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  • This Hubble Space Telescope view of NGC 7714 shows the aftermath of a galactic fender-bender. The spiral galaxy side-swiped another (which is out of view), pulling out great streamers of stars (the yellow-orange swirls) and triggering the birth of millions of new stars, which form bright blue strands. Many of the newly born stars are much more massive than the Sun, so they quickly lose much of their material through strong winds. The galaxy is about 100 million light-years away. [ESA/NASA/A. Gal-Yam (Weizmann Institute of Science]

    Text ©2015 The University of Texas at Austin McDonald Observatory

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The Moon passes through the middle of one of the largest “asterisms” in the sky the next couple of nights: the Winter Circle. It contains several of the night sky’s brightest stars. But it’s so spread out that it’s hard to take in all at once.

    An asterism is a pattern of stars that forms a distinctive shape or picture. It can be within a single constellation, or it can cross over constellation boundaries. The Winter Circle is in the latter category — it encompasses stars in six constellations. It spans about five times the width of your open hand held at arm’s length.

    Tonight, the circle’s hub is close to the lower right of the Moon: Betelgeuse, the orange shoulder of Orion, the hunter. Orion’s other brilliant star, Rigel, forms part of the circle itself. It’s to the lower right of Betelgeuse.

    If you go clockwise from there, down at the six o’clock position you’ll come to the Dog Star Sirius, the brightest star in all the night sky. Next up is Procyon, the little dog star, then Pollux and Castor, the twins of Gemini.

    The circle sweeps upward from there to bright yellow-orange Capella, in Auriga, the charioteer, and then over to Aldebaran, the eye of Taurus, the bull. Finally, it’s back down to Rigel to complete the circle.

    It’s one of the grandest pictures in the night sky — a circle of bright stars that tonight forms a giant ring around the bright gibbous Moon.

    Tomorrow: projecting Earth’s equator into the night sky.

     

    Script by Damond Benningfield, Copyright 2014


    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Several weak meteor showers rain into the night sky at this time of year — showers with names like the Alpha Corona Borealids and the February Eta Draconids. They’re all puny, but they add up. Under dark skies, you can expect to see a handful of meteors just about any night of the year.

    Astronomers have identified almost 600 possible meteor showers. Only a few produce enough “shooting stars” to make them worth mentioning. But even if they don’t have aesthetic value, they all have scientific value. Every meteor shower is produced by a trail of debris from a comet or asteroid. Plotting the courses of the meteors can help astronomers track down these parent bodies.

    A couple of years ago, in fact, researchers at Cal Poly Pomona used a network of 60 video cameras to photograph thousands of meteors in January and February skies. Their goal was to see if any of the meteor streams might suggest that their parent bodies were on a collision course with Earth.

    The observations detected meteors associated with 42 showers, including 16 that had never been seen before. Only one of the showers was tied to a parent object, though, and it’s no danger to Earth. But the technique can help point the way to more parent bodies — including those that might someday threaten our planet.

    Even on a night with a lot of moonlight, like tonight, if you can get away from city lights you might still see a few bright meteors blazing across the night sky.

     

    Script by Damond Benningfield, Copyright 2014


    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • This image, snapped by the Dawn spacecraft on January 25, 2015, is the sharpest yet of Ceres, the largest asteroid. Taken from a range of 147,000 miles (237,000 km), the image shows more detail than even the best taken by Hubble Space Telescope. Dawn will draw closer to Ceres over the next few weeks and enter orbit around the little dwarf planet on March 6. [NASA/JPL/UCLA/MPS/DLR/IDA]

    Text ©2015 The University of Texas at Austin McDonald Observatory

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • In a cavern a half-mile below the hills of northern Minnesota, scientists and engineers have built a “battleship in a bottle” — a 6,000-ton concoction of steel and electronics designed to study some of the most ephemeral particles in the universe.

    Neutrinos are produced in nuclear reactions, such as those that power the Sun and other stars. They stream through space at almost the speed of light, and zip through stars and planets without stopping. In fact, trillions of them pass through your body every second.

    Early theories said that neutrinos shouldn’t have any mass. But experiments found that they come in three varieties, known as flavors. And they can change flavors as they speed along — like a scoop of ice cream morphing from chocolate to vanilla to strawberry. For this idea to be correct, neutrinos must have a small mass, with a different mass for each flavor.

    The Minnesota experiment, known as MINOS, is studying how the neutrinos change as they speed through the universe. Scientists fire a beam of one flavor of neutrinos from a lab in Illinois. The beam travels hundreds of miles below Wisconsin and Lake Superior before some of its neutrinos hit the detector. There are so many neutrinos that one of them occasionally zaps an atom in the detector, causing a splash of atomic particles.

    Studying these events should help scientists learn how neutrinos work — information that can help them better understand the reactions that power the stars.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • To catch the whisper of a passing particle of dark matter, two experiments in northern Minnesota get cold. One of them, in fact, is chilled to a few thousandths of a degree above absolute zero.

    Dark matter appears to make up about five-sixths of all the matter in the universe. Astronomers see it on large scales because it exerts a strong gravitational pull on the normal matter around it.

    Yet no one has ever seen an individual bit of dark matter. It rarely interacts with normal matter in any way — and it may not interact at all.

    The experiments in Minnesota use detectors made of germanium. If a particle of dark matter rams into the nucleus of a germanium atom, the nucleus should “wiggle” a bit, producing a tiny amount of heat and a tiny change in electric charge.

    But the detectors need an enormous amount of shielding. They’re in a laboratory that’s a half-mile below ground; the layers of rock screen out cosmic rays, which can zap the germanium atoms.

    At normal temperatures, the atoms vibrate so much that they would overwhelm any signal from a collision with a particle of dark matter. So the detectors in the Cryogenic Dark Matter Survey are chilled to almost absolute zero by a complicated refrigeration system.

    Even so, the experiment hasn’t turned up any evidence of dark matter. But scientists are planning to build a bigger version of the experiment in a deeper mine — changes that could help catch the faint signal of dark matter.

     

    Script by Damond Benningfield, Copyright 2014


    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Scientists look for the most elusive particles in the universe in underground laboratories, such as this one adjacent to an old iron mine in northern Minnesota. The Soudan Laboratory is studying neutrinos with the hexagonal detector at left, which is more than two stories tall. A mural depicts the effort to solve some of the most important mysteries in physics. Detectors in an adjacent cavern are searching for particles of dark matter, which makes up about five-sixths of all matter.

    Text ©2015 The University of Texas at Austin McDonald Observatory

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A half-mile below the hills of northern Minnesota, visitors to the Soudan Mine State Park face a choice. Turn left, and they can climb aboard carts like those in “Temple of Doom” to explore an abandoned iron mine. Turn right, though, and they enter a laboratorywhere scientists are studying some of the most important topics in modern physics.

    Miners began hauling out iron ore in the 1880s. The mine was shut down in 1962, and it’s been a state park ever since.

    In recent decades, though, scientists dug two new tunnels off the mine’s lowest level. One of the tunnels hosts an experiment that studies neutrinos — phantom-like particles produced in the hearts of stars. The other hosts two experiments that are trying to find particles of dark matter — matter that produces no detectable energy, but that exerts a gravitational pull on the normal matter around it.

    Several dark matter experiments are operating around the world, and all of them are deep underground. That’s because interactions between dark matter and normal matter are extremely rare, if they happen at all. At the surface, the signal of such an interaction would be drowned out by cosmic rays — heavy particles from deep space — as well as the radioactive decay of elements on Earth’s surface and other events.

    The rock above the Soudan laboratory blocks most of these other signals. That should make it easier to detect the “fingerprint” of dark matter. More about that tomorrow.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • As befits his status as a hero, Perseus strides boldly across the sky this evening. He’s high overhead at nightfall, crowning the sky with a couple of streamers of moderately bright stars.

    Perseus rescued the princess Andromeda from a nasty sea monster. In one version of the story, he turned the monster to stone by showing him the head of Medusa, one of the Gorgons — monsters in their own right.

    The names of four of the constellation’s stars are tied to that story. Collectively, they’re known as Gorgonea — the Gorgons. And the most impressive of the four is quite the monster.

    Gorgonea Tertia — the third Gorgon — is entering the final stage of its life. It converted the original hydrogen fuel in its core to helium, then converted the helium to carbon and oxygen. The core isn’t hot enough to continue the process, though, so it’s no longer generating nuclear reactions. But it is hot enough to push on the layers of gas around it, making the star puff up to enormous proportions.

    Right now, Gorgonea Tertia is roughly 150 times wider than the Sun. In the near future — on the stellar timescale — the star will get even bigger and brighter. Soon after that, it’ll eject its outer layers, creating a colorful bubble. But the bubble will quickly expand so much that it’ll fade from view, leaving only the star’s hot but dead core — a timid end for a monstrous star.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • One “dog” star leads another across the sky on winter nights. Procyon, the little dog, precedes the Dog Star, Sirius. They’re in good view in the eastern sky by a couple of hours after sunset.

    Sirius is the brightest star in the night sky, so it’s easy to find. Procyon is off to its upper left. It’s not quite as bright, but it’s still one of the brighter stars around, so you shouldn’t have any trouble picking it out.

    The name Procyon means “before the dog.” It indicates that from middle-northern latitudes and above — say, anywhere northward of about Dallas — Procyon rises a little before Sirius. In cultures where Sirius played a prominent role in religious and public life, the first appearance of Procyon in the dawn sky was an alarm clock — it alerted people to the return of Sirius a few days later.

    Procyon itself closely resembles its brighter canine cousin. Both stars are bigger, brighter, and heavier than the Sun. But Procyon’s a little farther away — about 11.5 light-years, versus 8.6 for Sirius — so it doesn’t look quite as bright.

    Also like Sirius, Procyon has a “dead” companion known as a white dwarf. It’s the core of a star that was once bigger and brighter than Procyon itself. It used up all the nuclear fuel in its core, though, so the core stopped producing energy. The star’s outer layers then streamed off into space, leaving only the dead core — a cosmic ember that trots along with the little dog star.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Asteroids are always getting in the way. Every night, several of them pass in front of stars, briefly blocking the stars from view. Astronomers don’t mind, though. In fact, each of these occultations offers a chance to learn about the asteroids themselves.

    Occultations are visible across a narrow path — usually just a few miles wide. To be of greatest value, that path needs to cross over several telescopes. They don’t have to be at major observatories, though — many amateur astronomers contribute valuable measurements as well.

    By comparing the length of an occultation at different sites along the path, and adding observations close to the path that show no occultation, astronomers can learn quite a bit.

    A couple of years ago, for example, telescopes across the United States watched an occultation of two asteroids that form a binary. Several telescopes saw the occultation, while the rest saw nothing. From those observations, astronomers measured the size and shape of both asteroids with an accuracy of a few miles.

    A few months earlier, an occultation by an asteroid named Chariklo revealed that it was encircled by rings — the only rings yet seen around any asteroid. Observations of later occultations showed that there are four rings, which form two close pairs. A small moon could orbit outside the rings, with an even smaller one between them. Future observations may confirm them — when Chariklo gets in the way of another star.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A brilliant aurora blazes high in Earth's atmosphere in this photo from the International Space Station. An aurora forms when charged particles from the Sun run into Earth's magnetic field, which funnels them toward the surface, where they strike atoms and molecules of nitrogen and oxygen, causing them to glow. Although Venus generates no magnetic field, researchers have found that it may also produce aurorae under special conditions. [NASA]

    Text ©2015 The University of Texas at Austin McDonald Observatory

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A thousand or so large asteroids follow orbits that bring them close to Earth. And once every million years or so, one of these big space rocks rams into our planet, causing widespread devastation.

    Big asteroids threaten Mars as well. In fact, Mars is much closer to the inner edge of the asteroid belt, so there are more big rocks whose orbits bring them close to Mars than to Earth. But Mars is smaller than Earth is, and its gravitational pull is weaker, so it doesn’t drag in as many asteroids.

    A recent study suggested that Mars also gets hit by one of these large asteroids — roughly two-thirds of a mile across or bigger — once every million years or so.

    The study also suggested that Mars is about three times as likely to get hit when it’s farthest from the Sun than when it’s closest. Mars’s orbit is a good bit more lopsided than Earth’s, so the planet’s distance from the Sun varies by almost 30 million miles. The closer proximity to the asteroid belt when Mars is farthest from the Sun should account for some of the higher risk of impact, but not all.

    Far from the Sun or close in, though, it seems likely that Mars is a common target for big asteroids.

    And Mars is easy to pick out this evening because it’s quite close to the crescent Moon. It looks like a moderately bright yellow-orange star quite close to the left of the Moon. The much brighter planet Venus, the brilliant “evening star,” stands below them.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • One of the most spectacular sights in the night sky is an aurora — a shimmering curtain of light. It’s produced by the interaction between Earth’s magnetic field and the solar wind — a stream of charged particles from the Sun. The magnetic field funnels the particles toward the surface, where they hit atoms and molecules, making them glow.

    Aurorae have been seen on other worlds as well. And they may have been seen on one where they weren’t expected: Venus.

    Unlike Earth and the other worlds with confirmed aurorae, Venus doesn’t generate a magnetic field. No magnetic field, no aurora.

    But observations by a telescope in New Mexico, and a spacecraft in orbit around Venus, suggest otherwise. The ground-based telescope has seen a green glow on Venus’s nightside. And the spacecraft detected energy at similar wavelengths.

    Researchers at New Mexico State say the glow is most likely an aurora caused by solar wind particles hitting oxygen atoms about 75 miles above the surface.

    The glow may require a perfect set of conditions: the unique chemistry of Venus’s atmosphere combined with a big outburst of particles from the Sun. The particles flow around Venus, forming a turbulent patch behind the planet. Particles in this patch are forced down into the atmosphere — where they just might create a bright glow high above the planet.

    And Venus shines brightly as the “evening star” right now. Tonight, it stands just to the left of the crescent Moon.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Earth and the Moon are sometimes called a binary planet, because they’re the most evenly matched pairing of a major planet and a moon in the solar system — the Moon is more than a quarter of Earth’s diameter.

    The list of thousands of planets discovered in other star systems doesn’t include any true binaries — pairs of planets with similar sizes. But recent research suggests that such systems aren’t impossible — just highly improbable. They’d require a set of circumstances that would be tough to produce. In fact, they’d have to be similar to those that gave birth to the Moon.

    The leading theory says the young Earth was hit by another planet-sized body. The collision spun off a ring of debris that coalesced to form the Moon.

    Researchers at Caltech found that to make a true binary, you need a “kissing” encounter between two similar-sized planets. The two would need to pass extremely close to each other — perhaps close enough to touch — at low speeds. In such an encounter, the gravity of each planet would distort the other, changing their orbital momentum. The two worlds would loop around each other several times, creating distortions on each close approach. Over time, they’d settle into a stable orbit around each other — creating a binary planet.

    Such a system could be found if it passed in front of its parent star, blocking some of its light. The way the brightness changes would reveal the presence of two planets orbiting as one.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Our universe probably holds a hundred billion galaxies. And each galaxy contains anywhere from a few million stars to a trillion or more. Add it all up and that’s a whole lot of zeroes in the number of stars.

    Yet that may be only half of the story. According to recent observations by a small space telescope, there may be as many stars between galaxies as in them.

    A project known as CIBER launched a small infrared telescope several times. Each flight lasted just a few minutes, but the total time above the atmosphere allowed the telescope to measure much of the infrared light in the universe. Astronomers masked out the glow of galaxies, plus the infrared background of our own galaxy, the Milky Way.

    When they ran the numbers, the astronomers found that a lot of infrared light was unaccounted for. This glow was spread fairly evenly across the sky.

    According to the project scientists, the most likely explanation is that there are a lot of stars between the galaxies. The stars didn’t form out in these voids. Instead, they were stripped from their parent galaxies by interactions between galaxies. When galaxies get close to each other, the gravity of one can pull great streamers of stars from the other. Over time, the stars spread out, so they’re distributed fairly evenly between galaxies.

    That may mean that there’s not a sharp “edge” to any galaxy. Instead, they all taper off as some of their stars spread into the intergalactic void.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • When spring arrives in a couple of months, the Sun will stand near the body of one of the fish of Pisces. Over time, though, the Sun’s location at the vernal equinox slips westward. About 6500 years ago, it was just above the head of Orion, the hunter.

    Orion is best known for his strong shoulders and legs and his sparkling belt. The tiny triangle of stars that marks his head doesn’t look nearly as impressive. Yet the stars themselves really are standouts.

    The brightest of the three is known as Lambda Orionis. It’s actually a pair of stars locked in a tight orbit. Both stars are many times bigger, hotter, and brighter than the Sun. In fact, one of them is a member of the hottest class of stars. It’s tens of thousands of degrees hotter than the Sun, and more than 60,000 times brighter. That makes it easily visible across more than a thousand light-years of space.

    The other stars are Phi-1 and Phi-2 Orionis, which represent the hunter’s cheeks. Although they share a name, they aren’t related — they’re hundreds of light years apart. But both are much more impressive than the Sun.

    The hunter is well up in the southeastern sky at nightfall. Look for his belt — a short line of three bright stars — extending almost straight up from the horizon, with the bright orange star Betelgeuse to its upper left. The faint triangle that makes up Orion’s head is to the upper right of Betelgeuse.

     

    Script by Damond Benningfield, Copyright 2010, 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A group of hot young stars blazes in the constellation Orion, which is in the southeast this evening. The stars are in the Orion Nebula, a fuzzy blob of light to the lower right of Orion’s Belt. In fact, they help make the nebula shine.

    The nebula is a gigantic cloud of gas and dust — a nursery that’s given birth to thousands of stars. Four of those stars are called the Trapezium, because they form the shape of a trapeze. Each of the stars is less than a million years old. That’s a lot of years by human standards, but the blink of an eye for stars.

    The Trapezium’s stars are much hotter and brighter than the Sun. That’s because they’re also much more massive than the Sun. Such heavy stars burn through the nuclear fuel in their cores at a fantastic rate, which makes them shine brilliantly.

    Like the nebula itself, the stars of the Trapezium are about 1500 light-years away. The brightest member of the quartet is just visible to the unaided eye, but you’ll need binoculars to see the others.

    If not for the Trapezium, we wouldn’t see the Orion Nebula at all. The stars produce a lot of ultraviolet energy, which is absorbed by the nebula’s gas. This boosts the energy level of the atoms that make up the gas. When the atoms return to their normal energy level, they emit light — making the Orion Nebula shine brightly.

    Look for the Nebula — and the Trapezium — inside Orion. It’s in the east-southeast at nightfall, and arcs across the south later on.

     

    Script by Damond Benningfield, Copyright 2014

    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The Moon has a couple of bright companions at dawn tomorrow. Antares, the brightest star of Scorpius, stands to the right of the Moon. And slightly brighter Saturn, the second-largest planet in the solar system, is a little farther to the upper right of the Moon.

    The Moon itself is a thin crescent right now. It’s about to pass between Earth and the Sun, so it’s daytime across most of the far side of the Moon, and nighttime across most of the near side.

    If you were standing on the lunar nearside right now, its sky would be dominated by the bright gibbous Earth. Our planet is about to line up opposite the Sun as seen from the Moon, so it’s almost full.

    And it would be an impressive sight. Earth is almost four times the Moon’s diameter, so it covers a much larger area than the Moon does as seen from Earth. Earth’s surface is much more reflective than the surface of the Moon, too; combined with its greater size, that makes a full Earth roughly 50 times brighter than a full Moon.

    And since the same lunar hemisphere always faces our way, Earth stays in almost exactly the same spot in the sky as seen from any given location on the Moon, so you wouldn’t see Earth rise and set. You would see it go through an endless cycle of phases, though, from new to full and back to new. You’d also see our planet turn on its axis, and you’d see the patterns of clouds morphing from day to day — the ebb and flow of our constantly changing planet.

     

    Script by Damond Benningfield, Copyright 2014


    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The largest known reservoir of hydrocarbons isn’t in Texas, the oil sands of Alberta, or even the Persian Gulf. It sits on the surface of Titan, the largest moon of Saturn.

    The regions around Titan’s poles are speckled with lakes and seas. The largest are bigger than some of the Great Lakes. But Titan is so cold that water is frozen as hard as granite. So instead, the lakes and seas are filled with methane and ethane — liquid hydrocarbons — compounds that are similar to those that make up petroleum and natural gas.

    The Cassini spacecraft has used radar to probe deep into a few of the lakes and seas. It’s recorded depths of up to several hundred feet.

    That’s allowed scientists to calculate the volume of Ligeia Mare, one of the largest seas. It contains about three times as much liquid as Lake Michigan — and about 55 times as much liquid hydrocarbons as all the known oil deposits on Earth.

    The sea with the greatest surface area is Kraken Mare. Cassini measured the depth of a narrow inlet at about a hundred feet. But it couldn’t see the bottom of most of Kraken. That could mean that it’s deeper than Cassini’s radar can probe — more than 600 feet. If so, then Kraken would contain even more hydrocarbons than Ligeia.

    Saturn is in good view at dawn tomorrow. It looks like a bright star just a degree or so from the Moon. Titan is visible through a small telescope — a tiny dot near Saturn that’s the solar system’s biggest gas station.

     

    Script by Damond Benningfield, Copyright 2014


    For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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