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Astronomy From Your Back Yard - 12/15 to 12/21 2010

Backyard Astronomy Extra - Total Lunar Eclipse!

By Dave Grosvold

On Saturday evening, look just to the left of the Moon a mere 2° for the delicate Pleiades star cluster. The Pleiades is a beautiful, fairly tight open cluster in Taurus that was used by Native American tribes to test the eyesight of their scouts. See if you can see more than 5 stars in the Pleiades with the naked eye. If so, then you would have qualified as a scout in the Old West. This week, you may need to use binoculars to see the Pleiades due to the overwhelming glare of the waxing gibbous Moon.

Below the Pleiades by about a fist-width is orange Aldebaran. Aldebaran is part of the Hyades star cluster, an open star cluster in Taurus that looks to most like a small “V” laying on its side in the eastern sky. Far off to the left of the Hyades shines brighter yellow Capella. On Sunday evening, the Moon is to the left of the Hyades, and just to the left of a small star named Tau Tauri (τ Tau). By Monday evening, the Moon has moved just to the left of Zeta Tauri (ζ Tau.) By now, you've realized that the Moon has taken three nights to pass from one end of Taurus to the other.

   Click image for larger view
But the REAL highlight of the week is still yet to come. On Tuesday morning, the Full Moon occurs right at the mid-point of a total lunar eclipse! Make plans now to see this last lunar eclipse of the year. The eclipse begins just after midnight in the early-morning hours of Tuesday, December 21, 2010.

The eclipse reaches its mid-point at about 2:17 AM CST Tuesday morning. The Moon will be shining brightly very high in the early-morning sky during the eclipse, in the south-southeast. By the time it reaches mid-eclipse, the Moon will be high in the southwest, and will drop into the western sky by the end of the eclipse at 4:01 AM. The best way to view this eclipse is with a pair of binoculars or a small telescope.

The dim Little Dipper (Ursa Minor) hangs just about straight down from the North Star by about 9:30 PM all this week, as if it was hung from a hook on the wall of the sky. The brighter Big Dipper (Ursa Major) is rearing upward on its handle low in the north-northeast. You can easily find Polaris, (or the North Star,) by using the two end stars of the bowl of the Big Dipper.

Venus shines with a brilliant light in the southeastern sky this week before and during dawn. Venus now rises about two hours before the first light of dawn (about 3:45 AM CST,) and rises to an altitude of about 33° before getting lost in the glare of the rising Sun. While it's till dark, look for fainter Spica well to Venus' upper right, and for Saturn above Spica. Look off about twice that distance to Venus' upper left for Arcturus. Saturn's rings have widened to 10° from edge-on, and present an interesting sight along with its larger moons in a small telescope.

Of course, Jupiter shines almost as brilliantly as Venus during the evening, high in the south-southwest. The long-absent South Equatorial Belt continues to re-form, as dark markings spread east and west around the planet from a storm that broke out in the SEB's latitude about a month ago.

Uranus is still within 2° to the left of Jupiter, and can be spotted in a small telescope. Have a look at Jupiter first, and then look for an object to the upper left of Jupiter with about the same brightness as Ganymede. Ganymede is about magnitude 5.36 where Uranus is very slightly dimmer at about magnitude 5.45. Don't confuse Uranus with the star 20 Pisces (20 Psc,) which is also the same magnitude, but it is somewhat redder, and about halfway in between Jupiter and Uranus.

Neptune is much dimmer at magnitude 7.9, and is still up in the southwest in Capricornus after dark. Look for 5th-magnuitude Mu Capricorni next to it.
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Astronomy From Your Back Yard - 12/08 to 12/14 2010

By Dave Grosvold

If you can get out and observe in the two hours before the coming of dawn this week, Venus blazes in the southeast, even after sunrise. Venus is still at its highest luminosity, at magnitude Ė4.8 and nearly as high as it gets. Can you watch Venus past sunrise with your naked eye? Look for much fainter Spica to Venus' upper right (about 20°,) and for Saturn about 20° above Spica.

In the evenings this week, Mercury remains in view low about the southwest horizon during twilight. Look about 40 minutes after sunset. Mercury fades from magnitude Ė0.4 to +0.1 this week.

On Wednesday Dec 8th, by 7 or 8 PM CST, bright Capella in Auriga is high in the east-northeast. To its right in the east is the Pleiades (M45), or Seven Sisters, and below it is ruddy Aldebaran in Taurus. Below Capella lie Castor and Pollux, the heads of the twins of Gemini. It will be important to know the location of these twins early next week.

As soon as it gets dark on Thursday evening, look for the waxing crescent Moon in the southwest. To the right of the Moon about 7°, is tiny Alpha Capricorni (α Cap.) If you have sharp vision you can barely see that this is a very close double star. You can resolve it easily in binoculars.

Jupiter still shines brightly this week at magnitude -2.5. Just after dusk on Friday evening look far to the lower right of Jupiter for the waxing crescent Moon. Look below Jupiter to the lower left of the Moon for Fomalhaut (FOAM-a-lout), in Piscis Austrinus, sometimes called “the Autumn Star.”

By Saturday evening, the nearly first-quarter Moon this evening forms a roughly equilateral triangle with bright Jupiter to its upper left and Fomalhaut to its lower left. The Moon reaches First Quarter at 7:59 AM CST, on Monday December 13th.

Monday, December 13th near midnight marks the start of the peak of the Geminid meteor shower for this year, and for most observers, it is the highlight of the week. The peak of the shower continues through the night into the morning hours of Tuesday, December 14th. The name “Geminids” refers to the fact that the radiant for this meteor shower appears to come from the heart of the Twins of Gemini. When meteors are traced back to their apparent origin, the paths they followed all converge at a point on the sky known as the radiant.

From now until December 13th, hourly rates increase until a peak of 50-80 meteors per hour is attained. The rate then tapers off until the last Geminids on December 18th, when the rates fall to one every hour or so. Meteor showers occur all the time, but most are very weak. So there may be stray meteors that are not part of the Geminids during this time as well. When you see a meteor, how do you know if it's a Geminid? Trace the path of the meteor back to its apparent origin. If that origin ends up being in Gemini or close to it, then it's probably a Geminid.

The best way to observe the Geminid Meteor Shower is lie back on a chaise lounge with a clear view of the sky toward Gemini. This time of year, be sure to dress warmly, get a thermos of coffee or hot chocolate, and maybe even throw on a blanket or two. As you lie there, look high up and all around the sky, and don't focus in just one place.

Meteors will appear all over the sky, but the majority will appear to have come from the direction of Gemini, so we face the chaise lounge that way. But we scan from overhead down to about 30° up the sky. We also scan off to the right, and then to the left, looking at the big picture rather than focusing in any one area. Don't discount the sky opposite Gemini, either. Meteors can be seen all over the sky. See if you can count the number of meteors you see in an hour's time, and note the time of night.

On a historical note, the Geminid meteor shower appeared suddenly in the latter part of the 1800's. R. P. Greg of Manchester in the UK first noted several meteors that had a radiant in Gemini in December of 1862. Several other observers independently discovered the same activity the same year from the United States.

Early observations in the late nineteenth century reported the hourly rates at about 14 per hour. As the century waned, the hourly rate seemed to increase to about 23 per hour, with many more bright meteors. These rates have continued to increase throughout the 20th century, averaging about 50 per hour mid-century with the peak rate reaching an average of 80 per hour in the 1980s. The peak hourly rate continues to remain at 80 per hour today. Scientists now think the Geminids are tied to the passage of an asteroid (or minor planet,) 3200 Phaethon, in our solar system across Earth orbit every few years. The Earth passes through the dust and debris left in its wake, creating tiny meteors in our upper atmosphere as we pass.
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Blue Rings around Red Galaxies

NASA Space Placeby Trudy E. Bell and Dr. Tony Phillips

The Galaxy Evolution Explorer UV space telescope helped to identify red elliptical galaxies that also emitted the strongest UV. These are detailed, long-exposure Hubble Space Telescope images of four of these galaxies that capture the UV-emitting rings and arcs indicative of new star formation.
Click image for larger view
Beautiful flat rings around the planet Saturn are one thing — but flat rings around entire galaxies?

That is the astonishing discovery that two astronomers, Samir Salim of Indiana University at Bloomington and R. Michael Rich of UCLA described in the May 10, 2010, issue of The Astrophysical Journal Letters.

“For most of the twentieth century, astronomers observing at visible wavelengths saw that galaxies looked either ‘red and dead’ or ‘blue and new,’” explained Salim. Reddish galaxies were featureless, shaped mostly like balls or lentils; bluish ones were magnificent spirals or irregular galaxies.

Elliptical galaxies looked red, astronomers reasoned, because they had mostly old red giant stars near the end of their life cycles, and little gas from which new stars could form. Spiral and irregular galaxies looked blue, however, because they were rich in gas and dust that were active nurseries birthing hot, massive, bluish stars.

At least, that's how galaxies appear in visible light.

As early as the 1970s, though, the first space-borne telescopes sensitive to ultraviolet radiation (UV) revealed something mysterious: a few red elliptical galaxies emitted “a surprising ultraviolet excess,” said Rich. The observations suggested that some old red galaxies might not be as “dead” as previously supposed.

To investigate, Salim and Rich used NASAís Galaxy Evolution Explorer satellite to identify 30 red elliptical galaxies that also emitted the strongest UV. Then they captured a long, detailed picture of each galaxy using the Hubble Space Telescope.

“Hubble revealed the answer,” says Salim. The UV radiation was emitted by enormous, flat bluish rings that completely surrounded each reddish galaxy, reminiscent of the rings of Saturn. In some cases, the bluish rings even showed a faint spiral structure!

Because the bluish UV rings looked like star-forming spiral arms and lay mostly beyond the red stars at the centers of the elliptical galaxies “we concluded that the bluish rings must be made of hot young stars,” Salim continued. “But if new stars are still being formed, that means the red-and-dead galaxies must have acquired some new gas to make them.”

How does a galaxy “acquire some gas?” Salim speculates that it was an act of theft. Sometimes galaxies have close encounters. If a gas-rich irregular galaxy passed close to a gas-poor elliptical galaxy, the gravity of the elliptical galaxy could steal some gas.

Further studies by Galaxy Evolution Explorer, Hubble and other telescopes are expected to reveal more about the process. One thing is certain, says Rich: “The evolution of galaxies is even more surprising and beautiful than we imagined.”

The press release is available at http://www.galex.caltech.edu/newsroom/glx2010-03f.html. The full published article is “Star Formation Signatures in Optically Quiescent Early-Type Galaxies” by Samir Salim and R. Michael Rich, The Astrophysical Journal Letters 714: L290ĖL294, 2010 May 10.

Point the kids to the Photon Pile-up Game at http://spaceplace.nasa.gov/en/kids/galex/photon, where they can have fun learning about the particle nature of light.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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Help Juno cut through Jupiterís veil

NASA Space Place
Hey kids! The roman god Jupiter (for whom the planet is named) drew a veil of clouds around himself to hide his mischief. Jupiter's wife, the goddess Juno, had the power to peer through the clouds and see Jupiter’s true nature. NASA’s Juno spacecraft, to be launched next summer, will also look beneath the clouds to reveal Jupiter’s mysteries. Get a Juno-view of Jupiter by playing the exciting new JunoQuest game at The Space Place, http://spaceplace.jpl.nasa.gov/en/kids/juno.
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Astronomy From Your Back Yard - 12/01 to 12/07 2010

By Dave Grosvold

On Friday morning, about 1/2 hour before dawn, look for a razor-thin crescent Moon far below Venus in the southeastern sky. Venus is at its maximum brightness magnitude Ė4.9, and as is commonly known as the “Morning Star”. Far above Venus is Spica in Virgo, and above that, Saturn at magnitude +0.9. Saturn's rings are 9° or 10° from edge-on now, and early dawn is the best time to observe the ringed planet all this week.

Early in the evening all week, the constellation Cassiopeia floats very nearly directly overhead when you face north. Look for an M-shaped grouping of stars high above you for Cassiopeia. About halfway from Cassiopeia to the horizon lies Polaris, the North Star. Polaris is the brightest star in the otherwise dim constellation of Ursa Minor, commonly known as the Little Dipper.

Far below Polaris, and very nearly below the horizon, lie the upper-most stars of the Big Dipper asterism, part of the constellation of Ursa Major. The tail of Draco wends its way between Polaris and the stars of Ursa Major. This far south, you may not even be able to spot the stars of Ursa Major without finding a nearly flat horizon clear of obstructions.

Jupiter shines high in the south to southwest during evening, the brightest star-like point in the evening sky. Jupiter's missing South Equatorial Belt is finally starting to re-group, becoming barely visible as dark material spreads from a series of telltale bright storm spots that appeared three weeks ago.

On Friday evening, Jupiter's moon Europa reappears from eclipse out of Jupiter's shadow around 7:30 PM CST. Watch and wait for a few minutes, and a small telescope will show it gradually become visible just east of the planet.

Later in the evening, look to the east to see the starry harbingers of Winter, orange Aldebaran in Taurus, fiery red Betelgeuse and blue-white Rigel in Orion, bright yellow Capella in Auriga, the TwinsCastor and Pollux in Gemini, brilliant blue-white Sirius, the brightest star in the sky — and the brightest in Canis Major. Don't forget the white binary star system Procyon in Canis Minor, considered the seventh brightest in the sky. Betelgeuse, Sirius, and Procyon make the three vertices of the Winter Triangle asterism.

Mercury, at magnitude Ė0.4 is now at the best time for observing its current evening apparition. Still, it's quite low on the horizon, and a challenge. Look for it in mid-twilight just above the southwest horizon.

New Moon occurs on Sunday, December 5th at 11:36 AM CST, so both Saturday evening and Sunday evening will be good times to observe deep-sky objects (those outside our Solar System.)

This week is a great time to see Iridium Flares, both in the morning and evening. At 6:02 PM CST on Sunday, December 5th, Iridium 63 flares to magnitude -0 low in the western sky at an altitude of 11°. Just a few minutes later at 6:37 PM CST, Iridium 49 flares to magnitude -2 at an altitude of 30° in the south. Early Monday morning, at 7:01 AM CST, Iridium 46 flares to an absolutely brilliant -8 magnitude high up in the sky at 71° altitude. Look for it at azimuth 339° (in the NNW.) This is the brightest flare that will occur over the coming week.

Monday evening, Iridium 65 and 66 put on a show at 5:47 PM and 5:56 PM CST, respectively. Iridium 65 will flare to magnitude -1 and Iridium 66 will reach magnitude -2. Both satellites will be low (at altitudes of 13° and 10°) in the Western sky. On Tuesday morning at 6:55 AM CST, we see Iridium 46 reach a fairly bright magnitude -5, pretty high up at an altitude of 69° in the NNW, and then Tuesday evening at 5:41 PM CST, Iridium 68 also flares to magnitude -5 low at an altitude of 14° in the Western sky. You can find out more about these at the Heavens Above web site.
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Astronomy From Your Back Yard - 11/17 to 11/23 2010

By Dave Grosvold

Unfortunately, business travel demands have kept me away from this column for a couple of weeks. It's good to be back! Well, it looks like there will be some clear skies and great opportunities for night-time sky watching Thursday through Sunday this week. To get a better idea how the night sky viewing will be for the next two evenings, check out the Fort Smith Clear Sky Chart. This chart will tell you how dark the sky will be, when you can expect cloud cover during the night, and what transparency and seeing conditions are expected.

On Wednesday evening, Jupiter will be slightly higher and about 20° to the right of the waxing gibbous Moon. The Moon reaches the Full phase on Sunday, November 21 at 11:28 AM CST. As a result, it will be a bright beacon in the night sky all week, washing out all but the brightest stars and planets. There will be early-morning dark skies late this week (Thursday & Friday,) as the Moon sets at about 3:00 AM CST on Thursday morning, setting about an hour later each morning until later in the week when it remains visible the entire night.

The bright star Vega in the constellation Lyra remains the brightest star in the west-northwest these evenings. The brightest star higher above it is Deneb in the constellation Cygnus. To the left of Vega lies the third member of the Summer Triangle, Altair, in the constellation Aquila. Both the cool crisp air and the Summer Triangle low in the western sky are sure signs of approaching winter.

For a challenge this week, use binoculars to scan for Mercury very low in the southwest less than a half hour after sunset. Mars is less than 2° to Mercury's upper right. If you place Mercury in the lower left of the field of view, you should be able to detect fainter Mars above and to the right.

By 9:00 PM CST Saturday, November 20th, the constellation Orion has risen in the east-southeast. Look for it far below this evening's high, bright Moon. The three unmistakable belt stars in Orion will be lined up vertically, with the bright blue-white star Rigel on the right, and fiery-red Betelgeuse on the left.

Halfway between Betelgeuse and the Moon is another bright red star, Aldebaran, in Taurus. Draw an imaginary line from the Moon down through Aldebaran to Betelgeuse, and then imagine a line perpendicular to the first one, to the left of Adebaran you should see the bright yellow star Capella, in the constellation Auriga.

On Sunday evening, the Full Moon passes just below the Pleiades (M-45,) an open cluster in the constellation Taurus. At closest approach the Moon is just slightly more than 4° from the center of the Pleiades, or just over the width of two fingers held at arm's length.

This week, Venus is rising ever higher at dawn in the east-southeast. Look a little above it or to its upper right for much-fainter Spica in Virgo. Look higher (about 16°) above it for Saturn. Saturn's rings have widened to a tilt of about 9° from edge-on. The best time for observing Saturn with a telescope is about an hour before sunrise, or about 6:00 AM local time, when the planet will be above the “muck” -- the haze and turbulence found close to the horizon.

You may also be able to catch a couple of bright Iridium Flares this week. Iridium 41 flares to -6 magnitude at 4:51 AM CST on Thursday morning. Look for it in the south at an altitude of 21°. Then on Sunday evening at 5:58 PM CST, you can catch Iridium 66 flare to magnitude -7 in the south at an altitude of 33°. Early on Monday morning, Iridium 62 flares to magnitude -4 nearly overhead at an altitude of 59° in the north-northwest. There are a several other chances to catch Iridium Flares, this week albeit at dimmer magnitudes. Be sure to check the web site at Heavens Above for times and positions.
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Astronomy From Your Back Yard - 10/27 to 11/2 2010

By Dave Grosvold

This week the Moon is well on its way toward Last Quarter, which occurs at 7:47 AM Saturday, Oct 30th. Forecasts call for several clear evenings into the weekend, an excellent opportunity for a little night sky observing -- especially since the Moon won't rise until after 11:00 PM CDT.

NASA, ESA, AURA/Caltech, Palomar Observatory
During the latter part of the week, yellow-bright Capella is shining in Auriga, well up in the northeast by mid-evening. Look off to its right in the east for the Pleiades, or Seven Sisters.

The beautiful Pleiades (PLEE-ah-deez,) star cluster is also known as Messier 45 (M45), one of the original 103 objects Charles Messier catalogued in 1771 as objects to avoid while comet hunting, which was his main passion. Messier's list became better known to history as the first list of interesting non-stellar objects in the night sky.

The Pleiades are probably the most well-known star cluster visible to the naked eye. A group of young, blue-hot stars surrounded by nebulosity, the cluster is thought to be less than 100 million years old. By contrast, the Sun is thought to be more than 4.6 billion years old. In Japan, the Pleiades cluster is known as Subaru, and is graphically depicted as the corporate logo for the automaker of the same name.

Below the Pleiades, spaced by about a fist-width at arm's length, is the orange giant Aldebaran, the brightest star in the constellation Taurus. A close neighbor, Aldebaran lies only about 65 light years distant from our Solar System. Aldebaran (Al-DEB-a-ran) means “the follower”, presumably because it appears to follow the Pleiades. For the Seris of northwestern Mexico, Aldebaran is there to provide light for the seven women giving birth (the Pleiades.)

Every year for several days around October 29th, the bright star Arcturus, in BoŲtes, takes a special position sparkling in the fading twilight low on the west-northwestern horizon. This position marks the spot where, months earlier in June and July, the Sun stood at the exact same time of the evening. Then, the summer daylight was still strong in the evenings, now the autumn light is fading and this much smaller, scintillating gem is all that remains in the west, the Ghost of the Summer Sun, marking the mid-point of autumn.

Mars is still hanging around very low in the southwest after sunset as well. Use binoculars to scan for it early in twilight. Don't confuse Mars with Antares, which is off to Mars' left and just a tiny bit brighter. The name Antares comes from Ancient Greece, so named because the star can easily be mistaken for Mars. Antares literally means "holds against Ares" (Ares is also known as Mars in Roman mythology.)

Jupiter still shines high in the southeast between Pisces and Aquarius rising high into the south-southeast as the evening wears on. Right now, it is by far the brightest star-like point in the sky. Jupiter continues to appear a big 47 or 48 arc-seconds wide in a telescope or binoculars.

Once again, the tiny black shadows of two of the Galilean Moons, Europa and Ganymede, fall on Jupiter's face from 11:16 PM CDT Saturday evening to 1:59 AM CDT Sunday morning. These can only be caught with the aid of a small telescope -- binoculars won't do.

Saturn is visible in Virgo, low in the east in early dawn. The best time to try observing it with a telescope is in moderately bright morning twilight, perhaps an hour before sunrise, when it will be less blurred by the low-altitude atmospheric mess. Saturn's rings have opened to 7į or 8į from edge-on, and so are more prominent than they were just a few months ago.

Uranus is still within 3į east of Jupiter. Neptune, in Capricornus, is high and almost due south at about 9:00 PM CDT.
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Power Without Pollution

NASA Space PlaceHey kids! Harness the wind and the sun! Power up a whole town without creating any pollution or greenhouse gases. “Power Up!” is the new game on NASA’s Climate Kids web site. In this game, your progressive town gets all its energy from wind turbines and solar panels. You have just two minutes to capture enough wind and solar energy to light up all the windows in all the houses of the town. If you succeed, you win the Platinum Award for clean energy. If just a few windows are still dark, you win the Gold. Silver and Bronze Awards are good, but you’ll learn to do even better. Try this fun new game at http://climate.nasa.gov/kids/powerupcleanly.
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Close Encounters with Jupiter

NASA Space Placeby Dr. Tony Phillips

The Juno mission, arriving at Jupiter in July 2016, will help to solve the mystery of whatís inside the giant planetís core.
Click image for larger view
Jupiter and Earth just had a close encounter — and it was a good one. In late September 2010, the two worlds were 31 million km (about 19 million miles) closer than at any time in the past 11 years. Soaring high in the midnight sky, Jupiter shone six times brighter than Sirius and looked absolutely dynamite through a backyard telescope. Planetary scientist Scott Bolton of the Southwest Research Institute isnít satisfied. “Iíd like to get even closer,” he says.

Bolton will get his wish in July 2016. Thatís when a NASA spacecraft named “Juno” arrives at Jupiter for a truly close-up look at the giant planet. Swooping as low as 5,000 km (about 3,000 miles) above the cloud tops, Juno will spend a full year orbiting nearer to Jupiter than any previous spacecraft.

The goal of the mission is to learn what lies inside the planet.

Astronomers have been studying Jupiter since the invention of the telescope 400 years ago, but in all that time the planetís vast interior has remained hidden from view. Even the Galileo probe, which dived into the clouds in 1995, penetrated no more than about 0.1% of Jupiterís radius.

“Our knowledge of Jupiter is truly skin deep,” says Bolton, Junoís principal investigator. “There are many basic things we just donít know — like how far down does the Great Red Spot go? And does Jupiter have a heavy core?”

Juno will improve the situation without actually diving into the clouds. Bolton explains how. “Juno will spend a full year in close polar orbit around Jupiter, flying over all latitudes and longitudes. We will thus be able to fully map Jupiterís gravitational field and figure out how the interior is structured.”

But thatís not all. Researchers have good reason to believe that much of Jupiterís interior is filled with liquid metallic hydrogen, an exotic metal that could form only in the high-pressure, hydrogen-rich core of a giant planet. Jupiterís powerful magnetic field almost certainly springs from dynamo action inside this vast realm of electrically conducting metal.

“Junoís magnetometers will precisely map Jupiterís magnetic field,” says Bolton. “This map will tell us a great deal about planetís inner magnetic dynamoówhat itís made of and how it works.”

Finally, Juno will probe Jupiterís atmosphere using a set of microwave radiometers. “Our sensors can measure the temperature 50 times deeper than ever before,” says Bolton. Researchers will use that information to figure out how much water is underneath Jupiterís clouds. “Microwave measurements of Jupiterís water content are particularly exciting because they will help discriminate among competing theories of the planetís origin.”

Now thatís a close encounter. Stay tuned for Juno.

Find out more about the Juno mission at http://www.nasa.gov/mission_pages/juno. Play the new Solar System Explorer super game, which includes the Juno Recall mini-game at http://spaceplace.nasa.gov/en/kids/solar-system. Itís not just for kids!

This article was provided courtesy of the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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Astronomy From Your Back Yard - 10/20 to 10/26 2010

By Dave Grosvold

The Full Moon occurs this week at 8:37 PM, CDT on Friday, October 22nd. The nearly full Moon washes out the sky for the entire night on Wednesday and Thursday evenings, since it will rise before sunset and will not set again until nearly dawn. However, the Moon rises about 30 minutes later each evening, so by Tuesday, October 26th, the waning gibbous Moon will not be in the sky until after 9:00 PM CDT.

Although both the bright glow of the Moon and the weather forecast don't look favorable for astronomical observing this week, you may still be able to catch a glimpse of Comet 103P/Hartley in binoculars or a small telescope. Look for it in the constellations Auriga and Gemini in the eastern sky at about 12:30 AM CDT. Whether you'll see the comet or not depends to a great degree on the quality of the sky when you make the observation.

This week, the Big Dipper asterism in Ursa Major lies level in the north-northwest after dusk, quite low, far below the bowl of the much dimmer Little Dipper (Ursa Minor).

On Thursday evening, the Great Square of Pegasus asterism is straight above the waxing gibbous Moon after dark. The Great Square is tipped on one corner and somewhat larger than your fist held at arm's length. The Great Square is actually part of two constellations - its namesake Pegasus, and Andromeda.

Mars is getting dimmer at magnitude 1.5, which is still fairly bright as astronomical objects go. Mars continues to linger very low in the southwest right after sunset.

Even with the moon glow, bright Jupiter is an easy target in the constellation Picses. Jupiter is still within its first month past opposition, and has just passed a very close approach to Earth, — perfectly positioned for viewing mid-way up the east-southeastern sky, reaching its highest point at about 11:00 PM.

On Saturday, October 23rd, see if you can catch the tiny black shadows of both Ganymede and Europa as they pass across Jupiter, from 8:40 to 10:04 PM CDT.

Saturn is back as a morning planet, just emerging from the sunrise glow. Look for it in the constellation Virgo, very low in the east about an hour before sunrise. It's within 1į of fainter Gamma Virginis.

Neptune, at magnitude 7.8 in Capricornus, is still highest in the south about an hour after sunset. With the expected sky conditions this week, Neptune will be a difficult target. You will need a small telescope to catch it.

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