StarDate

StarDate

StarDate Online

  • For the most part, astronomers aren’t a superstitious lot. And they certainly don’t believe in ghosts. Yet it would be hard to blame them for getting a few chills on a lonely Halloween night, when the motors groan and the dome rattles in the blustery wind — especially when there are graves right outside the door — or even below the dome itself. Until well into the 1900s, it wasn’t uncommon for astronomers to be buried at their observatories. In part, that’s because many of the observatories were privately built and owned. So one of America’s first astronomers, David Rittenhouse, was buried beneath the observatory he built in Pennsylvania. That observatory has long since vanished. But several that are still around feature the graves of early astronomers or patrons. Percival Lowell, for example, is buried on the grounds of the observatory he founded in Flagstaff, Arizona. A crypt beneath Allegheny Observatory in Pittsburgh holds the ashes of some of its early astronomers and their family members. And James Lick, who founded the Lick Observatory in California, is buried in the base of the giant refracting telescope he provided for. So if you happen to be an astronomer who ventures into the dark dome on this autumn night, don’t worry about those odd little bumps and groans. They’re not the work of ghosts — it’s just Halloween.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The only spacecraft ever to orbit the planet Mercury has gotten especially close to it over the past few months — as close as 15 miles. It’s moving back away from the planet right now as it nears the end of its mission. Messenger was launched 10 years ago, and entered orbit around Mercury in 2011. During roughly 3,500 orbits, it’s clicked off more than a quarter of a million pictures of the solar system’s tiniest planet. They reveal impact craters, volcanic plains, and fault lines edged by cliffs that are miles high. Messenger has also mapped the mineral and chemical makeup of the surface, and it’s probed conditions inside the planet as well. It should produce an even better look at Mercury’s interior in its final months. Lowering its altitude will allow Messenger to map the planet’s gravitational and magnetic fields in much greater detail. Among other things, those observations will reveal more about Mercury’s core. The craft also will get a closer look at some of the more interesting features on Mercury, including deposits of ice at its poles. Messenger will end its mission next March, when it’ll slam into the planet it’s told us so much about. And Mercury is just peeking into view in the morning sky. It’s quite low in the east-southeast as twilight paints the sky, so you need a clear horizon to spot it. Although it looks like a bright star, it’s tough to find through the twilight. It’ll remain in view for a couple of weeks.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A bright, fresh impact crater gleams at the top left corner of this image of Mercury from the Messenger spacecraft, which has been orbiting the planet since 2011. Flight controllers briefly lowered its orbit to as close as 15 miles, which will allow scientists to map Mercury's gravitational field in greater detail. Messenger is expected to end its mission next spring. [NASA/JHUAPL] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Ten million years ago, some massive stars close to our own solar system blew themselves to bits. These exploding stars carved a big bubble in space and filled it with superhot gas. And today, our solar system is plowing through that bubble — a peanut-shaped region that’s about 300 light-years long. By earthly standards, the space between the stars is a hard vacuum — there’s just not much there. But there are a few atoms and molecules, known collectively as the interstellar medium. Shock waves from the exploding stars swept away most of the material around them. So the interstellar medium in this region, known as the Local Bubble, is especially thin — no more than a few percent as dense as the typical stretch of interstellar space. But it’s also especially hot, with its gas heated to a million degrees. As the bubble expands, it may squeeze denser clouds of gas and dust around it. Eventually, the clouds could break up into smaller clumps, which could collapse to form new stars. And those stars would be enriched by some of the material forged by the exploding stars — heavy elements like iron and nickle and even gold. Many of those heavier elements are key ingredients for planets like Earth. So cosmic destruction — the exploding stars that cleared out the Local Bubble — could someday lead to acts of creation — forging new worlds in the vastness of interstellar space. Tomorrow: getting close to a small world in our own solar system.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Measuring the distances to astronomical objects is hard work. But it’s critical for understanding the universe. Unless you know how far away an object is, you can’t know its brightness, its size, its gravity, or anything else about it. An example of just how tough the job is is the Pleiades star cluster — also known as the Seven Sisters. It climbs into good view in the east by around 10 p.m., and looks like a tiny dipper. Astronomers have been studying the Pleiades since the invention of the telescope. Even so, measuring its distance hasn’t been easy. The most accurate technique is called parallax. Astronomers look at the stars of the Pleiades when Earth is on opposite sides of the Sun. That produces a tiny shift in the position of the stars. The angle of the shift reveals their distance — about 430 light-years according to most studies. Recently, though, a team of astronomers used a network of radio telescopes to make new measurements. The network produces images that are unusually sharp, helping overcome the blurring effects of Earth’s atmosphere. Those measurements place the Pleiades a bit farther than the accepted value — about 443 light-years. That difference isn’t very big — or, for most things, very significant. Yet the fact that astronomers keep measuring the distance to this prominent star cluster shows just how important it is to get it right, and find a definitive distance to the Seven Sisters.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Like a runner on a treadmill, Mars is moving quickly just to stay in place right now. The planet is sliding against the background of stars at about the same rate at which that background is moving from night to night. As a result, Mars will appear at almost exactly the same point in the evening sky for the next several weeks. As Earth orbits the Sun, the stars in the night sky shift westward, so they rise and set four minutes earlier each night. And most of the time, the planets move eastward against that background, which is just what Mars is doing right now. And it’s doing so at a rate that just about matches the shift in the background. The combination means that Mars will stay at basically the same position in the sky for a while. Right now, for example, it’s low in the southwest at about 7:30 p.m. And a month from now, once you account for the end of Daylight Saving Time, it’ll stand in almost that same spot at the same time of evening. The planet will begin to shift up and to the west a bit in December, then finally drop from sight as it passes behind the Sun in early spring. And Mars has a prominent companion the next couple of evenings: the crescent Moon. Mars is to the left of the Moon tonight, and will stand about the same distance to its lower right tomorrow night. The little planet looks like a bright yellow-orange star — an unmoving beacon set against the distant stars. Tomorrow: the Seven Sisters move farther away.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The star system known as Capella is a rarity — it contains two giant stars that are nearly identical. But the stars might not have been born so much alike. It’s possible that one of them dumped some of its gas on the other, equalizing the system. Capella is the leading light of Auriga, the charioteer. It’s in good view in the northeast by mid-evening — one of the brightest stars in the night sky. Both of its giant stars are nearing the ends of their lives, so they’ve gotten bloated. Both are about two-and-a-half times as massive as the Sun, several times the Sun’s diameter, and dozens of times its brightness. They orbit each other at about three-quarters of the distance from Earth to the Sun. But some quirks in the system indicate that things weren’t always so equal. As an example, the more massive star is locked so that the same side always faces its companion, but the companion spins much faster. That could mean that the stars were more unequal when they were born. The more-massive star evolved faster, and entered the giant phase of life before the other. As it puffed up, it began dumping gas onto the surface of its companion. That would have slowed down the heavier star while speeding up the companion. Today, both stars are evolving in a hurry. Their sizes will vary greatly over the next few million years. That could mean that they’ll exchange gas again in the future — altering the evolution of both of these bright giants.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A postcard depicts the Elgin Watch Company Observatory in Elgin, Illinois. The observatory's telescopes used the stars to accurately record the time, which was fed to the adjacent watch factory. Elgin used the observatory as part of its national advertising campaign. Although the company and factory are gone, the observatory is still standing. Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Capella is one of the brightest beacons in the night sky. The yellow-orange star is in good view in the northeast by mid-evening, and stands high overhead a couple of hours before dawn. It’s the sixth-brightest star system in all the night sky, so it’s hard to miss. Because of its brilliance, Capella served as a navigational beacon for the seafarers of ancient Polynesia, where it was known as “the canoe bailer of Makali’i.” Along with several other bright stars, it guided sailors across hundreds of miles of open ocean with pinpoint accuracy. Capella also played a key role in ancient Greece — not as a guiding light, but as a bit of mythology. The star represented a goat that nursed the young Zeus, the king of the gods. Later, the goat’s horn broke off, so Zeus transformed it into a cornucopia — a “horn of plenty” that provided unending food and drink. Originally, Capella was its own constellation — a single star representing the goat. But a couple of thousand years ago, it was merged with the next-door constellation Auriga, the charioteer. So today, it’s still a goat, but it’s sitting on the shoulder of the charioteer. Although Capella looks like a single pinpoint of light, it’s actually a system of at least four stars. Two of them are red dwarfs — cosmic embers too faint to see with the eye alone. What we see as Capella consists of two stellar giants — stars in the final stage of life. We’ll have more about that pair tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A half-century ago, the North Star had a little hiccup. Today, astronomers are still trying to understand what happened. Polaris is a stellar supergiant that’s nearing the end of its life. The nuclear “engine” in its core is changing the way it produces energy. And that’s made the star unstable. Its outer layers pulse in and out like a beating heart, with each “beat” taking about four days. Until 1963, Polaris’s brightness varied by about 10 percent with each beat. And the pulses were getting longer — by about four seconds per year. From 1963 to ’66, though, things changed. The change in brightness with each beat dropped, and the length of a beat began to grow shorter. After that, the pulses began getting longer again, at about the same rate as before the glitch. But the variation in brightness remained small. Just what caused the change is uncertain. One possibility is that the star’s average diameter shrank by less than one-tenth of a percent. Another is that the star swallowed a massive planet. Astronomers continue to monitor the changes in Polaris, helping them better understand the final stages of life for such giant stars. Look for Polaris due north every night of the year. It’s not all that bright, but there’s an easy trick for finding it. Line up the stars at the outer edge of the bowl of the Big Dipper. Then follow that line up and away from the bowl until you come to the first moderately bright star — the unsteady North Star.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Astronomers have been keeping a close eye on the North Star, Polaris, for centuries. That’s allowed them to compile an impressive dossier. They know that the system actually consists of several stars, for example — a brilliant one that’s visible to the eye alone, plus some fainter companions. They know that the bright star is a supergiant that’s much bigger and heavier than the Sun. And they know that it pulses in and out like a beating heart. Even so, there are a lot of open questions about Polaris. One of the most important is its distance. The most direct method for measuring a star’s distance is parallax. Astronomers look at the star when Earth is on opposite sides of the Sun. That lets them see the star shift back and forth a tiny bit against the background of more-distant stars. The size of that shift reveals the star’s distance — in this case, about 430 light-years. Astronomers use other techniques to measure distances as well, and those don’t all agree with the parallax distance. One technique makes detailed measurements of the individual wavelengths of the star’s light and compares them to models of how stars behave. Using that technique, a study a couple of years ago came up with a distance of just 325 light-years. Most astronomers go with the parallax measurement. Even so, there’s still a bit of wiggle room in measuring the distance to the North Star. We’ll talk about another mystery of the North Star tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The afternoon sky will get a little darker than normal for most of the United States tomorrow. That’s because there’s a partial solar eclipse. A solar eclipse occurs when the new Moon passes directly between Earth and the Sun. Most months, the Moon skims just above or below the Sun as seen from Earth, so there’s no eclipse at all. This eclipse is only partial — the Moon will cover only a portion of the Sun’s disk. So the sky will resemble an early dusk, and the temperature may drop a little bit. The eclipse begins when the Moon’s shadow first touches Earth, over Siberia, around 2:30 p.m. Central Time. The shadow then spreads to the southeast, crossing Alaska, Canada, then the Lower 48 states. The eclipse will be deeper from points farther north and west. From Anchorage, for example, the Moon will cover more than half of the Sun’s disk at the point of greatest eclipse. Only a third of the Sun will be eclipsed from Los Angeles and Dallas, though, and only a tiny notch will be missing as seen from New York and Miami. In fact, for those in the eastern third of the country, the eclipse will still be in progress at sunset. Keep in mind that it’s not safe to look at the eclipse directly — the Sun is still bright enough to damage your eyes. Instead, look through dark welder’s glass. You can also track the eclipse by looking at the ground under a leafy tree, where the gaps in the leaves create neat little pictures of this celestial lineup.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • The afternoon sky will get a little darker than normal for most of the United States Thursday. That’s because there’s a partial solar eclipse, according to the editors of StarDate magazine. read more

  • The stars move across the sky with clockwork precision. So perhaps it’s not surprising that a company that made timepieces took advantage of the stars — to improve both its watches and its image. The Elgin National Watch Company was established in Illinois in 1864 — 150 years ago — and it quickly became one of the world’s leading watchmakers. And in 1910, it built its own astronomical observatory to track the time. The observatory used a transit telescope, which measured the precise time that bright stars crossed the meridian — the line across the sky that passes from due north to due south. Comparing those times with astronomical almanacs revealed the precise time at the company’s factory. That time was kept by a set of high-precision German clocks, which were sealed inside a climate-controlled room. This method was accurate to within a tenth of a second. Time signals were transmitted to the factory to allow workers to precisely set new watches. Elgin built its entire image around the observatory. The company’s ads featured pictures of it, and encouraged readers to “Go to the Stars for the Time.” After World War II, though, atomic clocks began providing more accurate time, and less-expensive brands pushed Elgin watches aside. The company donated the observatory to the local schools in 1960, and it still stands today. The company, alas, does not. It shut its doors and sold off its name in 1968.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Upsilon Andromedae might not dazzle the eye, but one fact really makes it sparkle: It’s one of the brightest stars in the night sky known to have four or more planets. The star is bigger, brighter, and heavier than the Sun. It has a distant companion star that’s a faint cosmic ember. The two stars are known as Upsilon Andromedae A and B. The planets orbit star A, so they’re known as Upsilon Andromedae A-b, A-c, A-d, and A-e. That’s a neat system for the astronomers who study planets in other star systems — it helps them know just where everything is. For the rest of us, though, the system’s a bit dull. Such names have none of the appeal of Vulcan, Gallifrey, Arrakis, or many other planet names from science fiction. But that’s about to change. The International Astronomical Union is holding a contest to name more than 300 exoplanets, including those of Upsilon Andromedae. Over the next few months, it’ll accept proposals for exoplanet names from astronomy-related groups, such as planetariums and museums. It’ll pick the best proposals next spring, and allow the general public to vote on the names. It’ll formally adopt the new names next summer — adding a little character to some distant worlds. Upsilon Andromedae is about a third of the way up the east-northeast sky at nightfall, and stands directly overhead in the wee hours of the morning. Although it’s visible to the unaided eye, you’ll need a starchart to pick it out.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • A thin but reliable meteor shower is at its best the next couple of nights. The view is best in the wee hours of the morning, when you might see a dozen or two “shooting stars” per hour. The Orionids occur when Earth sweeps through the orbital path of Comet Halley, which has been making periodic trips through the inner solar system for more than two millennia. It sheds bits of dusty debris on each trip, which spread out along the comet’s path. These particles zip into Earth’s upper atmosphere at speeds of up to 140,000 miles an hour. They quickly vaporize, forming the glowing streaks known as meteors. Although the shower probably has been around for centuries, no one took formal note of it until 175 years ago. Edward Herrick of Yale College recorded a clump of meteors in October of 1839. He confirmed the activity the following year. Herrick didn’t find the shower’s peak, though — the period of a few hours with the greatest number of meteors. That was left to Alexander Herschel, who made the discovery 150 years ago, in 1864. The intensity of the Orionids waxes and wanes over the years. That’s because the meteor stream is clumpy. If we happen to pass through a denser clump of comet dust, we see more meteors. This isn’t expected to be one of those years. Even so, there’s not much moonlight to interfere with the fireworks. So if you have dark, clear skies in the hours before dawn the next few mornings, keep an eye out for the Orionid meteor shower.   Script by Damond Benningfield, Copyright 2014   For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Mars is low in the southwest as night falls. It looks like a fairly bright orange star. And if you have strong binoculars or a telescope, you might make out a fuzzy companion quite close to the planet the next few evenings. Comet Siding Spring will be just to the left of Mars tonight, and closer to the right of Mars tomorrow night. The comet could create a brief but intense meteor shower on Mars tomorrow, as a barrage of dust grains slams into the planet’s upper atmosphere. Debris from a different comet will strafe Earth over the next few nights, spawning our own meteor shower. It’s not a great one, but there’s not much moonlight around to interfere with the fireworks, so it’s worth a look. The Orionid shower is created by Comet Halley. The comet hasn’t visited the inner solar system in a quarter of a century. But as it orbits the Sun, it sheds small bits of rocky debris. These grains of dust spread out along Halley’s orbital path. Earth flies through this path every October, so some of the grains slam into the atmosphere at tens of thousands of miles per hour. They quickly vaporize, forming the glowing streaks of light known as meteors or shooting stars. The Orionids should be at their best tomorrow and Monday nights, although you might see a few outliers tonight as well. The shower is best viewed in the wee hours of the morning, as your part of Earth turns most directly into the meteor stream — a strafing run from a distant comet.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Mars is about to dodge a big snowball — a comet that will swing just 82,000 miles above the planet’s surface on Sunday, according to the editors of StarDate magazine. That’s just a third of the distance between Earth and the Moon, so it’s quite a close call. Comet Siding Spring will not be visible from Earth with the unaided eye, but it will be a spectacular sight under the dark Martian sky. It could even spawn a short but brilliant meteor shower caused by the dust grains plunging into the Martian atmosphere. read more

  • The fleet of Mars-orbiting spacecraft will hide behind the Red Planet on Sunday morning. They’ll be trying to avoid a possible bombardment by tiny cosmic missiles — grains of dust from a comet. Although many of those grains are no bigger than a BB, they’ll be moving at about 125,000 miles an hour — fast enough to damage or even destroy a spacecraft. Comet Siding Spring will pass about 82,000 miles from Mars early Sunday — only a third of the distance from Earth to the Moon. That should create quite a show in the Martian sky — not just the view of the comet itself, but a possible meteor shower caused by the dust grains plunging into the Martian atmosphere. The atmosphere will protect rovers on the surface of Mars. But orbiters are vulnerable to the dust grains. So navigators have tweaked their orbits to keep the craft on the other side of Mars at the time of the greatest threat. Before and after that, however, the orbiters will keep a close eye on the show. They’ll study the comet itself, which is a small chunk of ice and rock. They’ll also study the cloud of gas and dust around the comet, as well as its long tail. And they’ll measure how the gas and dust interact with the Martian atmosphere — after Siding Spring has passed safely by. We’ll talk about a meteor shower here on Earth tomorrow.   Script by Damond Benningfield, Copyright 2014 For more skywatching tips, astronomy news, and much more, read StarDate magazine.

  • Comet Siding Spring will pass about 85,000 miles above Mars on October 19, as depicted in this artist's concept. Several Mars orbiting spacecraft will "hide" behind Mars to protect themselves from possible cometary debris. The orbiters, as well as two rovers on the surface, will study the comet before and after its close encounter with Mars. [NASA/JPL] Text ©2014 The University of Texas at Austin McDonald ObservatoryFor more skywatching tips, astronomy news, and much more, read StarDate magazine.

Valid XHTML & CSS | Template Design LernVid.com and ah-68