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  • A Frisbee-shaped disk of dust with a star in the middle begins to pass in front of the giant star Epsilon Aurigae in this artist's concept. The system's light fades every 27 years, and remains dim for two full years. This model best explains that odd behavior. [NASA/JPL/Caltech] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • It’s not unusual for a star to change brightness over a period of days, months, or even years. In many cases, such a star is actually a binary — two stars bound by gravity. The stars periodically pass in front of each other, eclipsing some of the system’s light. But Epsilon Aurigae takes things to the extreme. Its light fades once every 27 years, and the star remains dim for two full years. The most recent of its eclipses ended in August of 2011. Astronomers kept an eye on it with telescopes on the ground and in space. Their observations helped refine the explanation for this odd system. Although Epsilon Aurigae is a binary, we see only one of its stars. It’s more than a hundred times wider than the Sun, and tens of thousands of times brighter. The other star is embedded in a cocoon of dust that forms a disk, like a Frisbee. Once every 27 years, the disk passes in front of the bright star, creating a two-year eclipse that cuts the system’s brightness by half. The star inside the disk is probably heavier than the visible star. It’s blowing a thick “wind” of gas from its surface. Out in space, the atoms cool and stick together to form solid grains, which hide the star from view. Epsilon Aurigae is in Auriga, the charioteer, which is in the northeast this evening. Look for its brightest star, brilliant Capella. Epsilon Aurigae is close to its right. It’s fairly bright — and will remain so until the next eclipse begins in 2036.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Beautiful Cassiopeia circles high across the northern sky on autumn evenings. Its brightest stars form a letter M or W. The constellation has played a prominent role in the skylore of many cultures. In western culture, it represented the mythological queen of Ethiopia. And in ancient China, it represented a four-horse chariot driven by a famous warrior, Wang Liang. A real historical figure, he lived in the fifth century B.C., and was particularly known for his integrity. In his honor, astronomers named the star at the bottom left point of the “M” for the warrior himself — “the first star of Wang Liang.” Four other stars in the pattern represented the chariot’s horses. They were known as Wang Liang Er, San, Si, and Wu — “the second, third, fourth, and fifth stars of Wang Liang.” And one more was named Tsih, from the Mandarin word for riding whip. The constellation is close enough to the Pole Star that it never sets as seen from most of the United States. But it does circle around the Pole Star to different positions at different times of the year. Right now, it’s high in the northeast as night falls, so you can see it as either an M or a W. A few hours later, though, it stands due north, at its highest point in the sky. From that angle, it’s hard to see anything but a letter M — a beautiful pattern of stars associated with some ancient stories. Tomorrow: Stellar Frisbee.   Script by Robert Tindol and Paris Liu, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Hubble Space Telescope has been peering deep into the universe for almost a quarter of a century. Among many accomplishments, its observations have demonstrated that the universe is expanding faster as it ages. That the universe is expanding at all was established by the telescope’s namesake, Edwin Hubble, who was born 125 years ago this week. Hubble earned his doctorate in astronomy during World War I, then joined the army and was sent to France. When he came home, a job was waiting for him at Mount Wilson Observatory in California. The observatory had just built the world’s largest telescope, and Hubble used it to study the whorls of matter known as nebulae. At the time, some thought these objects were all inside the Milky Way, while others thought that some of them were separate galaxies of stars far beyond the Milky Way. Hubble discovered a pulsating star in the Andromeda Nebula. The length of the star’s pulses revealed its true brightness, which Hubble used to calculate its distance: about a million light-years — confirming that the Milky Way is just one of many galaxies in a vast universe. Later, Hubble reported something even more astonishing: The farther away a galaxy is, the faster it’s moving away from us. This implied that space itself is expanding — early evidence of the Big Bang. These discoveries made Hubble famous — a fame that became even greater when NASA named its first great space observatory in his honor.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • [AUDIO: 3, 2, 1, and liftoff of space shuttle Atlantis on the final visit to enhance the vision of Hubble...] When Atlantis headed toward Hubble Space Telescope back in 2009, its cargo included a basketball that the University of Chicago had used in a game against Indiana exactly a century earlier. One of the Chicago stars that year was a lanky 6-2 forward: Edwin Hubble, the namesake of Hubble Space Telescope. Hubble was born 125 years ago today in Missouri. He was bright and athletic, and set records in high school track and field events. He was interested in science — especially astronomy — but he promised his father he’d pursue a career in law. So after earning a science degree at the University of Chicago — as well as two Big Ten basketball titles — Hubble journeyed to Oxford. He earned his law degree there, and after the death of his father in 1913, he returned to the United States to help take care of his family. Although he passed his bar exams, Hubble wasn’t interested in law. Instead, he taught high school physics and Spanish for a while before returning to college to pursue his true interest: astronomy. He finished his PhD shortly after the U.S. entered World War I, and enlisted in the army the same day. After the war, Hubble had a job waiting for him at Mount Wilson Observatory in California. He used the world’s largest telescope there to make some of the most important discoveries of the 20th century. More about that tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Before he became a world-famous astronomer, Edwin Hubble (left) was an accomplished basketball player and track star in high school and at the University of Chicago. In 2009, space shuttle Atlantis carried a basketball used in one of Hubble's games (right) on the final mission to serve Hubble Space Telescope, which is visible outside the shuttle's windows. [NASA] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • At the start of the 20th century, many astronomers thought the universe consisted only of our home galaxy, the Milky Way. But observations by Edwin Hubble and others found that the universe extends far beyond the Milky Way, and encompasses billions of galaxies. Hubble’s observations also showed that the farther away a galaxy is — in any direction — the faster it’s moving away from us. If the galaxies were all moving away from each other, that meant that something had to set them in motion. And that realization led to a new theory about the birth of the universe: the Big Bang. Big Bang cosmology says that the universe began from a tiny volume. It began expanding 13.8 billion years ago, creating space itself and filling it with matter and energy. The Big Bang is supported by many discoveries over the past century, beginning with the expanding universe. Other evidence includes the presence of a background glow that comes from all directions — the “afterglow” of the Big Bang itself. Another bit of evidence is the chemistry of the universe. Most “normal” matter consists of hydrogen and helium, the two simplest elements. These were forged shortly after the Big Bang, when the universe was incredibly hot and dense. But the universe expanded and cooled too quickly to make heavier elements. Instead, those have been forged inside stars from the original hydrogen and helium — products of the Big Bang. More about Edwin Hubble tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • This image shows a portion of the sky as seen by COBE, a satellite launched 25 years ago. It measured the "afterglow" of the Big Bang, which fills the universe with microwaves. Tiny variations in the temperature of this glow, shown in red and blue, show regions of different density. The denser concentrations of matter gave birth to the first stars and galaxies. COBE's top scientists later won the Nobel Prize for the craft's observations. [NASA/GSFC] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • In the days before remote controls and cable TV, changing the channel often took you through unused channels filled with static. Most of that static came from the afterglow of the Big Bang — a background energy that fills the universe. It was first studied in detail by a spacecraft that was launched 25 years ago today. Big Bang theory says the early universe was incredibly hot and dense. As it expanded, it cooled. We can still see the energy produced by that early period, though, as a microwave glow that comes from every direction in the sky. Scientists discovered that glow in 1964. Early observations found absolutely no variations in it — it looked exactly the same in every direction. But that was a problem. It was hard to explain how such a smooth early universe could give rise to the “lumpy” modern universe, which is filled with galaxies and clusters of galaxies. COBE — the Cosmic Background Explorer — was designed to look for tiny variations in the microwave background. And it found them. They amounted to only about one part in 20,000. Yet they represented the first structure in the universe — filaments of hot gas that clumped around strands of “dark matter.” Much of the gas eventually coalesced to form stars and galaxies — the universe we see today. COBE’s creators received the Nobel Prize for their work — studying the afterglow of the Big Bang. More about the Big Bang tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • On the grandest of scales, the universe is like a spider web. Strands of galaxies can stretch across a billion light-years or more, separated by wide spaces known as cosmic voids. The first big strand in the web was reported 25 years ago today. Known as the Great Wall, it’s hundreds of millions of light-years long and contains tens of thousands of galaxies. The wall was discovered by Margaret Geller and colleagues at the Harvard-Smithsonian Center for Astrophysics. They were producing three-dimensional maps of how galaxies are distributed — not just where they appear in the sky, but how far away they are as well. Their first plots revealed a shape that resembled the stick figure of a man, with a thick body and spindly arms and legs. The “body” was the Great Wall — a dense ribbon of clusters and super clusters of galaxies that’s a few hundred million light-years away. Before the Great Wall, it was generally thought that galaxy clusters were pretty evenly spread. But the Great Wall and similar streamers of galaxies found since then show that’s not the case — there’s a large-scale structure in the way galaxies are distributed. That structure is provided by invisible ribbons of dark matter, which pulled in the normal matter around them to make galaxies. In fact, hints of those ribbons were first seen by a space telescope that was launched the day after the discovery of the Great Wall was published. More about that tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A “streaky” meteor shower will be at its best over the next couple of nights. Unfortunately, this won’t be one of its better years. Even so, it should produce a “shooting star” every few minutes. The best view comes in the wee hours of the morning, when the shower’s namesake constellation climbs into view — Leo, the lion. If you trace the paths of the meteors across the sky, they all appear to come from Leo, so the shower is known as the Leonids. The meteors are created by bits of rocky debris from a comet that orbits the Sun once every third of a century. Earth intersects the trail of comet dust every November. The bits of debris ram into the atmosphere at tens of thousands of miles an hour. They quickly vaporize, forming the glowing streaks known as meteors. The trail is clumpy, though, with the biggest clumps near the comet itself. So every time the comet streaks through the inner solar system, the number of meteors goes up. Some years, the Leonids can produce hundreds of meteors an hour. And some years, the Leonids produce not showers of meteors, but storms. In 1833, for example, so many meteors streaked across the sky that their light awakened sleeping Americans. And in 1966, the Leonids produced up to 50 meteors every second across parts of the southwest. This won’t be one of those great years. Even so, the shower could still be worth a look as it reaches its peak in the wee hours of tomorrow and Tuesday.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Today’s culture offers us plenty of celebrities who are famous just for being famous. Everybody knows about them even if they’re not especially talented or even bright. The night sky offers a few of those celebrities as well — constellations that aren’t especially bright or easy to spot, but that are famous nonetheless. A prime example is Aries, the ram. It’s low in the east at nightfall and soars high across the south in late evening. It’s a faint pattern marked by only a couple of moderately bright stars: Hamal, its brightest, and Sheratan, its second-brightest. There’s not much around the stars to point them out, though, so you might want a star chart to find them. Aries is famous not because of its brilliance, but because of its location — it’s one of the constellations of the zodiac. These constellations all lie along the Sun’s path across the sky. In ancient times, that gave them special significance. Aries was the most significant of all. At the time the constellations were named, the Sun appeared against its stars at the vernal equinox — the first day of spring in the northern hemisphere. With the earth awakening from its winter slumber, the equinox was a time of celebration. And it often marked the beginning of a new year. Today, the Sun’s location at the equinox is still known as the “first point of Aries,” even though the Sun is actually in Pisces — another faint constellation that’s famous for being famous.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Philae snapped this view of its landing site on Comet Churyumov-Gerasimenko shortly after touching down on November 12. The systems designed to pin Philae to the surface failed, so the lander bounced roughly one kilometer high, then bounced a second time before settling onto the comet roughly two hours later than planned. It settled at the base of a cliff that blocks sunlight for much of the comet's "day." Without sunlight the probe cannot recharge its solar batteries, so it may operate for only a few days. [ESA/Rosetta] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A couple of bright companions lurk near the Moon at dawn tomorrow. The star Regulus, the bright heart of Leo, the lion, stands above the Moon. And the brilliant planet Jupiter is off to their upper right. The star we see as Regulus is bigger, brighter, and heavier than the Sun. But it has at least three companion stars. One of them is only a few million miles from Regulus. It’s the dead core of a star that was once much more impressive than Regulus itself. In fact, it probably dumped much of its gas onto Regulus, making it the dominant member of this close duo. The other two companions also form a pair. But they’re so far away from Regulus that it takes more than three weeks for light to cross the wide gulf between them. These stars have attracted much less attention than their brilliant sibling. Astronomers know that one of the stars — Regulus B — is a little smaller and fainter than the Sun, but not much else. And the other member of the pair — Regulus C — is even less well known. It’s a red dwarf — a faint cosmic ember that’s only a fraction as big, bright, and heavy as the Sun. But no one has compiled much of a profile of the star, so its details are sketchy. The two stars are separated by about a hundred times the distance from Earth to the Sun, so it takes centuries for them to complete a single orbit around each other — two faint, overlooked companions to the mighty heart of the lion.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Some of the smaller moons of Jupiter could use a good vacuum cleaner. They shed grains of dust, which form dark rings around the giant planet. Jupiter’s rings are insignificant compared to those of Saturn. In fact, they’re so faint that they weren’t discovered until 1979, when a spacecraft flew past the planet. There are four bands of rings. The innermost ring, known as the halo, is shaped like a doughnut, and it extends down to about 20,000 miles above Jupiter’s clouds. Grains from the inner edge of the disk spiral down into Jupiter’s atmosphere, creating meteors. The next ring out is the main ring. It’s a lot flatter, but it also contains a lot more material, so it’s much denser. And outside that are two bands that together form the gossamer ring. The rings are held in position by the gravity of several small moons that orbit at or near the edges of the rings. In fact, the moons are the source of the rings. Big chunks of ice and rock occasionally slam into the moons. That blasts dust and bits of rock into space, where the particles enter the rings. This process continually supplies fresh material to the rings — and may have kept them going for billions of years. Jupiter stands near our own moon late tonight. It looks like a brilliant star close to the left of the Moon as they climb into view around midnight, and to the upper left of the Moon at first light. More about the Moon, Jupiter, and a bright star tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The Rosetta spacecraft snapped the Philae lander (left) shortly after it headed for a touchdown on Comet 67P/Churyumov-Gerasimenko on November 12. The lander itself took the image of the comet at right from a distance of about two miles (3 km). Philae is scheduled to spend the next several months probing its surroundings and watching the comet change as it nears the Sun. [ESA/Rosetta/Philae] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A “streaky” meteor shower will be at its best before dawn on Monday, November 17, according to the editors of StarDate magazine. Unfortunately, this won’t be one of its better years, as the partially illuminated Moon will wash out some of the meteors. Even so, the Leonid meteor shower should produce a “shooting star” every few minutes. read more

  • An artist's concept shows the Philae lander touching down on Comet 67P/Churyumov–Gerasimenko on November 12. The Rosetta spacecraft, which is orbiting the comet, released Philae early in the day, with touchdown coming seven hours later. The lander will spend several months riding along with the comet, measuring its composition and watching as gas and dust spew into space around it. [ESA/ATG Medialab] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • There’s a problem with Titan, the largest moon of Saturn. There’s a fair amount of methane in its atmosphere and in its big lakes. But under the sunlight, the methane shouldn’t last very long — only a few million years. That means that fresh methane is being added to the atmosphere, although scientists haven’t found the source. Titan is the second-largest moon in the solar system — bigger than the planet Mercury. It’s enveloped by an atmosphere that’s denser and colder than the air on Earth. The atmosphere contains a variety of hydrocarbons — mostly methane, with a bit of ethane, acetylene, and others. The ethane and methane form clouds and fill lakes around Titan’s poles. The problem, though, is that methane in the upper atmosphere gets destroyed by sunlight. This process is so efficient that it would take only a few million years to deplete all the methane in Titan’s atmosphere today. So there must be a source of fresh methane somewhere on the big moon. One possibility is volcanoes that emit super-cold liquids or gases instead of molten rock. There could be big deposits of methane ice below the surface that could feed into the volcanoes. The Cassini spacecraft has found hints of such volcanoes, but no confirmation. Astronomers are using telescopes on Earth to study how methane moves across Titan as the seasons change. That may yield some clues about the methane’s origin — helping to solve the problem with this intriguing world.   Script by Damond Benningfield, Copyright 2014   Today’s program was made possible by a grant from the NASA Science Mission Directorate. For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Sunlight glints off the surface of a large lake on the surface of Titan, the largest moon of Saturn, in this infrared view from the Cassini spacecraft. Titan is so cold that its lakes are filled with liquid ethane and methane. Clouds occasionally drift across them, perhaps fed by evaporation from the lakes themselves. [NASA/JPL/Univ. Arizona/Univ. Idaho] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

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