands of exoplanets. Like Kepler, TESS will use the transit method to search for exoplanets. As an exoplanet passes in front of its parent star, it blocks out a tiny portion of the star’s light (an event called a transit). TESS can detect these telltale dips in the intensity of the light.

Although TESS will use the transit method, it is far from a Kepler clone. TESS will study brighter stars than Kepler did. This means that all of TESS’s targets will be at most 200 light-years from Earth. Because TESS is limited to closer, brighter stars, it will be easier for astronomers to confirm the finds and perform follow-up studies. TESS will also be able to observe the whole sky, as opposed to Kepler’s ability to only study small sections of sky at a time. TESS will also focus its search on finding Earth-sized exoplanets, especially those that orbit their star in the habitable zone, the range of an orbit where liquid water may be present on a planet’s surface. Liquid water is necessary for all life on Earth.

One of the tools astronomers will use to follow up on TESS’s discoveries will be NASA’s James Webb Space Telescope (JWST). The JWST is the most powerful space telescope ever built. Due to launch in 2020, it will be able to search for possible signs of life on the planets that TESS finds. Another observatory will be the Characterizing Exoplanets Satellite (CHEOPS). Designed by the European Space Agency, CHEOPS will launch at the end of 2018. Rather than being strictly a planet hunter, CHEOPS will focus on studying the makeup of smaller exoplanets that have already been discovered. It will likely be able to better define some of the exoplanets TESS discovers.

Astronomers have long hoped to learn whether—and, if so, where—other life exists in the universe. With TESS, JWST, and CHEOPS, they will be able to pinpoint nearby exoplanets with potential for life. But it will likely take even more advanced telescopes to determine if the planets actually teem with living things, like Earth.

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Image 1: At Cape Canaveral Air Force Station in Florida, the SpaceX Falcon 9 rocket carrying NASA’s Transiting Exoplanet Survey Satellite (TESS) lifts off on April 18, 2018. Credit: SpaceX

Image 2: NASA’s Transiting Exoplanet Survey Satellite (TESS), shown here in a conceptual illustration, will identify exoplanets orbiting stars beyond our solar system. Credit: NASA Goddard Space Flight Center

The End of Tiangong-1

2018-04-11T09:28:00-05:00

Last week, on April 1, China’s first space station, Tiangong-1, returned to its home planet in a fiery “uncontrolled return” through Earth’s atmosphere. Tiangong-1 (Heavenly Palace-1 in English) was launched in 2011 and ceased operating in 2016. The remnants of the unoccupied space station—the parts that did not disintegrate on reentry—crashed into the South Pacific Ocean.

The spacecraft’s demise was tracked closely by the United States National Aeronautics and Space Administration (NASA), the U.S. Air Force, and other space agencies and air forces around the world. The end of Tiangong-1 could have posed a threat to highly populated areas, and the derelict craft’s reentry position was continually updated as it spun through its final orbits. At last, Tiangong-1 hit the atmosphere over a wide expanse of empty sea. Most of the spacecraft was incinerated, but pieces of it did strike the water at Earth’s surface.

Tiangong-1 was launched aboard a carrier rocket from the Jiuquan Space Launch Center in northern China in September 2011. The modest space station, two cylindrical sections with a docking port, was about 39 feet (12 meters) long and 11 feet (3.3 meters) wide. The spacecraft was used mainly to carry out rendezvous and docking tests in preparation for the construction of a larger and longer-lasting space station scheduled for completion and launch in the early 2020's. Tiangong-1 settled into an orbit about 217 miles (350 kilometers) above Earth, slightly lower than the orbit of the much larger International Space Station.

In early November 2011, the robotic Shenzhou-8 (Divine Craft-8) spacecraft visited Tiangong-1, executing China’s first-ever orbital docking. In June 2012, three taikonauts (Chinese astronauts) aboard Shenzhou-9 gave the heavenly palace life for about two weeks. A year later, three more taikonauts spent a fortnight aboard Tiangong-1. The spacecraft continued some Earth-observation work after that, but contact and control of Tiangong-1 were lost in March 2016. A successor craft, Tiangong-2, was launched in September 2016 and is currently in operation.

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Image: This illustration shows the uncontrolled return of the Tiangong-1 space station on April 1, 2018. Credit: © Alejo Miranda, Shutterstock

Colliding Neutron Stars

2017-10-27T10:23:00-05:00

On August 17, a faint chirp from instruments at the Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States set off a mad scramble in observatories around the world to catch a glimpse of something never before observed: the cosmic collision of two neutron stars (an event called a kilonova). In the extraordinary events that followed, the signal initially detected by LIGO was picked up by as many as 70 Earth and space-based telescopes, providing a remarkably detailed picture of one of the most violent, cataclysmic events in the universe. The significant observation was announced by LIGO scientists on October 16.

LIGO is a pair of facilities built to detect gravitational waves, types of radiation created by the movement of matter through space. LIGO consists of three detectors—two near Richland, Washington, and one in Livingston, Louisiana. The LIGO detectors are designed to find gravitational waves created by such violent cosmic events as collisions between black holes, objects with gravitational forces so strong that nothing can escape them. The first gravitational waves were detected by LIGO on Sept. 14, 2015. The waves were generated by colliding black holes billions of light-years away from Earth.

The recent kilonova observation was significant for several reasons. It was the first time LIGO had detected the weaker gravitational wave generated by a collision between neutron stars, the smallest and densest types of known stars. The kilonova signal was also detected at the European Gravitational Observatory (EGO) interferometer, called Virgo, located near Pisa, Italy. With data from multiple observatories, astronomers were able to determine the starting point of the gravitational wave. As word of the signal spread, dozens of other telescopes on Earth and in space were trained on the location to detect other kinds of energy from the cosmic collision. Astronomers were able to observe the resulting fireball in visible light from telescopes. Other telescopes recorded the gamma rays, radio waves, ultraviolet rays, and X rays generated from the collision. It was the first time such a cosmic event had been seen by astronomers, witnessed in wavelengths across the electromagnetic spectrum.

The gravitational wave signal detected by LIGO came from two neutron stars orbiting each other about 130 million light-years away. Each neutron star had slightly more mass than our own sun, but all that mass was crammed into a sphere only about 20 miles (32 kilometers) in diameter. The doomed stars circled each other 30 times a second as they neared to within about 200 miles (320 kilometers) of each other. The orbit increased to about 2,000 times per second just before they collided in an impact that released a tremendous burst of energy. What happened next is uncertain. Scientists think that after the stars collided they may have formed a heavier neutron star or collapsed into a black hole.

Some telescopes were able to spot a faint flash in the night sky. That flash was generated in the fireball of the collision as radioactive heavy chemical elements were blown away at nearly one-fifth the speed of light. Scientists had long theorized that such catastrophic celestial collisions were necessary to forge heavy chemical elements, such as gold, platinum, and uranium. The spectrum of light coming from the observed collision of neutron stars helped confirm this theory. They calculated that the explosion created about 100 times the mass of Earth in gold. Scientists now believe such collisions of neutron stars are common in the universe. They believe that most heavy element atoms in the universe are formed in such kilonova events.

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Image: This artist’s representation shows two neutron stars colliding, a cataclysmic event known as a kilonova. Astronomers witnessed a kilonova for the first time on Aug. 17, 2017. Credit: © Robin Dienel, Carnegie Institution for Science

TC4: Earth’s Close Shave

2017-10-13T09:16:00-05:00

Yesterday, on Thursday, October 12, a house-sized asteroid buzzed Earth, passing within the orbit of the moon and uncomfortably close to hundreds of orbiting communications and weather satellites. Officials at the United States National Aeronautics and Space Administration (NASA) insisted there was never any danger of a collision. They first discovered the space rock, called 2012 TC4, five years ago and have been following it ever since. The close shave by TC4 posed no threat, but it did provide NASA with an opportunity to test systems that detect orbiting objects and to develop plans to respond to a potentially catastrophic impact.

Technicians from NASA and the European Space Agency’s Near-Earth Object program measured TC4 to be about 50 to 100 feet (15 to 30 meters) in diameter. It is traveling through space at about 16,000 miles (25,800 kilometers) per hour. At its closest, it will pass by southern Australia a mere 27,300 miles (44,000 kilometers) above the surface, just beyond the 22,400-mile (36,000-kilometer) plane of Earth’s most remote geosynchronous (fixed-orbit) satellites.

Technicians at the space agencies determined that TC4 makes an elongated orbit around the sun every 609 days. They calculate that TC4 will pass close to Earth again in 2050 and 2079. For now, the calculations show that there is no danger of TC4 striking Earth. However, should TC4’s orbit be deflected by even a small amount, the chances of an impact could increase. Officials say there is a 1-in-750 chance that TC4 could strike Earth sometime after 2050. Those are long odds, to be sure, but NASA scientists continue to track TC4 nonetheless, as well as 12 other asteroids with a greater risk of impact.

Scientists know that Earth has been struck by asteroids and meteors repeatedly over the past 4.5 billion years. NASA experts estimate that objects the size of TC4 fly past Earth about three times per year. They point out, however, that the chances of a serious asteroid impact anytime soon are remote. But even the experts are occasionally taken by surprise. The Chelyabinsk meteor, a chunk of rock similar in size to TC4, fell into Earth’s atmosphere and exploded over the city of Chelyabinsk in southeastern Russia on Feb. 15, 2013. The impact frightened thousands of people and took NASA and other space-observing agencies by surprise. They did not see that one coming.

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Image 1: This illustration depicts the safe flyby of asteroid 2012 TC4 as it passes by Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Image 2: This illustration shows the path of asteroid 2012 TC4 as it passes within the moon’s orbit of Earth on Oct. 12, 2017. Credit: NASA/JPL-Caltech

Mythic Monday: Winged Pegasus

2017-09-25T09:47:00-05:00

Look, up in the sky! It’s a bird! It’s a plane! It’s Superhorse! If you have ever stargazed in the Northern Hemisphere, you might have noticed Pegasus, a constellation resembling part of a horse. As commonly drawn, the constellation—named for Pegasus, the immortal winged horse of Greek mythology—appears to be galloping upside down across the heavens. Pegasus was among dozens of constellations cataloged by the ancient Greek mathematician Ptolemy about A.D. 150 in his great work Mathematike Syntaxis. Here on Earth, Pegasus the flying horse is one of the more interesting figures of mythological lore.

The Pegasus of mythology was the offspring of the Gorgon Medusa, a monstrous woman with snakes for hair, and Poseidon, the Greek god of the sea and earthquakes—and horses. The Gorgons were three sisters in Greek mythology whose ugliness could turn a viewer to stone. Pegasus was born when Perseus, a hero in Greek mythology, slew the pregnant Medusa by cutting off her head. Pegasus sprang fully grown from Medusa’s head—or from her neck or her blood or the soil fertilized by her blood, depending on the account. Pegasus was born along with a brother, Chrysaor, sometimes described as a giant and bearing a golden sword. Pegasus had a half-brother, Arion, who also was a magical horse and a son of Poseidon.

The Greek legendary hero Bellerophon tamed Pegasus with help from the goddess Athena. One story tells that a prophet advised Bellerophon to sleep on Athena’s altar. There, Bellerophon dreamed that Athena gave him a golden bridle and ordered him to make a sacrifice to Poseidon. When he awoke, Bellerophon found a bridle on the altar. He sacrificed a bull to Poseidon and discovered Pegasus at a spring, waiting to be bridled.

Bellerophon and Pegasus had many adventures together. In one, the Lycian King Iobates sent Bellerophon to kill the Chimera, a fire-breathing monster that was part lion, part goat, and part serpent. Pegasus and Bellerophon flew over the Chimera, and Bellerophon slaughtered the monster with arrows. Pegasus also helped Bellerophon defeat the Amazons, a tribe of warrior women, and another tribe called the Solymoi. Bellerophon, a mortal human being, later tried to ride Pegasus up Mount Olympus, the home of the gods. Zeus, the ruler of the gods, became angry and sent a gadfly to sting Pegasus. The horse bucked, throwing Bellerophon down to Earth and crippling him. Pegasus then lived on Olympus, where he served Zeus by carrying the god’s thunderbolts.

Pegasus’s name may have come from the Greek word pêgê, meaning spring, and it is said that he created springs by striking the ground with a hoof. One of these springs, the Hippocrene spring on Mount Helicon, is associated with poetic inspiration. Some sources say that Zeus eventually turned Pegasus into the constellation that bears his name. If you would like to see the celestial superhorse for yourself, the constellation is best viewed in the northern sky from September through November.

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Image 1: Statue of Pegasus. Credit: © Shutterstock

Image 2: Mercury (a.k.a Hermes) rides Pegasus in the Jardin des Tuilieries Paris, France. Credit: © Zoran Karapancev, Shutterstock

The September Equinox

2017-09-22T09:38:00-05:00

Today, at 4:02 p.m. Eastern Time, the autumnal equinox marks the beginning of autumn in the Northern Hemisphere. In the Southern Hemisphere, where the seasons are reversed, the event is called the vernal equinox and marks the start of spring. The word vernal means of spring. An equinox is either of the two moments each year (the other is in March, again changing the seasons) when the sun is directly above Earth’s equator. On the days of the equinoxes, all places on Earth receive approximately 12 hours of sunlight. Today, the sun rose at 6:43 a.m. Eastern Time and will set at 6:52 p.m.—a total of 12 hours and 9 minutes of daylight. The term equinox comes from a Latin word meaning equal night. The equinoxes occur at different times of day each year on March 19, 20, or 21 and on September 22 or 23.

The time interval from the March equinox to the September equinox is longer than that between the September equinox and the next March equinox. This time difference results from the Earth’s elliptical (oval-shaped) orbit around the sun. Our planet moves faster in its orbit when it is closer to the sun. The distance between the Earth and the sun is shortest in January. Therefore, the Earth completes the semicircle from the September equinox to the March equinox faster than it does the opposite semicircle.

Astronomers also use the term equinox for either of two imaginary points where the sun’s apparent path among the stars crosses the celestial equator. The celestial equator is an imaginary line through the sky directly over the equator.

After the autumnal equinox, the weather cools and nights become longer than days, and days continue to shorten until the winter solstice. The weather then warms and daylight begins its recovery toward the summer solstice in June. The winter solstice is technically the shortest day of the year, and the day of the summer solstice enjoys the most sunlight.

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Image: The equinoxes are the two moments of the year when the sun is directly above the equator. As Earth moves in its orbit around the sun, the position of the sun changes in relation to the equator, as shown by the dotted lines in this diagram. The sun appears north of the equator between the March equinox and the September equinox. It is south of the equator between the September equinox and the next March equinox. Credit: WORLD BOOK diagram

Cassini’s Grand Finale

2017-09-19T10:55:00-05:00

Cassini is gone. For more than 13 years, the space probe revealed the secrets of Saturn. It ended its mission in a blaze of glory on Friday, September 15, crashing into the planet it had studied for so long.

Cassini was a spacecraft sent to Saturn to study the planet and its rings and satellites. The United States National Aeronautics and Space Administration (NASA) launched Cassini on Oct. 15, 1997. The craft began orbiting Saturn on July 1, 2004. Engineers and scientists at NASA’s Jet Propulsion Laboratory built Cassini. The Italian Space Agency provided a large antenna and several other elements of the spacecraft. The craft was named for the Italian-born French astronomer Giovanni Domenico Cassini, who made major discoveries about Saturn in the late 1600’s.

Cassini regularly provided spectacular revelations about the Saturn system. It discovered lakes of liquid hydrocarbons on Saturn’s moon Titan, the first lakes observed outside of Earth. The probe also discovered vertical structures in Saturn’s rings, structures rising high above the equatorial plane.

Perhaps its most important discovery, however, was the detection of favorable conditions for life within the icy moon Enceladus. Measurements from Cassini revealed that a global ocean of liquid water lies beneath Enceladus’s icy crust. Furthermore, the probe imaged—and even flew through—plumes of ice crystals created by geysers at the moon’s surface. Cassini determined that these geysers were powered by hydrothermal activity in the ocean floor and that the plume contained hydrocarbon compounds. With these discoveries, Enceladus leapt to the top of the list of other places in the solar system where life might have developed.

Nearing 20 years in space, Cassini was running low on fuel. Mission planners directed Cassini to hurtle into Saturn’s clouds. Scientists were concerned that if the probe ran out of propellant and orbited uncontrollably within the Saturn system, it could have crashed into Titan or Enceladus. If this had occurred, any microbes from Earth surviving on Cassini’s surface could have contaminated these moons. Cassini sent back data and images right up to its final plunge into Saturn’s atmosphere.

Saturn will be without a visiting spacecraft from Earth for some time. With NASA trying to develop both the James Webb Space Telescope and the Space Launch System within its tight budget, planetary exploration has fallen by the wayside. Such probes take at least 5 to 10 years to plan and build. Then, it would take another six years or so for a spacecraft to reach Saturn. Therefore, any follow-up probe to Saturn would be at least a dozen years in the future.

Cassini may be gone, but its impact on the study of Saturn will continue to be felt for many years. Over 3,000 scientific papers have already been published based on data gathered by Cassini, and more are on the way. Current and future scientists will be using data gathered by Cassini to make new discoveries about the ringed planet for decades to come.

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Image 1: Cassini photographed Saturn illuminated from behind by the sun. This panoramic view was created by combining 165 images taken by Cassini’s wide-angle camera over nearly three hours on Sept. 15, 2006. Credit: NASA/JPL/Space Science Institute

Image 2: This artist’s conception shows Cassini diving between Saturn and the planet’s innermost ring. Credit: NASA/JPL-Caltech

Image 3: This photograph of Saturn’s northern hemisphere was among the last taken by NASA’s Cassini spacecraft on Sept. 13, 2017. Credit: NASA/JPL-Caltech/Space Science Institut

Moon, Sun, Eclipse

2017-08-22T10:49:00-05:00

This photograph, taken from Northern Cascades National Park in Washington, shows the moon passing before the sun during the solar eclipse of Aug. 21, 2017. Credit: Bill Ingalls, NASA

Yesterday, on August 21, huge crowds gathered across the United Statesto watch the solar eclipse within the path of totality, the 70-mile (113-kilometer) wide swath of land from Oregon to South Carolina where the moon completely covered the sun. In Newport, Oregon, throngs of sky watchers greeted the eclipse as it made first landfall at 10:15 a.m. local time. Many thousands of eclipse chasers filled the totality town of Carbondale, Illinois (where the eclipse was longest). Local merchants greeted the tourists with special jewelry, cookies, doughnuts, and other eclipse-themed goods. Across the country, roads toward the path of totality were jammed with traffic and hotels were booked solid—sometimes a year or more in advance of the big event.

A total solar eclipse can have a powerful psychological effect on people. Many people, especially in large urban areas, don’t often have reason to look toward the sky in the middle of the day. But, as the moon begins to move over the sun, people could not help but notice the odd darkening of the sky unlike anything they had ever seen. Many people reported feeling a profound sense of awe and a spiritual connection with other people. Others reported a tremendous feeling of unease as the sunlight dimmed and gradually faded completely. But, unlike the experience in ancient times, there were no reports of panic among the masses of eclipse watchers. Astronomers have long been able to precisely predict the time and place of such celestial events. Yesterday, people cheered and applauded the eclipse as they might ooh and aah at a fireworks show, and eclipse glasses (with lenses dark enough to safely view the sun) were passed from hand to hand.

The moon totally blocks the sun during the solar eclipse of Aug. 21, 2017, above Madras, Oregon. Only the sun’s corona is visible around the moon. Credit: Aubrey Gemignani, NASA

At peak totality, the bright disk of the sun was replaced by a dark spot, surrounded by a blazing ring–the sun’s outer atmosphere (called the corona) that is easily visible only during an eclipse. In some regions, people felt a noticeable temperature drop as day briefly turned to night. Stars and planets became visible in the midday sky. Crickets began chirping, thinking night had begun a bit early, and birds roosted and went silent. Some eclipse chasers were surprised and annoyed by mosquitoes, which were fooled into thinking dusk had arrived and went hunting a few hours early.

People gaze skyward wearing eclipse glasses during the solar eclipse of Aug. 21, 2017, on the Oregon State University campus in Corvallis, Oregon. Credit: Mark Floyd, Oregon State University (licensed under CC BY-SA 2.0)

The great solar eclipse of 2017 left the United States just north of Charlotte, South Carolina, at 4:10 p.m. local time. Peak totality ended at 2:49 p.m. at that location. Anyone who missed the eclipse this year will not have to wait long for another chance. The next total solar eclipse visible from a large portion of the United States will occur on April 8, 2024. And Carbondale, Illinois, will once more have a chance to shine. It is the only city that will be in the path of totality in both 2017 and 2024. It’s not too early to start planning!

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Coming Attraction: A Total Eclipse

2017-08-18T11:25:00-05:00

Get ready! On Monday, August 21, if you live in the United States from Oregon to South Carolina, you will be able to experience one of nature’s most impressive sights–a total eclipse of the sun. Across the United States, large crowds are expected in towns, cities, and campsites along the path of totality for the spectacular celestial show. The path of totality is the narrow swath, about 70 miles (110 kilometers) wide, along which the moon will completely blot out the sun.

A total solar eclipse occurs when the Earth, sun, and moon are in nearly a straight line and the moon’s shadow sweeps across the face of Earth. The dark moon appears on the edge of the sun and moves slowly across. At the moment of totality, a brilliant halo flashes into view around the darkened sun. This halo is the sun’s outer atmosphere, the corona. The sky remains blue but darkens dramatically. Some bright stars and planets will become visible and the temperature will noticeably drop. After a few minutes, the sun reappears as the moon continues on its orbit. The period when the sun is totally darkened may be as long as 7 minutes 40 seconds, but it averages about 2 1/2 minutes.

A total eclipse of the sun, as shown here, starts at the left. The moon gradually covers the sun, shown photographed through a filter. At the time of the total eclipse, photographed without a filter, the sun’s corona (outer atmosphere) flashes into view. The sun reappears as the moon moves on. Credit: © Atlas Photo Bank/ Photo Researchers

In the United States, the path of totality will cross 14 states: Oregon, Idaho, Wyoming, Montana, Nebraska, Iowa, Kansas, Missouri, Illinois, Kentucky, Tennessee, Georgia, North Carolina, and South Carolina. This will be the first total solar eclipse to cross the United States from coast-to-coast since June 8, 1918, when a total solar eclipse darkened skies from Washington to Florida. The last total solar eclipse to be seen anywhere in the continental United States was in 1979.

Makanda, a village in southern Illinois just south of Carbondale, will see the longest duration of totality for the eclipse–about 2 minutes and 40 seconds. If you miss out, though, don’t worry. Another total solar eclipse will cross the same area in 2024!

If you are going to view the eclipse, be careful! Looking directly at the sun, even during an eclipse, can severely damage your eyes, even if you are wearing sunglasses. If you wish to look directly at the eclipse you will need “eclipse glasses” which have special solar filters. Make sure that your eclipse glasses are undamaged and meet safety standards. Be careful to look away from the sun when you put your eclipse glasses on and take them off. A total solar eclipse can be viewed safely without protection in the path of totality only during the brief time when the disk of the sun is completely hidden.

Hot Water in Icy Space

2017-05-17T11:56:00-05:00

Enceladus, a moon of Saturn, contains geysers at its south polar region that spray water vapor and grains of water ice into space. Credit: NASA/JPL/Space Science Institute

Enceladus, an icy moon orbiting Saturn, is quickly becoming one of the hottest spots in the search for life beyond Earth. A group of scientists led by J. Hunter Waite of the Southwestern Research Institute in San Antonio, Texas, has determined that hydrothermal vents (flows of heated water) likely exist in a global ocean beneath Enceladus’s icy crust. These vents could possibly be home to life forms. Waite and his team published their findings last month in the journal Science.

Enceladus is the sixth largest moon of Saturn. Its surface, made of bright ice, makes it the most reflective object in the solar system. Like only a few known satellites, Enceladus shows signs of ongoing geological activity. Scientists have observed a plume of particles erupting from Enceladus’s south polar region. The plume is fed by several individual jets on the surface of the moon that release mostly water vapor and grains of water ice. These jets are in turn fed by a global ocean of liquid water that exists deep beneath the moon’s surface. The jets spray material onto Enceladus’s surface and into space.

The icy surface of Enceladus, seen here in a Cassini probe image, is continually smoothed by active geysers and shows few craters. Credit: NASA/JPL/Space Science Institute

Much of what is known about the moon comes from data gathered by the Cassini spacecraft launched by the United States National Aeronautics and Space Administration (NASA) in 1997. Cassini first visited Enceladus in 2005. The ship sampled Enceladus’s geysers in 2008 and again in 2015. It detected Enceladus’s global subsurface ocean in 2015.

This artist’s conception shows Cassini nearing the rings of Saturn. Credit: NASA/JPL

Waite and his coauthors analyzed the data obtained by Cassini and found molecular hydrogen (H₂) in Enceladus’s plumes. Such hydrogen is thought to be rare in planetary bodies as small as Enceladus, which has a circumference of roughly 1,000 miles (1,600 kilometers), making it less than 1/6th the size of Earth’s moon. Waite and his team determined that the hydrogen most likely came from hydrothermal vents on a sea floor within Enceladus. On Earth, hydrothermal vents are places where heated water flows from the ocean floor. Some deep-sea vents support diverse and exotic communities of marine life. Certain microbes can use the heat of the water to produce energy. These microbes are in turn consumed or harbored by larger organisms. Scientists suspect that life could flourish around such vents on other planets or moons.

Cassini has revealed tantalizing details about Enceladus, but it will not be able to determine if life exists beneath the moon’s icy surface. Cassini’s mission is coming to an end because the craft is running out of fuel. Cassini is now making a series of orbits between Saturn and its nearest ring. In September, when Cassini completes these orbits, it will crash into Saturn. Even if Cassini could continue its mission, it would be unable to gather more detailed information on the moon’s water jets. When the probe was launched 20 years ago, astronomers had not yet observed Enceladus’s polar plumes, so they could not have included instruments to study it specifically. Energized by these new findings, engineers are now working to design a probe that can sample Enceladus’s jets in greater detail. Such a probe would carry instruments designed to look for and study organic (carbon-containing) molecules in the plumes to determine if the molecules came from living things.

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Mythic Monday: Martial Mars

2017-05-15T11:17:00-05:00

Mars, the Roman god of war, was known as Ares in Greek mythology. Credit: © INTERFOTO/Alamy Images

This week’s mythology star, Mars, the god of war, held a special place in the hearts of the ancient Romans—not because of the god’s warlike nature but because the Romans considered him the father of the legendary founders of Rome, Romulus and Remus.

The Romans did not always think of Mars as a war god. Originally, they worshiped him as the god of farmland and fertility. They named the first month of their crop-growing season after him. Known by the Romans as Martius (our March), that month was also the beginning of the Roman year.

After they came into contact with the Greeks, the Romans gave Mars the characteristics of the Greek god of war, Ares. Over time, Mars became associated principally with war and conquest. The Romans offered sacrifices to Mars before and after battles.

However, one of the most famous stories about Mars does not involve war at all—or at least not armies in conflict. The tale concerns the god’s affair with Venus, the goddess of love. Possessed of a dazzling beauty, Venus was married to Vulcan, who was considered the least attractive of the gods. Vulcan was the blacksmith to the gods as well as the god of fire, metalworking, and skilled craftwork in general.

According to one version of the story, the sun witnessed a secret romantic meeting of Mars and Venus. Shocked by the affair, the sun told Vulcan about it. Vulcan immediately prepared a trap for the lovers. He crafted a huge net made of a metal that was incredibly strong but so fine that it could not be seen. Vulcan took the net and arranged it around the bed in his and Venus’s bedchamber. Before long, Venus and Mars met for another romantic tryst. As they embraced, the net closed on them, and they were trapped—caught in the midst of their affair. Then Vulcan, hoping to shame the lovers, showed other gods into the bedroom to see the lovers snared in the net. However, the gods did not cry “shame” or berate the lovers as he hoped they would. Instead, the gods laughed and laughed at the sight, and delightedly told the story again and again. Through the years, besides being a popular tale among the Roman gods, the story of the love affair between Venus and Mars became a favorite subject for poets and painters here on Earth.

In some ways, Mars lives on. In addition to having the third month of our calendar named after him, his is the name given to the fourth planet of our solar system. The planet Mars can be seen with the unaided eye and was known to ancient observers. As they gazed upon the blood-red planet, the Romans associated it with war and conflict and so they named it after Mars, their god of war.

And by the way, the next time you hear a march or the martial music of a military band, maybe give a thought to Mars. After all, the words march and martial are both based on his name.

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Record U.S. Space Time

2017-05-10T09:06:00-05:00

In April 2017, U.S. astronaut Peggy Whitson set an American record with her 535th day in space. Credit: NASA

Last month, on April 24, United States National Aeronautics and Space Administration (NASA) astronaut Peggy Whitson set a new record for cumulative time in space by an American astronaut as she began her 535^th day beyond Earth’s atmosphere. Currently on board the International Space Station (ISS), Whitson surpassed the previous record of 534 total space days set by astronaut Jeffrey Williams in 2016.

An astronaut is a person who pilots a spacecraft or works in space, particularly in the space program of the United States. In Russia and the other former republics of the Soviet Union, such men and women are called cosmonauts. Astronauts and cosmonauts operate spacecraft and space stations, launch and recapture artificial satellites, and conduct scientific experiments.

Peggy Whitson began her career at NASA in 1989, and she was selected to be an astronaut in 1996. In 2002, she spent six months aboard the ISS, performing several spacewalks to help assemble the station. During this time, NASA appointed her as the station’s science officer. She was the first person to serve in this position. In 2007, she embarked on another six-month mission to the ISS. Whitson served as the station’s first female commander, overseeing its further expansion. She began another tour at the station in November 2016, again serving as commander.

In addition to her new time-in-space record, Whitson has spent more than 53 hours on spacewalks outside the ISS. Whitson celebrated her 57^thbirthday on board the ISS in February 2017, making her the oldest American woman to spend time in space. By the time she returns to Earth in September, she will have logged 666 days in orbit over the course of three missions. The world record for the number of days in space is held by Russian cosmonaut Gennady Padalka, who logged 879 days in orbit over several missions.

Among other duties on her current mission, Whitson is helping NASA identify some of the health problems that astronauts develop during extended stays in conditions of apparent weightlessness called microgravity. Such information will be useful in preparing for lengthy missions to Mars or for life at an extraterrestrial base.

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A Unique Martian Potato

2017-05-03T09:14:00-05:00

Scientists at the International Potato Center in Lima, Peru, grew a “Unique” potato in simulated Martian conditions within the container at left, called the “CubeSat.” Credit: © International Potato Center

In Andy Weir’s 2011 book The Martian and its 2015 film adaptation, botanist-astronaut Mark Watney manages to grow potatoes while marooned on Mars. Watney hauls Martian soil into a pressurized, climate-controlled base and harvests a crop that provides food while his other supplies run out. Today, a group of Peruvian scientists are working on transferring this fiction to reality. Agricultural researchers from the International Potato Center (called the Centro Internacional de la Papa in Spanish, or CIP) in Lima, the Peruvian capital, have grown some rather hardy potatoes in an even worse environment than Watney’s Martian garden. The scientists’ research, carried out in the Andes Mountains of South America (where potatoes originated), might make farming on Mars or other barren places possible.

Human exploration of Mars is one of the primary long-term goals of such space agencies as the United States National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA). But before people get there, scientists must solve a host of problems. First among them will be how to feed astronauts during an extended stay in the harsh environment of the Red Planet.

Potatoes originated in the often harsh environment of the Andean Highlands of South America. Credit: © Roux Frederic, Shutterstock

The ability to grow food during a space journey or while on the Martian surface has a number of benefits. Space could be saved in the spacecraft, allowing for other needed supplies, and instead of freeze-dried or tubular “astronaut food,” space explorers could eat a variety of freshly grown produce. But growing food on Mars—an extremely cold, dry, and nearly airless planet—will not be easy. Life as we know it cannot survive on its surface—yet.

The ability to grow food on Mars will greatly help in the planet’s exploration and possible settlement. Credit: NASA/JPL/Malin Space Science Systems

In Peru, the CIP scientists wanted to see if certain hardy potatoes could be grown in conditions similar to those found on Mars. To do this, the scientists built a sealed growing chamber (a garden in a box they called a “CubeSat”) and layered it with nutrient-weak, sandy soil similar to that found on Mars. They installed low-powered lights on a longer-than-Earth day-night cycle, and created a low-temperature and low-atmospheric pressure environment. They then tried growing dozens of varieties of potatoes in the simulator, irrigating them with nutrient-rich water. Of all the tested varieties, one called “Unique” grew best under the extreme conditions.

The Unique potato is exceptionally hardy, but it could not possibly grow on the surface of Mars without human intervention. The scientists grew the potatoes at temperatures around freezing, but surface temperatures on Mars can dip below -150 °F (-100 °C) at night. They were able to achieve growth with somewhat reduced atmospheric pressure (like the thin air at the top of the Andes Mountains), but Mars’s atmospheric pressure is a mere 0.7 percent of the atmospheric pressure on Earth. And, as far as we know, there is no nutrient-rich water on Mars. Liquid water near the Martian surface is only present during the planet’s summer, and it is extremely salty.

Potatoes are one of the world’s most important crops. The ability to grow potatoes and other crops in harsh conditions could prove vastly important as climate change alters the global environment. Credit: © David R. Frazier

The CIS experiment provided scientists and engineers with useful information on the extreme limits of vegetable cultivation. With the use of extremely hardy plants like the Unique potato, astronaut greenhouses could be kept cooler than Earth spaces, saving valuable electricity for purposes other than heating. Because plants can survive on carbon dioxide concentrations, excess carbon dioxide exhaled by astronauts could help provide the space garden’s protected atmosphere. If Martian soil could be manipulated for vegetable growth, it would negate the need to send bundles of Earth soil to the Red Planet.

Beyond its applications to space travel or Martian living, the CIS potato research has a more practical use here on Earth. As the climate changes from global warming, environmental conditions will become harsher in many places around the world. By studying how crops survive in extreme conditions, agricultural scientists may be able to discover and breed crops more resistant to the worst effects of climate change.

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Rocket Recycling

2017-04-18T10:31:00-05:00

A recycled SpaceX Falcon 9 rocket launches from Florida’s Kennedy Space Center on March 30, 2017. Credit: SpaceX

Late last month, Space Exploration Technologies Corporation (commonly called SpaceX) made aerospace history. After propelling a communication satellite into orbit, the first stage of one of the company’s Falcon 9 rockets landed on a drone ship (uncrewed barge) in the Atlantic Ocean. But this booster had been there before. SpaceX successfully reused a booster that had been launched during a previous mission. The achievement has been widely hailed as the dawn of a new era in commercial spaceflight.

A rocket is a type of engine that pushes itself forward or upward by producing thrust. Unlike a jet engine, which draws in outside air, a rocket engine uses only the substances carried within it. As a result, a rocket can operate in outer space, where there is no air.

SpaceX is a private space exploration company founded by South African entrepreneur (business developer) Elon Musk. On March 30, one of the company’s multistage Falcon 9 rockets lifted off from Kennedy Space Center in Florida. In a traditional multistage rocket, discarded stages fall to Earth or burn up in the atmosphere. In recent SpaceX launches, however, the first stages of Falcon 9’s descend either to a landing pad or a floating drone ship and land vertically–and safely. The first stage in question had been used during an April 2016 mission and, on that first mission, was the first booster to land on a ship at sea. For this year’s mission, it again landed successfully on the drone ship Of Course I Still Love You. SpaceX also recovered part of the Falcon 9's fairings, the nosecone sections that protect the payload. The recovered section, measuring 43 feet (13 meters) long and 17 feet (5 meters) in diameter, splashed down via parachute not far from the drone ship. It can also be reused, saving millions of dollars.

Engineers have toyed with reusing rockets before. Notably, the United States space shuttles were partly reusable. These airplane-like orbiters could land on a runway and be reused, and the boosters were towed back to land by ships and were refurbished. But each orbiter had to be extensively examined and repaired after each flight. Even with such precautions, booster failure and heat shield damage destroyed orbiters in 1986 and again in 2003, killing 14 astronauts together. The shuttle program, which ran from 1981 to 2011, made just over 100 flights and cost over $200 billion—far more than traditional rockets would have cost to fly the same number of missions.

Learning from the failures of the space shuttle program, many new private space companies have based their business models on reusability. Blue Origin, a rocket company owned by American businessman Jeff Bezos, has successfully landed and reused stages of its experimental New Glenn rocket, with an eye toward both commercial satellite launches and space tourism. Virgin Galactic, a company founded by British businessman Richard Branson, is testing a space-tourism rocket that is released from a special airplane and lands on an Earth-bound runway like the space shuttle orbiters did.

Reusability has the potential to make spaceflight far cheaper than it is today. Imagine if, after one flight, an airplane had to be thrown away. Air travel would be incredibly expensive. Reuse of rocket parts will allow satellites to be launched more cheaply and will make space travel accessible to tourists–albeit wealthy ones. By reusing the first stage and fairings, it is estimated that SpaceX could cut costs by 70 percent.

Musk has already outlined the company’s next goal: he wants to fly two missions with the same booster within 24 hours. It took almost a year for SpaceX to examine and refurbish this booster, but Musk is confident that the lessons learned will both speed up the refurbishment process and inform the design of the next version of the Falcon 9, which is scheduled to fly within the next year.

Despite the enormity of this achievement, Musk has stated that true success will come when these launches become automatic. When it becomes routine to recover and reuse rocket parts, the true potential of spaceflight may soon be realized.

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Supernova Spotting

2017-03-02T10:43:00-06:00

^Top image: Supernova 1604 was a star that exploded in our own galaxy. The supernova blasted off the shell of gas and dust seen in this false-color composite image. The shell continues to expand at around 2,000 kilometers (1,200 miles) per second. The German astronomer Johannes Kepler observed the explosion in 1604. Credit: NASA/ESA/JHU/R. Sankrit & W. Blair

Time operates on an epic scale among the stars and galaxies of outer space. Some stars exist for millions of years but then suddenly undergo rapid changes and explode within months. In October 2013, an international team of scientists lead by Ofer Yaron, an astrophysicist at the Weizmann Institute of Science in Israel, detected and studied a supernova that occurred in a distant galaxy within three hours of the explosion’s light first reaching Earth. Thanks to the timely observations, the team was able to learn a lot about the star and the explosion that consumed it. The team published its findings in February 2017 in the journal Nature Physics.

A supernova is an exploding star that can become billions of times as bright as our sun before gradually fading from view. At its brightest, a supernova may outshine an entire galaxy. The explosion throws a large cloud of gas into space at speeds of up to 10 percent of the speed of light, which is 186,282 miles (299,792 kilometers) per second. The mass of the expelled material may exceed 10 times the sun’s mass. Most supernovae reach their peak brightness in one to three weeks and shine intensely for several months.

A red supergiant called V838 Monocerotis glows at the center of a dust cloud in this photograph taken by the Hubble Space Telescope. In 2002, the star gave off a brilliant flash of light, becoming 600,000 times as bright as the sun. The flash illuminated dust thrown off the star during a previous outburst. Credit: NASA/ESA/H.E. Bond (STScI)

The exploding star examined by Yaron and his associates was a red supergiant. Such stars are dozens of times larger than our sun, which is a main sequence star or yellow dwarf. Red supergiants have relatively short life spans, however, existing for “only” millions of years. In contrast, our sun is expected to live some 10 billion years. All stars produce energy through the process of nuclear fusion, a joining of two atomic nuclei (cores) to produce a larger nucleus. Fusion releases a huge amount of energy. Most stars fuse hydrogen or helium, but a supergiant quickly (over millions of years) burns through its fuel supply and begins to fuse heavier elements together in its core. At this point, a supergiant’s days are numbered. Each new level of fusion chips away at its core, slowly killing the star. At a critical point, the star quickly fuses its available silicon into iron. Once the core fills with iron, the star will collapse and rebound in an explosive supernova.

A huge star creates chemical elements by nuclear fusion, the joining of two atomic nuclei to make a larger nucleus. In the outermost shell, hydrogen nuclei fuse, creating helium. In the next shell, helium fuses to make carbon and oxygen. Fusion creates successively heavier elements in shells closer to the core, where iron is produced. Credit: WORLD BOOK diagram

Based on the patterns of light emitted by the supernova in question, Yaron and the team discovered that the star had blown off a layer of material into space about a year before the explosion. They suspect that this layer has to do with a change in fusion fuel at the star’s core shortly before it went supernova. The transition itself was violent, setting off a chain reaction within the star that shot a layer of star matter into space ahead of the supernova.

The discovery was made with the help of an ever-improving array of automated survey telescopes. Such telescopes capture images of a certain portion of the night sky. A computer then compares the images against earlier pictures of the same section of sky, looking for changes. If it detects any, the computer alerts a human astronomer to investigate the findings.

Astronomers are eagerly awaiting the next supernova to occur in the Milky Way. They estimate that a supernova occurs once every 100 years or so in our galaxy, but they are not always visible to Earth-bound observers. The last local supernova seen on Earth occurred in 1604, when German astronomer Johannes Kepler observed what he thought was a new star in the night sky. The most recent intragalactic (within our galaxy) supernova occurred around 1900, but its light was obscured by dust. Scientists were only able to study it 100 years later with instruments such as the orbiting Chandra X-Ray Observatory and the National Radio Astronomy Observatory’s Very Large Array near Socorro, New Mexico. If we’re lucky enough for the next supernova to be close (but not too close), we can learn more about the largest stars and the brilliant ends of their lives.

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How Many Moonlets to a Moon?

2017-02-03T14:16:00-06:00

One of the greatest questions in the formation of the solar system is in our own planetary back yard: how was the moon made? The current hypothesis (proposed explanation)—that the moon formed from chunks of Earth unloosed in a massive collision—has held sway among planetary scientists for over 30 years. But as more is learned about the moon, scientists are exploring other possibilities, and three scientists in particular—Raluca Rufu and Oded Aharonson of the Weizmann Institute of Science, Israel, and Hagai B. Perets of the Technion Israel Institute of Technology—are offering a different explanation. They published their new theory last month in the journal Nature Geoscience.

Since the early days of astronomy, people have speculated on how the moon was formed. In the 1800’s, astronomers used to think that the moon split from Earth—but in a very peculiar way. The accepted hypothesis of that era said that in the distant past Earth spun so rapidly that a portion of it tore away, forming the moon and leaving behind a basin that became the Pacific Ocean. Scientists now know that plate tectonics formed the Pacific Ocean over hundreds of millions of years, and that Earth lacks the rotational speed to create such a spectacular split. In recent years, engineers have developed powerful computers that allow geologists to take new and closer looks at rocks returned from the Apollo moonlandings from 1969 to 1972.

Since the 1980’s, one hypothesis has stood up best to scrutiny: that the moon formed as a result of a massive collision known as the Giant Impact or the “Big Whack.” According to this idea, a Mars-sized object collided with Earth about 4.6 billion years ago. As a result of the impact, a huge cloud of vaporized rock shot off Earth’s surface and went into orbit around Earth. The cloud cooled and condensed into a ring of small, solid bodies, which then gathered together, forming the moon.

If the Big Whack is favored, why are Rufu, Aharonson, and Perets exploring alternative ideas? The Big Whack explains many of the orbital and rotational characteristics of both Earth and the moon, but the hypothesis must be tweaked to an uncomfortable degree to account for the remarkable similarity of Earth rocks to moon rocks. The giant impactor would have had to have struck Earth in an extremely precise way to produce a moon with the makeup shown by returned lunar samples.

Therefore, the Israeli team started from scratch. They reasoned that becuase impacts were common in the early solar system, Earth should have been hit with objects large enough to create moons many times, not just once. They ran hundreds of computer simulations and found that a series of smaller impacts over the course of millions of years could explain the compositional similarity of Earth and its moon. A smaller body (more the size of the dwarf planet Ceres) would slam into Earth, forming a disk of debris that would eventually come together to form a moonlet, or mini-moon. Later, another body would collide with Earth, creating a new debris disk and another moonlet. Eventually, these moonlets would merge with one another. To reach the size of the current moon, a number of such collisions and moonlet creations and mergings (their guess was roughly 20) would be needed.

The new study is intriguing, but it does not disqualify the Giant Impact Hypothesis just yet. Rufu and her colleagues admit that much more research needs to be done to confirm their findings. For instance, the group did not determine if some of the moonlets could have been sucked back into Earth or flung out into the solar system. This would increase the number of impacts needed to make our moon, making this explanation less likely than a precise Giant Impact.

Image one: A new theory suggests that the moon may have formed from debris unloosed by many small impacts on Earth rather than one big one. Credit: Lunar and Planetary Institute

Image two: This artist rendering depicts the “Big Whack” hypothesis of Earth colliding with a planetary body. The resulting dust and debris from Earth would then have created the moon. (Credit: NASA/JPL-Caltech)

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ExoMars Good and Bad

2016-11-03T11:10:00-05:00

^Top image: This artist’s impression shows the Trace Gas Orbiter and Schiaparelli (the small circular knob facing toward Mars) during the seven-month ExoMars voyage to the Red Planet. Credit: ESA/David Ducros

Last month, on October 19, Mars claimed another victim. A landing module named Schiaparelli, designed by the European Space Agency (ESA) and Russia’s space agency, Roscosmos, accidentally smashed into the Martian surface at more than 180 miles (300 kilometers) per hour. Schiaparelli (named for the Italian astronomer Giovanni Schiaparelli, who studied Mars in the late 1800's) was destroyed, but the mission was not a total failure. The Mars Trace Gas Orbiter (TGO), launched with Schiaparelli, successfully entered into orbit around the Red Planet.

Despite is relatively inviting appearance, Mars is extremely difficult to explore. Of all the missions sent there, nearly two-thirds have failed before completing their planned experiments and observations. Landing on Mars is particularly difficult. The planet’s atmosphere is extremely thin, which means that parachutes and similar braking devices don’t work as well as they do in the much denser atmosphere of Earth. Mars is also a relatively large planet, and its significant gravitational pull forces a lander to carry large amounts of fuel for its rockets to slow the descent. On the surface, craggy rocks, enormous sandstorms, and frigid temperatures conspire to damage a lander as it settles into a safe resting place.

The ESA and Roscosmos launched ExoMars 2016, which consisted of Schiaparelli and the TGO, in March of this year. The lander was equipped with a parachute and rockets to slow its entry through the Martian atmosphere. The parachute deployed, but it ejected far too soon. To make matters worse, the rockets, which were supposed to fire for about 30 seconds, fired for only a few seconds before shutting off. Project engineers think these malfunctions stemmed from a software glitch that led the lander to act as though it was already on the Martian surface. Instead, it was actually plummeting through the Martian atmosphere. With nothing to slow it, Schiaparelli crashed into the Red Planet’s surface and exploded.

ExoMars 2016 did not function as the European scientists had hoped, but it could still be a successful mission. Schiaparelli was not intended to add much to the science output of the mission. It had enough power to survive only a few Martian days. Its primary objective was to demonstrate landing technology for the ambitious ExoMars 2020, which will attempt to land a rover on Mars. Mission leaders can take heart in the fact that the lander seems to have been doomed by a software failure, a problem much easier to fix than a hardware failure. But it will be small consolation to an ExoMars program that is already behind schedule and over budget.

The Trace Gas Orbiter, however–a crucial part of the future ExoMars mission–entered into orbit around Mars and appears to be functioning normally. The TGO will examine methane and other gases in the Martian atmosphere. It will help determine if this methane is the result of geological or biological processes. Scientists have not found direct evidence of life on Mars, but some think tiny organisms could exist below its surface. The TGO will also serve as a data relay center for the ExoMars 2020 rover, receiving commands from Earth for the rover and data from the rover to be sent back to Earth. Let’s just hope ESA and Roscosmos can stick the landing on the next try!

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Mapping the Milky Way

2016-09-23T10:32:00-05:00

^This artist’s impression shows Gaia mapping the stars of the Milky Way. Credit: ESA/ATG medialab/ESO/S. Brunier

The Milky Way Galaxy is our home, but we know surprisingly little about it. Last week, on September 14, the European Space Agency (ESA) released a wealth of data gathered by the space probe Gaia (named after the ancient Greek goddess Gaia). The probe pinned down the precise position and brightness of over a billion stars. As massive as this dataset seems, it represents just a taste of what is to come from Gaia, which promises to revolutionize the study of our galaxy in the next several years.

Because our solar system is located within the Milky Way, vast clouds of dust and dense swaths of stars prevent astronomers from determining the galaxy’s exact structure. It’s a bit like trying to figure out what the outside of one’s home looks like while being trapped inside. Until now, astronomers had to guess what the Milky Way looks like by observing other galaxies with similar traits—the equivalent of looking at other houses from a window. Gaia, however, is like a drone taking photos around the neighborhood. Launched in 2013 by the ESA, Gaia traveled to a point behind Earth and began measuring the positions of over a billion stars as it orbited the sun.

Gaia measures stellar distances using a technique called parallax. It first images a star against a background of other stars. Halfway around the sun, it takes another picture of the same star. Because the two pictures are taken many millions of miles apart, the star’s position changes slightly in relation to its background. This is the same effect that causes an object at arm’s length to appear to change positions when viewed from one eye or the other at a time. Because scientists know how far away the two star pictures were taken, and how much the star appeared to move, they can calculate its distance from Earth.

Gaia’s first map shows a two-dimensional plot of star density in the Milky Way. As Gaia orbits the sun, it will gather information on more and more points of light. It will then be able to refine its data to better define star positions. Astronomers are confident that future data from Gaia will allow them to create extremely accurate, three-dimensional maps of the galaxy.

Furthermore, as Gaia’s mission continues, its portrait of the Milky Way will extend into four dimensions (including time). As it observes over the years, Gaia will be able to detect the speed and direction in which stars are moving through space. This information will allow astrophysicists to see what the galaxy looked like in the recent past and to predict what it will look like in the near future.

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The Pale Red Dot: Proxima b

2016-08-31T11:24:00-05:00

^Top image: This artist’s impression shows the red dwarf star Proxima Centauri, the closest star to our solar system, on the red horizon of Proxima b, a planet scientists think could support life. The double star Alpha Centauri AB appears to the upper right of Proxima Centauri. Credit: ESO/M. Kornmesser

On August 24, scientists from the European Southern Observatory (ESO) announced that they had discovered an extrasolar (beyond our solar system) planet, or exoplanet, that may harbor conditions favorable to life. This exoplanet, called Proxima b, orbits Proxima Centauri, the star closest to the sun. Astronomers have nicknamed Proxima b the “pale red dot,” a play on Earth’s appearance as a “pale blue dot” in a distant photo taken by the Voyager 1 space probe in 1990. Astronomers believe that Proxima Centauri, a red dwarf star, will cast its close-orbiting planet in a pale red glow. The search for a planet orbiting Proxima Centauri, which began just seven months ago, was dubbed the “Pale Red Dot” campaign.

Proxima Centauri is part of a three-star system called Alpha Centauri. Two of the stars, Centauri A and Centauri B, are roughly the size of the sun and orbit each other. Proxima Centauri is a much smaller red dwarf star and orbits the larger pair of stars every million years or so.

^Proxima b (nicknamed the “pale red dot” by astronomers) and its orbit around Proxima Centauri are compared with the same region of our own solar system. Proxima Centauri is smaller and cooler than the sun, and Proxima b orbits much closer to its star than Mercury orbits the sun. A planet in the green habitable zone could possibly have liquid water, which could possibly support life. Credit: ESO/M. Kornmesser/G. Coleman

The newly discovered exoplanet, Proxima b, is at least 1.3 times the size of Earth. Its size indicates that it is probably a rocky planet, like Earth and Mars. It orbits Proxima every 11 Earth days (Mercury, the closest planet to the sun, completes a year every 88 Earth days). If Proxima Centauri were a star like our sun, the planet would be little more than a charred husk. But red dwarf stars are small and relatively cool. Consequently, it is possible that liquid water could exist on the exoplanet’s surface. Scientists call this region around a star, where temperatures are suitable for liquid water, its habitable zone. Liquid water is a necessary building block for life as we know it.

If red dwarf stars can harbor habitable worlds, then the odds that life exists elsewhere in the universe increase significantly. Red dwarfs make up about 70 percent of the stars in the universe. They also burn slowly and steadily, for up to 10 trillion years. In contrast, the sun has a stable lifespan of only 10 billion years. As a result, if favorable conditions exist, life could have countless chances to form over countless eons.

Astronomers still have a lot to learn about Proxima b and whether it can host life. It might lack an atmosphere or get bombarded by powerful X ray blasts from Proxima. The James Webb Space Telescope (JWST), to be launched in 2018, should answer some of these questions. It will be able to determine the exoplanet’s composition and whether it has an atmosphere. JWST will also gather more information on the planet’s size and makeup. Future space telescopes may even be powerful enough to see the “pale red dot” directly.

Most exoplanets are too far away to be explored by spacecraft from Earth. They orbit stars many light-years away. A light-year is the distance light travels in a year, or about 5.88 trillion miles (9.46 trillion kilometers). Nothing can travel faster than the speed of light. Proxima Centauri, however, is just 4.2 light-years away, tantalizingly close in astronomical terms. But the fastest spacecraft ever created have reached just tiny fractions of the speed of light. Using such technology, a traditional space probe would still take thousands of years to reach the system.

A private initiative called Breakthrough Starshot, however, has proposed launching a tiny spacecraft to the system that would take as little as 20 years to get there. The probe would be only a gram or two (the equivalent of less than an ounce on Earth) and be propelled by large Earth-based lasers to 20 percent of the speed of light. There are many technical hurdles to be overcome, however, and the group does not anticipate launching a probe for at least another 20 years, but there is hope that the planet could be explored close-up before 2100. Soon, we may get to say hello to our closest potential neighbor. Will it say hi back?

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A Frankenstein Galaxy of Spare Parts

2016-08-10T12:09:00-05:00

Photo: At left, in optical light, UGC 1382 appears to be a simple elliptical galaxy. But spiral arms emerged when astronomers incorporated ultraviolet and deep optical data (middle). Combining that with a view of low-density hydrogen gas (shown in green at right), scientists discovered that UGC 1382 is huge, about 718,000 light-years wide.
Credit: NASA/JPL/Caltech/SDSS/NRAO

In a sleepy section of the visible universe there lurks a huge galaxy with a bizarre patchwork of features. The galaxy was known to astronomers, but its large size and strange attributes went unnoticed for decades. Research spearheaded by Lea Hagan, a graduate student at Pennsylvania State University, University Park, has found there is more to galaxy UGC 1382 than meets the eye. Hagen and her colleagues published their findings last month in The Astrophysical Journal.

A galaxy is a vast system of stars, gas, dust, and other matter held together in space by their mutual gravitational pull. Astronomers classify galaxies into three main types based on shape: (1) spiral galaxies, (2) elliptical galaxies, and (3) irregular galaxies. Spiral galaxies feature a thin, disklike structure with sweeping arms of stars wrapped about the galaxy’s center. Elliptical galaxies have forms like centrally concentrated spheres or flattened globes. Irregular galaxies are those that don’t have spiral or elliptical forms.

In visible-light images, UGC 1382 appears to be a modestly sized elliptical galaxy, uninteresting to all but the most serious astronomer.Ultraviolet images of the galaxy gathered by the orbiting Galaxy Evolution Explorer (GALEX) telescope, however, hinted that UGC 1382 had a more complicated structure. Hagen and her team noticed previously unseen huge spiral arms billowing out from the elliptical center. The team then used observations from other telescopes to learn more about this mysterious galaxy.

Hagen’s team found that UGC 1382 is over 700,000 light-years across with its spiral arms. A light-year is the distance light travels in a year in the vacuum of space, or about 5.88 trillion miles (9.46 trillion kilometers). The Milky Way, the spiral galaxy that contains our solar system, is only about 100,000 light-years across. The scientists also found UGC 1382 to possess a puzzling structure. They determined that the stars in the spiral arms are older than the stars in the galaxy’s bright core. This arrangement is opposite of what is seen in most spiral galaxies.

The team thinks that this odd formation arose from the combination of several galaxies long ago. Billions of years ago, a group of small galaxies formed, containing much gas and dark matter. Dark matter is a substance thought to make up most of the matter in the universe but does not give off, reflect, or absorb light rays. Much later, a kind of elliptical galaxy called a lenticular galaxy formed near the group. A lenticular galaxy spins, but has no spiral arms. This galaxy floated through the group of older galaxies. The lenticular galaxy’s gravity warped and pulled at the older galaxies, eventually twisting them around itself to form spiral arms. Because these galaxies were composed mostly of gas and dark matter, the spiral arms are dim and do not appear in visible-light images of UGC 1382.

Hagen and her colleagues think this kind of galaxy could only form in emptier sections of the universe, without gravitational interference from other galaxies. They hope to do more research to better understand UGC 1382, a sort “Frankenstein” galaxy cobbled together from cosmic spare parts, and to find more oddball galaxies that are stranger than they first appeared

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