Monthly Archives: September 2011

WISE asteroid survey gives Earth a moment of relaxation

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NEOWISE observations indicate that there are at least 40% fewer near-Earth asteroid that are larger than 330 feet. Our solar system's four inner planets are shown in green, and the sun is at center. Each red dot represents one asteroid. Object sizes are not to scale. Image credit: NASA/JPL-Caltech

Good news on potential asteroid troubles for tender-hearted Earth. NASA announced yesterday that a recent study of the sky by the Wide-field Infrared Survey Explorer (WISE) determined that there are significantly fewer mid-sized asteroids in Earth’s neighborhood by a factor of almost a half. Previously, scientists had estimated the number of space rocks with sizes ranging from 330 to 3,330 feet within 120 million miles of our planet at 35,000. That’s now been revised downward to about 19,500. Fewer near-Earth asteroids means fewer potentially hazardous bodies causing trouble for our planet in the future.

WISE scanned the entire sky twice during the asteroid-hunting portion of its program called NEOWISE (Near Earth Objects) between January 2010 and February 2011 taking pictures of everything from galaxies to comets to asteroids in the light of infrared. Infrared light, which lies just beyond the red end of the rainbow spectrum, is sensed by us as heat. When you boil a pot of water for tea, your teaport becomes a powerful emitter of infrared light. Telescopes can be designed to gather infrared light just like ordinary visible light, but their detectors must be chilled to near absolute zero, so the images aren’t overwhelmed by the heat of the instrument. The WISE detector was surrounded by frozen hydrogen in an “ice chest” at -430 F !

This chart shows how data from NASA's Wide-field Infrared Survey Explorer, or WISE, has led to revisions in the estimated population of near-Earth asteroids. Image credit: NASA/JPL-Caltech

NEOWISE observed more than 100,000 asteroids in the main belt between Mars and Jupiter in addition to 585 near Earth. Observing in infrared light allowed WISE to make the most accurate asteroid population census ever. In visible light, darker-colored asteroids  are hard to detect because they reflect so little light and therefore are exceedingly faint. Asteroids covered in lighter materials are much easier. With an ordinary telescope, these small, chalky-bright asteroids appear similar in brightness to much larger, charcoal-toned ones. Telling size becomes a tricky business. Infrared light has no bias. If an asteroid’s small, it radiates less heat than a bigger one, making it easier to determine accurate sizes and potential threats.

Not only did WISE update the mid-size asteroid count, but its findings indicate that NASA, through a variety of asteroid detection programs both satellite and ground-based, has detected more than 93% of the largest near-Earth asteroids, defined as those 1 kilometer (0.62 mile) and larger. These mountain-sized rocks would cause significant destruction and climate change if one were to collide with our planet.

This chart illustrates why infrared-sensing telescopes are more suited to finding small, dark asteroids than telescopes that detect visible light. Albedo is the amount of light an asteroid reflects. Light-colored ones reflect more brightly (high albedo) than dark ones (low albedo). In infrared light, there is no bias - large asteroids are brighter and small ones fainter. Image credit: NASA/JPL-Caltech

“The new data revise their total numbers from about 1,000 down to 981, of which 911 already have been found. None of them represents a threat to Earth in the next few centuries. It is believed that all near-Earth asteroids approximately 6 miles  across, as big as the one thought to have wiped out the dinosaurs, have been found,” according to the agency.

Don’t get too comfortable just yet. NASA’s Spaceguard NEO Survey currently tracks 5,200 mid-sized and larger asteroids with an estimated 15,000 left to discover. A mid-sized asteroid would destroy a city in a direct hit. As for near-Earth bodies under 330 feet, scientists believe more than a million are buzzing around within 120 million miles of the planet. Some are potentially capable of damage.

What I find most interesting about the survey results is the picture they paint of what seems to be a very busy neighborhood. However the fact that asteroid impacts are extremely rare tells us that there’s still a lot more empty space out there than rocks.

Mars takes up beekeeping

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Clouds and local light pollution compete with the green of northern lights in this photo taken last night. Auroras have colored the sky three nights in a row in northern Minnesota, and there'a s a good chance for more tonight. Photo: Bob King

One way or another, I’m going to coax you out under the dawn sky. If the sight of Orion, the zodiacal light and Comet Honda aren’t enough, Mars is headed straight for the center of the Beehive Star Cluster over the next few mornings. The Beehive is located in Cancer the Crab, one of the fainter constellations of the zodiac found below Gemini the Twins. This bright stellar bunch is 577 light years from Earth and one of the Milky Way galaxy’s many open star clusters. Its nickname derives from the resemblance to a swarm of buzzing bees, albeit one frozen in a moment in time.

Mars is easy to find with a little help from its friends. The planet is still relatively far from Earth and only moderately bright. Face east-southeast before dawn and use the Belt of Orion and brilliant star Sirius to help point you to the planet. The Beehive is the fuzzy spot right next door. Maps created with Stellarium

If your skies are free of light pollution, the cluster is easy to see with the naked eye as a misty patch of light. The ancient Greek astronomer Hipparchus included it in his star catalog in 130 B.C. calling it the “Little Cloud.”Tomorrow morning you’ll see Mars encroaching along the cluster right or western border. Any pair of binoculars will transform the fuzzy spot into a patch of many stars. Galileo was the first to observe it and counted some 40 stars. You’ll see even more with today’s much better optics. Since the Beehive is about a degree across (two full moons side by side), binoculars are the perfect tool for the best view. Most telescopes magnify too much, spreading out and diluting the pretty “cluster” effect.

This view is similar to what you'll see through binoculars as Mars marches across the cluster over the next three mornings.

On Saturday morning, Mars will be squarely in the center of the Beehive surrounded by all those bright little bees. If you have a digital camera that can do a time exposure, this would make a great photo opportunity.  By Sunday morning, the Red Planet will have departed the cluster. While you’re looking at the two, try to picture Mars much closer to us in the foreground with the star cluster far, far away in the background. Anytime between 3 and 5:30 a.m. is good for viewing, though the later you’re out, the higher and easier the two will be.

Still not enough reason to set the alarm and get up before the sun? The International Space Station continues to make lots of fine passes across the morning sky. The times shows below are for the Duluth, Minn. region. For times for your town, just click HERE and enter your zip code.

* Friday Sept. 30 starting at 5:19 a.m. across the northern sky.
* Saturday Oct. 1 at 5:54 a.m. on a similar path
* Sunday Oct. 2 at 4:57 a.m. starting in the north-northeastern sky

A 2-day old moon hangs low in the sky during twilight this evening.

And if you still don’t feel like a dawn pilgrimage, then consider the return of the moon this evening. Starting tonight you’ll see a thin lunar crescent shortly after sunset very low in the southwestern sky.  Catch it early, as it sets within an hour of the sun. In the coming nights, the moon’s orbital motion about the Earth will cause it to rise higher and stick around longer before setting.

Comet Honda visits the ghost of comets past

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The figure of Orion with his "three in a row" belt stars stood high above the trees this morning around 5 a.m. Details: 35mm lens at f/2.8, ISO 1600 and 25 second exposure. Photo: Bob King

I really should do my winter sky observing in September. The only obstacle is having to get up before dawn. During the evening hours, we see the stars of late summer and early fall – Cassiopeia, the Summer Triangle, the Great Square of Pegasus. But as we sleep, the Earth turns and by 4 o’clock in the morning, Orion the Hunter and Gemini the Twins are high in the east and ripe for plucking with binoculars and telescope.

This stunning color photo of Comet Honda was made with a wide-field 8-inch telescope on Sept. 26 and shows the bright coma and long ion tail. Comets often have two tails: one of dust that reflects sunlight and another of gas set aglow by ultraviolet light from the sun. Click image to see a Quicktime movie of the comet showing changes in the tail. Credit: Michael Jaeger

What a sight to see Orion beneath trees still green and in temperatures well above freezing. That was the view this morning when I stumbled out to see Comet Honda-Mrkos-Pajdusakova low in the eastern sky near the start of twilight. After a peek at the Orion Nebula, I aimed the 15-inch telescope to a spot just below the bright star Regulus and bingo! Using my lowest magnification of 64x the comet was a tight, bright ball of light with the most delicate, lovely ion tail streaming away to the west. Shining at magnitude 6.5 (just below naked eye limit), Comet Honda looked like a faint star wrapped in a bit of fuzz through 8×40 binoculars. Even a 25-second exposure picked up the telltale green color of cyanogen, a glowing gas found in the comas or atmospheres of many comets.

Even this 25-second long exposure at ISO 1600 captures the green glow and short trail of Comet Honda this morning. The comet is located smack in the middle of the zodiacal light. Photo: Bob King

The comet will slowly fade over the next few weeks as it moves eastward in Leo. It passed closest to Earth back in August and is now pulling away with a current distance of about 75 million miles. For a map to help you find it, click over to this earlier blog.

The only snag to seeing the comet is its low altitude — only about 10 degrees or “one fist” high at the start of dawn 1 1/2 hours before sunrise. If you can find a place with a wide open view toward the east, you’re in business. While we may never get to see Comet Elenin post-breakup, Comet Honda makes for a solid stand-in.

In the same direction there’s a much larger phenomenon visible with the naked eye to those with dark, light-pollution free skies. Every fall when the moon has departed the morning sky, the “thumbprint” of the zodiacal (Zoh-DYE-uh-cull) light makes its appearance in the east just before the start of morning twilight for observers at mid-northern latitudes.

The weakly glowing zodiacal light reaches up from the eastern horizon along the zodical constellations this morning. Details: 18mm lens at f/2.8, ISO 1600 and 30-second exposure. Photo: Bob King

This large, oval or cone-shaped glow, which is composed of minute dust particles shed by passing comets,  spreads through plane of the solar system called the ecliptic. In fall, the ecliptic is steeply tilted upwards in the east in the wee hours of morning, “lifting” the dim, diffuse zodiacal light high enough to clear the lower, hazy air and improve its visibility.

If you’d like to see it, anytime in the next week and a half is ideal, since the moon won’t disturb the darkness required to see this curious cometary remnant. If you miss it this month, you’ll have another chance in late October. The cone is widest near the eastern horizon in Leo and narrows as you direct your gaze upward and to the right. The best way I’ve found to spot it is to turn your head left and right while facing east and look for a large, soft haze similar to but a bit fainter than the Milky Way.

It’s a fun coincidence that Comet Honda, which is shedding dust as it departs the Earth’s vicinity, is making its own contribution to the zodiacal light, ensuring that future generations of sky watchers will always have this otherworldly sight to look forward to. To learn more about it, click HERE.

The red circle shows UARS final resting place. Credit: NASA

One final news note. NASA announced yesterday that the Upper Atmosphere Research Satellite (UARS) everyone including myself was so excited about last weekend fell back to Earth at 11 p.m. Central time Sept. 23 over the South Pacific Ocean not far from American Samoa. Any debris remaining from the burn-up is probably sitting at the bottom of miles of water. No sightings of the re-entry have been reported.

Aurora pix! Take a seat in Andromeda’s time machine

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Great aurora scene taken from Rimsfora, Sweden last night. Details: Nikon D5000 camera, f/3.5 18mm lens at ISO 3200. Credit: Krzysztof Polakowski

It was painful to look at the auroral plots and satellite images last night and know the northern lights were happening only 4 miles away … through an impenetrable layer of clouds. Walking the dog around 9 p.m., I could see a pale glow through broken clouds in the northern sky. Five minutes later even that filled in.

Reed Ingram Weir of Northumberland, UK captured this colorful rayed arc last night. The clouds add a special touch.

Thanks to clear skies and alert eyes elsewhere, we can still enjoy the nice show. Northern lights were reported across northern Europe and the northern U.S. last night. Tonight there’s still a good chance for auroras due to high speed material arriving from earlier eruptions in sunspot group 1302. Let’s hope the weather forecast is equally optimistic.

The moon is new today leaving us dark evening skies now through the weekend. Why not go out and try to see the farthest thing you can see without a telescope? That would be the Andromeda Galaxy in the constellation of Andromeda the Princess. You might be surprised at how easy it is to find. And you won’t need a cabin in the country to do this. The galaxy, the closest large galaxy to our Milky Way galaxy, is visible from moderately dark skies such as those you’d find on the outskirts or suburban areas of smaller cities.

This map shows the sky facing northeast around 8:30 p.m. local time. The Andromeda Galaxy is one "Cassiopeia width" to the lower right of that constellation. If you have difficulty seeing it, play your eye around the spot rather than stare directly at it. This technique, called averted vision, exposes the low-light-sensitive part of the eye to the galaxy. Created with Stellarium

The key is allowing your eyes about 10-15 minutes to adapt to the darkness. Once you can see your way around, look about halfway up in the northeastern sky around 8:30-9 p.m. and find the zigzag or W-shaped constellation Cassiopeia. It spans an amount of sky equal to about one fist held at arm’s length. Now pretend that the top half of Cassiopeia is really the tip of an arrow. If you follow where it points, it will take your gaze directly to a small, fuzzy patch of light – the Andromeda Galaxy.

The Andromeda Galaxy is the closest bright galaxy beyond the Milky Way system. The hazy disk and bright nuclear region are actually billions of stars that blend into an unresolved glow. The dark stripes are lanes of interstellar dust within the galaxy's spiral arms, while the smaller galaxy below is a satellite galaxy revolving around larger Andromeda. Photo: Bob King

It looks like a bit of fluff or haze to most of us. Those with darker skies and keener vision can detect the galaxy’s brighter, more concentrated core set in a faint oval disk. Binoculars will show the shape, large size and bright nucleus very clearly. No matter how you see it, your vision will reach across a distance of 2.5 million light years and into the depths of time.

Time? Yes, the light from everything we see in the celestial vault takes time to get here even though it’s traveling at 186,000 miles per second. Sunlight requires nearly 8 minutes to reach Earth 93 million miles away. The light from Jupiter, which is currently 381 million miles from Earth, takes 34 minutes to get here; Pluto’s requires 4 1/2 hours! Once we get to the stars, we’re dealing with years and years. Whatever that star’s distance in light years, that’s how old the light reaching our eyes will be tonight. Vega is 25 light years from us, so we see the star as it was 25 years ago.

As for the Andromeda Galaxy, the light you see tonight left it at the beginning of the Stone Age, when our human-like ancestors first starting making stone tools. It’s quite a time shock when it hits you.

This image from the Hubble Space Telescope shows individual stars in a small part of the disc of the Andromeda Galaxy, the closest spiral galaxy to the Milky Way. Credit: NASA/ESA

Andromeda is a spiral galaxy similar to our Milky Way. If we could orbit on a planet about a star in the galaxy we’d see all stars around us just as we do on Earth. There would even be an “Andromeda Way” similar to the hazy band of distant starlight light we call the Milky Way (which is also the name of our galaxy). Andromeda has its own star clusters, gas clouds called nebulas, sun-like stars and undoubtedly planets set in a flattened, self-contained disk at least 220,000 light years across.

We look to Andromeda as September becomes October and recognize a familiar face across the vastness of space.

 

Sun grows a monster spot

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Sunspot region 1302 is bursting with activity including two large X-class flares late last week. Its busy magnetic configuration makes more large flares likely this week. The group is larger than the planet Jupiter. Credit: NASA/SDO

I just got in from observing the sun with my little refracting telescope. My attention was riveted by a huge sunspot group on the eastern half of the sun’s disk that’s been growing larger and feistier by the day. I even saw it without any telescope at all through a pair of safe filtered glasses. Naked-eye sunspots you can see from your own front yard are uncommon and quicken the pulse of any solar observer.

I use a basic 80mm (3-inch) refracting telescope equipped with a safe reflective glass solar filter to quick and easy views of the sun. Photo: Bob King

Solar weather forecasters with NOAA’s Space Weather Prediction Center are calling for minor to major magnetic storms from a coronal mass ejection (CME) associated with a hefty flare from the group that popped off on the 24th. In basic English, that means there’s a possibility for auroras tonight across the northern U.S. and southern Canada. Because the spot group has a jumbled mix of north and south magnetic poles all within close proximity, chances are excellent that opposite poles will encounter one another and release powerful energy in the form of solar flares, increasing the chances for more northern lights in the coming week. And since the group is rotating closer to the center of the sun, any CMEs that occur are more likely to be directed toward Earth. ** UPDATE 9/26 at 11:30 p.m. — aurora is out over northern U.S.  Seen briefly in Duluth, Minn. before clouds moved in.

Sunspot region 1302 was an obvious dark dot this morning when viewed through solar filter glasses.

Timing couldn’t be better. The last modest auroral display was mostly washed out by  September’s full moon. This week the moon is now around new phase and won’t cause any problems. If you’re interested in observing the sun through your telescope, it’s essential to use a safe glass or optical mylar solar filter. These are available from a variety of vendors including Orion Telescopes. Wherever you purchase yours, make sure it’s the kind that fits over the front end of the telescope to ensure the safest filtration.

Inexpensive sun-viewing glasses use a safe black optical mylar for lenses. Photo: Bob King

If you don’t own a telescope but would like to follow the progress of naked eye sunspots like group 1302, check out the “eclipse shades” from Rainbow Symphony. The glasses are made of cardboard with a safe, quality optical filter that gives a crisp image of the sun.

Sun watching is fun, easy and very rewarding as you follow the day-by-day march of spot groups across the disk. Old ones fade and new spots can pop up overnight.

A starry night with friends, “E” Day for Comet Elenin looms

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The "Jellyfish" created with red flashlight and green lasers on an old grain silo. Photo: Bob King

I truly need to catch up on sleep. I’ve been up until 2 or later the past couple nights. For good reason. Last night I attended the Furtman Farm Star Party in northern Wisconsin, an annual gathering of starry-eyed men and women who will stop at nothing – neither frost, nor dew nor the sweet whispers of sleep – to track down comets, star clusters and the finest details of Jupiter’s cloud belts at all hours of night. We were fortunate to have clear skies and steady seeing as well one fellow who could bark like a coyote. Between hunting carbon stars and globular star clusters, he barked a lone coyote almost to within petting distance. OK, I exaggerate, but just a little.

After we’d had our fill of the celestial vault, we took a break to “laser paint” a big, old grain silo on the property in what’s becoming an annual tradition. After a half dozen free-form portraits based loosely on Christmas trees, fires, stars and joists of light, we were suddenly hungry. Under the dim red light our happy host Greg Furtman installed in his kitchen, our group enjoyed all kinds of snack food including so-called “Five Alarm” hot peanuts. After much sampling and debate we agreed they were closer to 2.5 alarms.

Our group returned to the dewy cold and peered at the fantastic spots and belts of Jupiter until 1:30 a.m. I drove home fortified by the pleasures of laughter, conversation and friendship shared with one of the finest groups of people on the planet … on any planet.

Comet Elenin is still not visible in images taken today through Sept. 30 (updated) by SOHO. The stars are Eta and Beta in the constellation Virgo. Credit: NASA/ESA

Tomorrow Comet Elenin will pass closest to the sun in the sky as seen from Earth. Don’t get too excited, because there will be nothing to see. First, let’s dispel the baloney about the comet blocking the sun. It’s not only much, much too small to accomplish this, but we’re not even sure there’s a comet there anymore. Elenin started falling to pieces in late August and by the time of last telescopic observation some 11 days ago, it had faded to below 10th magnitude – dim! More importantly, Comet Elenin will NOT pass in front of the sun, because its orbit takes it some 2.2 degrees or four full moon diameters above the sun. That’s a complete miss!

This is how the sky will look around 11 p.m. Monday night the 26th when Comet Elenin is in conjunction with the sun. At the time, the sun will be up in Asia. Please note I've "removed" the atmosphere, so you can see where the moon, planets and comet are in relation to the sun. None of these are otherwise visible because of daylight glare. Mercury appears close to the comet, but it's far in the background on the opposite side of the sun. See diagram below for a side view of Earth and Elenin. Maps created with Stellarium

When a planet or comet or other celestial object lines up closest to the sun on a north-south line, we say the two bodies are in conjunction. Conjunctions are very common, happening all the time during every year. Saturn was in conjunction with the sun this summer and Mercury will be on September 28. Not a big deal – just the mechanics of planets orbiting about the sun in roughly the same flat plane called the ecliptic. Some are closer to us like Mercury and Venus; others like Saturn are farther away, but they regularly bunch up and appear close to one another when they appear in the same line of sight.

Mercury, Comet Elenin, the sun and the moon all lie at very different distances but appear along the the same line of sight Monday.

On September 26 about 11 p.m. Central time, Comet Elenin will be in conjunction with the sun. Since comet and sun are continually moving, a conjunction lasts only a moment, though in terms of proximity, they’ll be near one another for a few days. After conjunction, the comet moves west of the sun and will appear in the morning sky. Keep your fingers crossed something’s left to see.

Many had hoped Comet Elenin would show up in images taken with the Solar and Heliospheric Observatory’s (SOHO) C3 coronagraph, a device with blocks the glare of the sun to show the nearby solar environment. Nope, not there. See for yourself in the picture I grabbed today. That means the comet is certainly below the SOHO magnitude limit of 7 and undoubtedly MUCH fainter. Some amateur astronomers had hoped that backlighting of Comet Elenin’s dust would cause a re-brightening as it approached the sun the same way your breath lights up on a winter day. If that’s happening, it’s still too dim for SOHO to see.

Here's a sidelong view of Comet Elenin, Earth and the sun on September 26. Notice the comet's not in line with the sun but almost 2 million miles above Earth's orbit and some two-fifths the way from Earth to sun. Please note that the view is not to scale and intended to illustrate Elenin's conjunction from a different angle.

The comet is completely invisible down here on Earth because of glare from sunlight now through the end of the month. By about the 10th of October, it may be visible through large telescopes in a dark sky in Leo the Lion shortly before the start of morning twilight. I’ll put together a map soon on how to find it for those who like a challenge. Meanwhile, what’s left of the comet might still show – though I doubt it – in SOHO images through September 29.

Crescent moon and Comet Honda lure us out at dawn

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The crescent moon at sunrise Friday morning from Bishop, California. Credit: Andrew Kirk

Andrew Kirk’s beautiful image of the crescent moon reminds us to watch for an even thinner crescent at the start of morning twilight tomorrow. You’ll find it still in a dark sky by looking to the east an hour and half before sunrise in the constellation Leo below the star Regulus.

The lunar crescent, Comet Honda and Regulus are nearly lined up tomorrow morning low in the eastern sky. Created with Stellarium.

Almost midway between Regulus and the moon, comet 45P/Honda-Mrkos-Pajdusakova will be visible from dark sky sites with 50mm and larger binoculars as a small, dim 7th magnitude hazy patch of light. Telescopes will show it more clearly and may reveal its narrow westward-pointing tail. I’ve been trying to get out for a view, but mornings have been cloudy here. Let us know if you have success in spotting it.

OK, you try holding still for 30 seconds! A portrait of the group last night lit by a dim flashlight. (Astro B. on far right) Photo: Bob King

Last night, I had a wonderful time co-teaching a night photography class to a great group of people not worried about a little frost or put off by half  an hour of clouds before the sky finally cleared. Many took their very first time exposures of stars. As I looked at the glowing replays on their camera backs, it was a thrill to see their cool star trail and Milky Way photos. Nice work everyone!

UARS satellite bites the dust plus a must-see video

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Just for giggles. Be sure to watch to the end :)

The defunct UARS satellite has finally bitten the dust. It broke up late last night September 23-24 over the North Pacific Ocean. Here’s the latest update from NASA as of this afternoon:

NASAʼs Upper Atmosphere Research Satellite reentered the atmosphere sometime between 10:23 p.m. and 12:09 a.m. CDT on 23-24 September. During this period the satellite passed over Canada, Africa and the Pacific, Atlantic and Indian Oceans. The mid-point of that groundtrack and a possible reentry location is 31 N latitude and 219 E longitude (green circle marker on the above map). Credit: JSOC

“NASA’s decommissioned Upper Atmosphere Research Satellite fell back to Earth between 10:23 p.m. CDT Friday, Sept. 23 and 12:09 a.m. CDT Sept. 24. The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite entered the atmosphere over the North Pacific Ocean, off the west coast of the United States. The precise re-entry time and location of any debris impacts are still being determined. NASA is not aware of any reports of injury or property damage.”

Further updates can be found HERE.

Comet Elenin a no-show; Doomed satellite may fall tonight

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A red maple stands illuminates the scene yesterday on the Superior Hiking Trail near Beaver Bay. Photo: Bob King

Happy equinox! Fall began in the northern hemisphere at 4:05 a.m. today when most of us were asleep. At the same moment, the first kiss of spring greeted those living in the southern hemisphere. Yesterday I hiked up north near the Beaver River and stopped often to admire the many fine red and sugar maples aglow with shades of red, scarlet and purple. With yellows provided by the turning birches, the forest was a canvas of color on an otherwise drab, gray day.

Like the descending leaves, today’s the day the 6.3 ton UARS research satellite drops to Earth by way of fiery atmospheric journey. As of 9:30 a.m., its orbit brings it to within 100 miles of the ground with re-entry expected between about 10 p.m. and 1 a.m. tonight Central time (updated as of 6:30 p.m. CDT). It now appears that there’s at least a small possibility it will burn up where people might see it. UARS passes over Europe and North America several times during this period but most of its time will be spent over ocean and sparsely populated lands. The atmospheric heating and breakup of the satellite will begin when it drops to about 60 miles high and finish off at about 30 miles. For a list of overflight re-entry possibilities, please see the list of cities at the end of this blog. All times are courtesy of Robert Matson, Senior Scientist with the Science Applications International Corp. (SAIC). Get more updates HERE or HERE.


Satellite re-entry can be a spectacular sight. This is what the Japanese Hayabusa spacecraft looked like when it burned up in the atmosphere in June 2010 while (safely) delivering a small capsule containing a sample from an asteroid. The video was taken from a DC-8 airborne observatory.

On the first day of fall and spring, the Earth's axis is "sideways" to the sun allowing both hemispheres to receive equal illumination. As we move toward winter, the northern hemisphere tips away from the sun, causing it to drop in the sky which makes for short days and long nights. In summer, the opposite happens. Between those extremes are fall and spring. Notice that the axis tip doesn't change - only our planet's orientation to the sun during its yearly orbit. Credit: Tao'olunga with my own additions

On the first day of autumn, the sun rises due east and sets due west everywhere on Earth. If you’d like to learn the directions around your home, now’s the time. Face the sunset direction and east is directly behind you. Stick out your left arm and it points due south; stick out your right arm and it points due north.While knowing directions sounds like a simple thing, it’s important when it comes to using a star map to find constellations, planets and comets in the night sky. Once you know your home “grid”, you’re good to go.

One of the reasons I enjoy the change of seasons so much is because we really get to feel how the tip of our planet’s axis makes such a difference in our lives. Think of all the fun, gloom, poetry, sweat and diversity of life that arise from this simple fact of nature.

The sun is the little white circle behind an occulting disk that blocks its light so astromers can photograph its outer atmosphere called the corona (streaming rays in picture). Stars Beta and Eta in Virgo are labeled. Comet Elenin is so far a no-show in this 8:30 a.m. photo. Credit: NASA/ESA

Today is also an important day for Comet Elenin. Will it appear in the SOHO coronagraph images? I’m afraid the latest images don’t offer much hope. Using SkyMap software, I plotted the position of the comet on a SOHO photo taken at 8:30 a.m. Central time this morning. Key stars and the planet Mercury are shown along with the empty circle where Comet Elenin should be. I can’t see anything, can you? I’ll post an updated photo later today just in case, but it sure looks like the comet is too faint and diffuse to show. This doesn’t necessarily mean it’s completely gone, only that the breakup has caused it to fade so much that SOHO can’t see it. ** Update: still no comet visible as late as the 2:30 p.m. CDT coronagraph photo.

UARS re-entry times and locations: Times shows are UT or Universal time. To convert to Central time, subtract 5 hours; 4 hours for Eastern, 6 for Mountain and 7 for Pacific. Satellite elevation is shown for each area.

September 24, 2011 (UT) — evening/early morning of September 23-24

00:05-00:06 Scotland  157 km
00:08 Denmark  157 km
00:08-00:10 Poland  157 km
00:10-00:12 Ukraine  156 km
00:14-00:15 NE Turkey  154 km
00:15-00:18 Iran  154-152 km
00:19-00:20 East Oman  152 km
01:16-01:18 Mexico  148 km
01:18-01:20 Texas  148 km
01:20-01:21 Arkansas  149 km
01:21 SE Missouri  149 km
01:22 Illinois  150 km
01:22:30  NW Indiana  150 km
01:23  Michigan  151 km
01:24  Ontario, Canada  152 km
01:25-01:28  Quebec  152-154 km
01:36 Ireland  155 km
01:37 England  155 km
01:37:30-01:38:30 NE France  154 km
01:39 S. Germany/W. Austria  154 km
01:39:30 NE Italy  154 km
01:40-01:41 Slovenia/Croatia/Bosnia/Herzegovina  153 km
01:42 Greece
01:43 Off east-coast of Crete  152 km
01:45-01:46 NE Egypt  151 km
01:46-01:49 Red Sea  149 km
01:49-01:50 Yemen  149 km
01:50-01:53 Somalia  149 km
02:32 Tahiti  148 km
02:47-02:48 Southern California  144 km
02:48 Southernmost tip of Nevada  144 km
02:48-02:50 Utah  145 km
02:50-02:51 Wyoming  146 km
02:51:30 NW South Dakota  147 km
02:52 North Dakota  147 km
02:53 NW Minnesota  147 km
02:53-02:55 Ontario, Canada
02:56-02:58 Quebic  150 km
03:08-03:09 Spain  149 km
03:10-03:12 NE Algeria  148 km
03:12-03:14:30 Western Libya  147 km
03:15-03:18 Chad  146 km
03:18-03:20 Border of Sudan/Central African Republic  147 km
03:20-03:21 Democratic Republic of the Congo  147 km
03:22 Rwanda/Burundi  148 km
03:22-03:24:30 Tanzania  149 km
03:24:30-03:26 Somalia  151 km
03:28 Southern tip of Madagascar  154 km
04:00 Just south of Somoa  146 km
04:18:30-04:20 Washington state  140 km
04:20-04:24:30 Western Canada  141-143 km
04:26-04:28 Quebec  143 km
04:40 Southern Morocco/N. Western Sahara  138 km
04:40:30-04:42 Mauritania  138 km
04:42-04:44 Mali  137 km
04:44-04:45 Burkino Faso  137 km
04:45-04:46 Benin  137 km
04:51-04:53 Angola  140 km
04:53-04:54 NE Namibia  141-142 km
04:54-04:55:30 Botswana  143 km
04:55:30-04:57:30 South Africa  143-145 km
05:19 NW corner of Tasmania  146 km
05:20 SE-most Australian coast  144 km
05:26 NW edge of New Caledonia  137 km
05:27 Vanuatu  136 km
05:49-05:54 British Columbia/Alberta/Saskatchewan/Manitoba  139-141 km
05:56-05:59 Quebec  140 km
06:00 Newfoundland  139 km

UARS satellite to miss U.S. – Groove on the new Vesta flyover video

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Check out this fantastic auroral landscape movie made by the astronauts aboard the space station during a geomagnetic storm on Sept. 17 . They were flying over the southern hemisphere at the time. Notice that Orion rises upside-down from the horizon ahead.

As of 6 a.m. CDT today re-entry of the Upper Atmosphere Research Satellite (UARS) is expected sometime late tomorrow afternoon Central time. The satellite will not be passing over North America during that time period. While the exact location may change, it now appears that UARS will be coming down over the South Pacific north of New Guinea. Let’s hope someone will have a camera or cellphone handy to photograph the fireball, which scientists predict will be bright enough to see in daylight. Latest update HERE.


An 2-minute flyover video taken by the Dawn spacecraft in orbit about the 330-mile diameter main belt asteroid Vesta. Part of Vesta is in shadow because it’s winter in the asteroid’s northern hemisphere and the north polar region is tipped away from the sun.

A series of radiating grooves that remind this writer of a sunflower are visible in this recent photo of Vesta taken by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

This past week the Dawn probe returned new images and a flyover video of the asteroid Vesta. They reveal a wonderland of craters of all sizes, cliffs, grooves and mountains, including the 9-mile-high peak near the south pole, one of the highest elevations in the solar system. Of special interest are the parallel grooves that show so clearly in the movie. They could be faults or fractures related to the giant impact that excavated the large basin in the asteroid’s south polar region. Similar troughs are seen on Mars’ moon Phobos and the asteroid 951 Gaspra. Once-upon-a-time it was a wild, woolly world out there when impacts between asteroid-sized objects were much more common.

To locate Vesta, start with the Summer Triangle. Capricornus is about two outstretched fists below Altair.

You can still see Vesta in binoculars these early fall nights in the southern sky in the constellation Capricornus the Sea Goat. Go out at nightfall and look high in the south for the three bright stars – Deneb, Vega and Altair – that form the Summer Triangle. A line shot from Vega through Altair and extended toward the horizon will take you to the western side of a fainter triangle of stars that comprise Capricornus.

At the bottom of the sloppy Capricornus triangle, are two rather faint stars -  Omega Capricorni and Psi (pronounced ‘sye’) Capricorni. From Duluth, Minnesota’s latitude, they’re about 15 degrees or a “fist and a half” high in the south.

Vesta is easy to find in binoculars in early fall. Watch for it to pass very close to Psi Capricorni the first week of October. Stars shown to 8th magnitude. Maps created with Stellarium

Point your binoculars at these two and use the more detailed map to hop to Vesta. The asteroid is currently 7th magnitude and very easy to see in most binoculars. Half the fun is watching Vesta track eastward in Capricornus over the coming weeks. Even though it looks no different from a star, its movement betrays itself as otherwise.