The ghost of Comet Elenin haunts the morning sky

Comet Elenin is a very faint, elongated streak as photographed through a 4-inch refracting telescope early this morning from the GRAS network in New Mexico. The picture covers about 2 degrees from side to side. Credit: Rolando Ligustri

For those of you who checked yesterday’s blog, you already know that the German ROSAT (Roentgen X-ray satellite) burned up in the atmosphere last night between 8:45 and 9:15 p.m. CDT. To the best of my knowledge, after digging around various websites, it appears to have come down over the Indian Ocean north of the coral atoll Diego Garcia. Too bad there’s so much water on this planet otherwise we’d have lots more satellite parts and meteorites in our collections.

I wanted to share the most recent pictures of Comet Elenin with you. Amateur astronomers have been busy the past few mornings losing sleep photographing and trying to see the comet through their telescopes. The moon is out of the way and Elenin is presently high up in a dark sky after about 3 a.m. These are the conditions we’ve been waiting for for months! And finally, enough pictures have been taken to confirm that the comet is really there.

Another view of Comet Elenin taken this morning with a 10-inch wide-field telescope in Austria. Credit: Michael Jäger

The photos show a faint, elongated cloud of spreading comet dust, the last gasp of what was to be fall’s best bet for a bright comet. Its ghostly appearance hints at how difficult it’s been to see with one’s own eyes in a telescope. To date, only one observer – Juan Jose Gonzalez – has spotted this wispy remnant from his mountaintop observing site in northern Spain using an 8-inch telescope. Jacob Cerny of the Czech Republic is the second person to observe it, but it was so challenging, he listed his observation as “uncertain”.

Take a look at Elenin’s morphology or form. It reminds me of the Headless Horseman from The Legend of Sleepy Hollow. Indeed, the head of the comet is no longer a separate entity as it was before the August breakup. All is one galloping streak of light.

Comet Elenin will continue along its orbit as it slowly moves farther from Earth with each passing day, fading and expanding as it does and likely to never return. Even though this demure object has been wrongly credited with causing earthquakes and other mayhem, the bright side has been a lively discussion of comets and other topics astronomical. These are good things.

Several readers have mentioned or made reference to Arcturus in recent days. I thought it would be an opportune time to give the star – the 4th brightest in the sky after Sirius, Canopus and Alpha Centauri – one last evening farewell before we get up 11 hours later at dawn to welcome it back. What?

Use the handle of the Dipper to "arc" your way to Arcturus during the early evening. This map shows the sky facing northwest around 7:30 p.m. local time. Maps created with Stellarium

Arcturus, an orange giant star with a distinctive warm tint, hovers low in the northwestern sky off the handle of the Big Dipper on late October evenings. It’s best to catch it an hour or so after sunset during evening twilight when the star is high enough to see relatively easily. As dusk melts into darkness, try looking two outstretched “fists” directly above Arcturus for the little horseshoe-shaped constellation Corona Borealis the Northern Crown.

If you have an open view to the northeast during early dawn, you can watch Arcturus return to view - truly, a star for all seasons! This map shows the sky facing northeast around 6:15 a.m. tomorrow morning.

Arcturus makes its first evening appearance in late winter in the northeastern sky. By May and June, it’s high in the south at twilight’s end; its warm light has come to be associated with warming temperatures and the arrival of summer. In fall, the star drops off into the northwest and finally sets, but because nights are better than 12 hours long in late October, Earth’s rotation carries it back into view for observers in mid-northern latitudes. Watch for its winking red light in the northeast at dawn. In a sense, we never lose Arcturus.

The star’s northern location on the celestial sphere is also responsible for its continuous visibility. The closer a star is to the North Star – the pivot-point star due north that remains in one spot in the sky – the longer it remains visible. All stars within a circle with a radius the same as your latitude never set at all. They’re called circumpolar stars because they circle around the North Star day and night without ever touching the horizon. While Arcturus is not quite circumpolar for Duluth, Minn., the fortuitous combination of northerly location and long nights allow it to be seen every month of the year.

Dat’s dee vay dee kookie krumbles – ROSAT coming down tonight

The German ROSAT X-ray observatory was used by scientists in the 1990s to study X-ray emitting objects in the sky.Credit: AP

Sometime later today or early tomorrow morning, the German ROSAT X-ray satellite is expected to plunge into the atmosphere as it makes its final orbit around the Earth. According to the U.S. Strategic Command, it will happen at 9:34 p.m. Central time (2:34 GMT) this evening with an accuracy of +/- 7 hours.

Since its orbit takes it over a vast span of planet Earth between the latitudes of 53 degrees north and south, no one knows yet where it will land. What we do know is that 3,750 lbs. in some 30 pieces will survive the heat and pressure of re-entry and strike water or ground when the moment finally comes. If by chance you’re in position to catch the fall, the crumbling ROSAT will make for a series of spectacular fireballs. I’ll keep you updated through the day as times and fall locations are refined.

** UPDATE 4:15 p.m. CDT — Fall at 9:31 p.m. Central time +/- 3 hours
** UPDATE 8:15 p.m. CDT — Fall at 9:04 p.m. Central time + / – 2 hours
** UPDATE 10 p.m. CDT — Just a few minutes ago, officials at the German Aerospace Center confirmed that ROSAT re-entered the atmosphere between 8:45 and 9:15 p.m. CDT. Not known yet if pieces reached the Earth’s surface.

Early Orionid report, surprise aurora and a possible photo of Comet Elenin

No aurora was in the forecast but it showed up anyway. These four photos were taken around 11:30 p.m. last night and show subtly changing green and pink rays along the northern horizon. The colors are from excitation of oxygen molecules in the atmosphere. Photos: Bob King

Even if my camera didn’t, I saw some splendid Orionid meteors early this morning. The shower is expected to peak tomorrow morning Saturday, so get out if you can. My viewing time was from 1:25 to about 2:30 a.m. Not optimal, but good enough for a few oohs and aahs. Seven Orionids blew by at very high speed and left briefing glowing trails of light called trains. Three sporadic or unrelated meteors were also seen.

Trains shine by the light of vaporizing meteoroid particles and ionized air. As a meteoroid from space shoots through the atmosphere it imparts energy to the air around it. Air molecules react by spitting out electrons in a process called ionization. When the electrons are recaptured a moment later and return to their former places within the atoms, tiny flashes of light called photons are released. When millions of atoms do it, we see a “tube” or trail of glowing air called a meteor.

Scientists use meteor ionization trails to relay information about snow depth, humidity, wind speed and other climate data from the SNOTEL sensors to receiving stations. Credit: USDA

These ionization trails, as they’re called, make excellent mirrors for reflecting a broad range of frequencies of radio waves between stations up to 1,400 miles apart. Not only do hams and other short wave radio enthusiasts use them for occasional communications and listening, but the U.S. Department of Agriculture depends upon meteors to relay climate and snow depth data from remote sensors in tough-to-reach mountain locations in the 13 Western states including Alaska. There are more than 600 sensors in the SNOTEL (snow telemetry) network. They send climate information to receiving stations in Boise,Idaho and Ogden, Utah by bouncing VHF signals off meteor trains 50-75 miles overhead. Pretty cool, eh?

We were treated to an unexpected display of northern lights during the meteor shower late last night and early this morning. It was truly a joy to watch the slow play of rays along the northern horizon shortly before midnight. Like Santa Claus, the aurora often comes by when you’re asleep. Glad I was awake for this one.

A time exposure photo made with a 4-inch wide-field refracting telescope early this morning shows a promising candidate for the Comet Elenin dust cloud. Click the image to take you to the Remanzacco Observatory website, where you can watch a brief video of the sighting. Credit: Ernesto Guido, Giovanni Sostero and Nick Howes

Since the night was so clear and the moon didn’t rise until 1 a.m., I hauled out the big 15-inch scope for another try at Comet Elenin, now located near the bright star Pollux in Gemini the Twins.

Conditions were absolutely perfect with high transparency and steady seeing. I studied the area where the comet was supposed to be for 25 minutes but didn’t  see a thing. Usually I’ll find a “suspect” or faint patch of light that teases the eye but never fully reveals itself. I regret to say that no suspicious characters revealed themselves.

I’ll try again in a couple mornings and then it’ll be time to move on. It appears that the comet, if not completely vaporized, is so faint that only large, wide-field telescopes using long time exposure photography might still show it.

Just as I write this, a report came in about a possible sighting of the comet by Ernesto Guido from the Remanzacco Observatory in Italy. He and his team photographed Comet Elenin remotely using a telescope at the GRAS network in New Mexico this morning. Check out the photo – it sure looks like a convincing candidate. More to come.

Comet storm pummels alien solar system in Corvus the Crow

A fall scene featuring our nearest extraterrestrial neighbor and a few hardy poplar leaves. Photo: Bob King

The last quarter moon was a beautiful sight early this morning nestled among the few leafy tree tops left in the neighborhood. If you’re out around 8 a.m. and have a telescope or pair of binoculars, the moon is high enough and the sky dark blue enough for craters to show easily. I know it sounds incongruous but have a look for yourself. The waning moon “rides high” in the early morning hours and makes an inviting target if you’re up for school or work.

The waning crescent moon passes near Mars and Regulus in Leo the next two mornings. Created with Stellarium

The peak of the Orionid meteor shower begins tomorrow morning (Friday) and continues through Saturday morning. If you plan on watching it, be sure to also check out the planet Mars near the moon and Leo’s brightest star Regulus. The Red Planet is slowly moving eastward in Regulus’ direction en route to a fine conjunction with the star on November 10. The moon, being much closer the Earth, moves more quickly, exiting the scene in just a few days.

This artist's conception illustrates a storm of comets around Eta Corvi (left). The Spitzer Space Telescope's infrared detectors picked up indications that one or more comets was recently torn to shreds after colliding with a rocky body. One such giant comet is shown smashing into a rocky planet, flinging ice- and carbon-rich dust into space, while also smashing water and organics into the surface of the planet. A glowing red flash captures the moment of impact on the planet. Credit: NASA/ JPL-CalTech

Just after wrapping up yesterday’s blog, I got a NASA news release about a very cool discovery of a cloud of (probable) comets centered on the naked eye star Eta Corvi (AY-tuh KOR-vee) in the constellation Corvus the Crow. Coincidentally, one of my students asked me the night before whether reservoirs of comets had ever been seen around stars other than the sun. Ask and you shall receive.

While disks of dust and rubble – solar systems in the making – have been photographed around stars like Fomalhaut, Vega, Beta Pictoris,  I wasn’t aware of any “comet clouds” like our solar system’s Oort Cloud. This hypothesized spherical stockpile of comets is thought to lie 50,000 Earth-sun distances or nearly one light year from the sun in all directions. Astronomers believe that long period comets like Comet Halley and Comet Hale-Bopp originated in this remote region.

The star Eta Corvi is visible with the naked in the small, trapezoid-shaped constellation of Corvus the Crow. Right now Corvus is in the daytime sky near the sun (upper left) and Saturn.

So how amazing it was to learn of another star buzzing with it own cloud of icy bodies. NASA’s Spitzer Space Telescope, which studies the sky in the light of heat energy or infrared, found evidence of heated dust and debris from a comet hailstorm around the star Eta Corvi.

“Spitzer has spotted a band of dust around Eta Corvi that strongly matches the contents of an obliterated giant comet, probably destroyed by a collision with a planet or some other large body. The dust is located close enough to Eta Corvi that Earth-like worlds could exist in the collision zone, suggesting that planets like our own might be involved. The Eta Corvi system is approximately one billion years old, which researchers think is about the right age for such a hailstorm,” according to the NASA release.

Some four billion years ago, Earth and the inner planets were in the same situation. As Jupiter and Saturn were migrating toward their present day orbits in the outer solar system, they gravitationally disturbed millions of icy comets that lay beyond Neptune. Some were cast into the Oort Cloud while others were booted into the inner solar system, where they bombarded the Earth in what’s known as the Late Heavy Bombardment (LHB).

It was during the LHB that astronomers believe the Earth garnered its water and a fair share of carbon-containing materials, both of which are found in comets. Abruptly at 3.8 billion years ago, the bombardment ended, and the neighborhood has been relatively quiet since. It now appears that we might be seeing the same around another star – a real first and a timely answer to a student’s question!

Orionid meteor shower could make your wildest dreams come true

Meteors, nicknamed "falling stars", appear as bright streaks of light against the steady stars. Photo: Bob King

I’ve always enjoyed the scene in the movie Napoleon Dynamite when Pedro, Napoleon’s friend, runs for school president under the slogan “Vote for me, and I’ll make all your wildest dreams come true.”

Since we’ve all wished upon a shooting star at one time or another, the Orionid meteor shower will offer some 20 wishing possibilities per hour when they peak this Friday and Saturday mornings (Oct. 21 and 22) in the hours after midnight. They’re called Orionids because the meteors appear to originate from a spot in the sky to the upper left of the bright pink star Betelegeuse in the constellation Orion the Hunter.

The Orionid meteors will all point back to a spot just above the bright star Betelgeuse in Orion called the meteor radiant. You might also see some stray meteors called sporadics that appear on any given night. Orionids can all be traced back to the radiant. Created with Stellarium

Orionids made their first appearance earlier this month as Earth began entering the dust stream left behind by the one and only Halley’s Comet. We cross its orbital path twice a year, and each time we do, our planet slams into sand-sized bits of debris strewn by the comet during the many times it’s circled the sun. The other Halley-related shower is the Delta Aquarids on April 21.

Each year in late October Earth travels through a stream of dusty debris left behind by Halley's Comet. Illustration: Bob King

Since we encounter these cometary morsels nearly head on, they strike the atmosphere at over 147,000 miles per hour and vaporize in bright streaks of meteoric light. The Orionids have been a very reliable and active shower in recent years. Weather permitting, I always make the effort to get out for a look, since meteors are guaranteed. They’re typically white, modest in brightness and amazingly fast. Expect occasional fireballs from the shower, too.

Meteors appear to radiate from a point in the distance the same way snow striking your car windshield does when driving. Even though the snowflakes and meteors are generally parallel to each other, our eyes see them as converging in the distance. A similar illusion happens when looking down a set of train rails. Photo: Bob King

The best time to see them is now through the end of the week but in particular on Friday and Saturday mornings. While Orion’s up in the southeast by midnight, you’ll do better to set the alarm and step outside around 4-5 a.m. With the constellation and radiant high in the south at that hour, many more meteors will be visible. Find a place without a lot of glaring lights, set up a chair and prepare something warm to drink to ward off the fall chill and keep you alert.

The best direction to face is south with Orion in full view. Since dawn starts around 6 a.m. where I live, my plan is to out at 5 for a nice hour’s worth of darkness. The only ding in an otherwise ideal morning will be the thick crescent moon off to the east near the planet Mars. Its light will hide some of the fainter meteors, but shouldn’t pose a serious threat to your wishing and watching enjoyment.

Mysterious gamma ray sources may unlock dark matter’s secrets

Part of the all-sky Fermi Gamma Ray Observatory map. The thick yellow-orange streak is the plane of the Milky Way galaxy where many gamma ray sources are concentrated. The Crab Nebula - the remains of a supernova explosion in 1054 A.D. - is the bright source at right., and an unknown source is circled at left. Credit: NASA/DOE/Fermi/LAT Collaboration

The other day we dropped in on the doomed German ROSAT telescope, which is still slowly grinding its way through the upper atmosphere en route to nemesis. Scientists used the orbiting observatory in the 1990s to study high energy sources like colliding galaxies and black holes. Best predictions at the moment call for it to re-enter and burn up in the atmosphere October 23 early Sunday morning Central time. It’s still too early to say exactly when and where.

If sitting in the dentist chair while getting your teeth X-rayed makes you wonder just what’s going on in your mouth, you’ll be happy to know the electromagnetic spectrum, which includes light, UV and radio waves, doesn’t end there. No, no, no.  The most energetic form of light is gamma radiation or simply gamma rays. While too much X-ray exposure can lead to sickness, gamma rays are off the charts. They’re spawned in extremely explosive events like H-bombs or when matter screams down the maw of a black hole. Don’t get too close. Gamma rays are so powerful they’ll literally tear into your cell membranes and rip apart your DNA.

OK, enough of the scary stuff. A gamma ray telescope is clearly the tool of choice for scientists who want to learn more about what powers the most energetic and catastrophic happenings in the universe. Fortunately for all of life, except maybe the toughest bacteria, gamma rays are blocked by Earth’s atmosphere. NASA, with the help of other countries, built and launched the Fermi Gamma Ray Space Telescope into low-Earth orbit 2008 to surmount this little problem.

In its second survey of the sky, Fermi found 1873 gamma ray emitting objects or sources. The majority are giant black holes in the centers of galaxies that beam radiation into space as they gobble up gas and stars that stray too close. Others are superdense stars the size of cities called neutron stars that beam gamma rays into space as they spin like whirling dervishes. Neutron stars are created when a once-giant star collapses and explodes in a supernova explosion leaving only its tiny, dense core.

An electron (bottom) meets a positron (top) and annihilate in pure energy. Credit: NASA

600 of Fermi’s finds however are complete mysteries. Some could be radiation shot off from colliding galaxies, but intriguingly, the sources might also be the sign of dark matter. Some scientists believe when two dark matter antiparticles bump into each other, they annihilate in a flash of gamma ray energy.

Antiparticles look and behave like normal electrons, protons and neutrons found in the atom but they have an opposite electric charge. Electrons are negatively charged, but an anti-electron, better known as a positron, is in every way its twin but positively charged. These strange siblings are as real as the hair on your head (if you still have hair). Put a particle and an antiparticle together and they’ll annihilate instantly in a burst of energy. If I’m not mistaken, this was the technology that powered the engines of the fictional star ship Enterprise in the Star Trek TV series.

The video, just released by NASA, explains the Fermi results and delves a bit more deeply into the puzzle of the gamma ray unknowns. I hope you’ll enjoy watching it. Whatever the new sources ultimately prove to be, scientists are certain to take the bait, opening a niche of new knowledge in the process.

Smiles all around as meteorite hits comet

One of the newest extraterrestrial visitors to land on Earth (at left), an 88 gram meteorite that fell near Paris late this summer. The photo at right shows meteorite collector Alain Carion with Mr. Mosset and Miss Comette. Credit: Alain Carion

OK,  now that I’ve drawn you in to this story, here’s the truth. The meteorite didn’t hit exactly hit a comet but rather a ‘Comette’ as in the roof of a home owned by Madmoiselle Comette (pronounced the same) and her companion Monsieur Mosset in Draveil, a suburb of Paris. No one’s quite sure when the meteorite punctured the roof, but it may have happened in August while the couple was on vacation away from the city.

In early September their roof was leaking after a thunderstorm, so they called a roofer to make the repair. While replacing the roofing tiles, he discovered a curious black stone with a pale gray interior and presented it to the owners. Suspecting it might be a meteorite, Mosset later took the stone to the French meteorite collector Alain Carion who owns the Minerals-Fossils-Meteorites shop along the banks of the Seine River in Paris. Carion’s face must have lit up in a big smile, because it was clear to him that the 88g (3 ounces) specimen was indeed a rock from space.

A 5.3 kilogram (11.6 lbs.) new specimen of the Draveil meteorite. Credit: Alain Carion/

In his own words: “Mr. Mosset did show me a splendid extra-terrestrial rock of 88 grams, with all the right features: black fusion crust, regmaglypts , pale matrix inside with traces of iron and troilite, attracted to a magnet. Perfect! We had here a real meteorite, and fallen just outside Paris.” Just an FYI, regmaglypts are those thumbprint shaped depressions seen in some meteorites. They’re places where the heat of entering Earth’s atmosphere has melted out softer materials in the stone.

To the delight of everyone, two additional pieces weighing around 2 and 5.3 kilograms  of the meteorite fall have recently been found. Since no known meteorite has ever fallen so near Paris, meteorite collectors around the world are very excited about the possibility of adding a small fragment of history to their collections. From outward appearances, the meteorite looks like an what’s known as an ordinary chondrite. Chondrites are extremely ancient – 4.5 billion years old – and thought to originate in the crusts of asteroids in the asteroid belt. Collisions between asteroids liberate fragments which eventually find their way to Earth and lovely places like Paris.

This week the International Space Station (ISS) begins making passes over the region during the early evening hours. Here are times when you can see it fly over the Duluth, Minn. region. For times for your town, head over to Spaceweather’s Satellite flybys and ener your zip code or log on to Heavens Above. The ISS will appear as a brilliant star moving from west to east. And who knows. Maybe a meteorite will hit your roof too while you’re out with your head in the sky.

* Tonight October 17 starting at 7:52 p.m. Brilliant pass across the southern sky. Disappears into Earth’s shadow just east of Altair near the bottom of the Summer Triangle. * Tuesday October 18 at 6:54 p.m. low in the south and southeast.
* Wednesday October 19 at 7:31 p.m. About as bright as they come. High pass in the southern sky and brighter than Jupiter.
* Thursday October 20 you get two for the price of one. First pass at 6:33 p.m. across the south; 2nd brief pass in the northwest at 8:08 p.m.
* Friday October 21 at 7:10 p.m. Brilliant as it travels nearly directly overhead

Creepy crawlies aboard mission to Mars’ moon Phobos

Phobos, the destination of the Russian Phobos-Grunt mission, is seen here in orbit about Mars through the eyes of the Mars Express orbiter. The moon is only 14 miles across and orbits the planet in just over 11 hours or twice during each Martian day of 24 hours 37 minutes. Click to enlarge. Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA

The Russians will soon return to Mars with the launch of the Phobos-Grunt probe on or around November 8. Russia hasn’t had a successful interplanetary mission in decades. The last attempt was the Mars 96 probe launched in 1996 which quickly ended when a rocket engine failed while still in Earth orbit. We hope all goes well on this multifaceted and imaginative mission.

The Phobos-Grunt probe being prepared for vacuum chamber testing. Credit: NITs RKP

Phobos-Grunt (‘grunt’ is Russian for ‘soil’ or ‘dirt’) is an unmanned mission of the Russian Federal Space Agency that will land on the Martian moon Phobos and return a soil sample to Earth. This is the first-ever attempt to sample a planetary moon. Assuming a successful liftoff, the probe will reach Mars next October and dispatch the Yinghuo-1 Chinese satellite to orbit and study the planet’s surface. Over the next several months, Phobos-Grunt will study Mars, the Martian moons and search for a safe landing spot as it slowly pulls up alongside Phobos. Touchdown is scheduled for sometime in February 2013.

15 instruments will study the little moon and a robotic arm and drill will gather up soil samples.  Liftoff  from the moon happens in early 2014. The return capsule, expected to arrive back on Earth later that August, will contain 200 grams (just under 1/2 lb.) of soil and include a life science experiment of The Planetary Society, called Living Interplanetary Flight Experiment, or LIFE.

Tardigrades are found everywhere on Earth and have survival skills that would put humans to shame. A sample of them is headed for a round-trip journey to Mars moon Phobos.

The special ‘bio-module’ will hold representatives from all three major domains of earthly life to find out how well they survived for several years in the extremes of outer space. Among the 10 creatures included will be four types of bacteria, three bacteria-like organisms called archaea that thrive in extreme conditions and three species from the domain of eukaryotes or organisms with more complicated cell structures. You and I belong to this last group. Standing in for us will be a fungus (yeast), seeds from the mouse-ear cress plant and my personal favorite – tardigrades or ‘water bears’. These microscopic animals with 8 legs only grow to about a millimeter and are found all over the planet. They’re able to survive in temperatures ranging from near absolute zero (459 below) to 300 above, can handle far more radiation than most animals and live up to 10 years without water. That’s one tough bug!

Phobos is pocked with craters including one very large one named Stickney (far right edge) that nearly shattered the moon. Credit: NASA

Phobos is a fascinating moon. It’s only 14 miles across and orbits 5,827 miles above the surface of Mars. That’s close enough for its orbital motion to outpace the slower rotation of Mars (24 hours 37 minutes) making the moon rise in the west and set in the east in just 4 hours and 15 minutes as seen from the Martian surface.

Based on its density and how the moon absorbs and reflects sunlight, astronomers have determined it’s composed of a mix of rock and ice with the ice locked somewhere below the surface. Its composition matches a group of dark carbon and water-rich meteorites called carbonaceous (car-bon-NAY-shuss) chondrites (KON-drites). Since similar carbonaceous asteroids are known to inhabit the asteroid belt, it’s believed Phobos as well as the smaller Martian moon Deimos were stray asteroids captured by Mars long ago.

Tears for Comet Elenin, but there’s more to life

Seven sunspot groups dot the sun's face in this photo from 8:30 CDT this morning. Credit: NASA/SDO

Time to catch up on the news. The sun is positively peppered with sunspot groups but they’ve been mostly well-behaved with few flares to shows for so much spottiness. Just the same, there’s a good chance for minor auroras across the northern U.S. and Canada this evening from something else in the sun’s bag of tricks – a coronal hole.

Look low along the northern horizon for a greenish glow during the early evening hours . Views will be compromised after about 9 p.m. when the moon is up high enough to spill light across the sky.

Let’s not forget the supernova in the Pinwheel Galaxy in the Handle of the Big Dipper. At magnitude 11.7, it’s still within easy range of 6-inch and larger telescopes. Amazing to think that the supernova, discovered on August 24, is nearly two months “old” and continues to blaze so brightly. Catch it as early as you can at the end of evening twilight before it drops below the trees and roofs. Maps for finding it are here in this earlier blog.

Photo of Comet Elenin's position on October 9 taken through a 10-inch telescope. Stars (long streaks) as faint as 17th magnitude are visible while the red squares are positions of even fainter asteroids in the field of view. No comet cloud or fragments are visible. Click photo to read and see more Elenin attempts. Credit: Ernesto Guido, Giovanni Sostero and Nick Howes

There’s a discussion going on right now among comet observers about whether Comet Elenin is visible or not. Tomorrow, what’s left of the comet makes its closest approach to Earth at 22 million miles. This was the time we’d all been hoping to see it near naked eye brightness, but it crumbled in August and the remaining icy fragments have all but vaporized away in the sun’s heat.

Comet Garradd photographed last night from Italy by ace astrophotographer Rolando Ligustri. Two tails are visible - a blue ion tail at top and a yellowish dust tail below.

Two positive observations of Elenin were made about a week ago by trustworthy observers under excellent skies, but larger telescopes and long time exposures have shown nothing. Other experienced visual observers have also had no success. Granted, they were all battling low altitude and the glow of the zodiacal light. What the two observers would have seen was the faint, residual dust cloud left in the wake of the breakup. The next opportunity to see Comet Elenin will be in about a week, when it will be much better placed in a dark morning sky. Expect lots of amateur astronomers to be out with scopes and cameras for one last attempt. I’ll have more news then.

To find Comet Garradd with binoculars or telescope, face due west and find the two bright stars on the right side of the Summer Triangle - Altair and Vega. Use them to create another triangle with 2nd magnitude Alpha Ophiuchi directly below. Once there, use the map below to navigate the short distance from Alpha to the comet. Created with Stellarium

Despite Elenin’s poor showing, there’s no need to hang your head. Comet Garradd is still going strong at around magnitude 7.5 during the early evening high in the western sky near the border of the constellations Hercules and Ophiuchus (oh-fee-YOU-cuss). From a dark sky it looks like a small, fuzzy puff in binoculars. Telescopes will show a bright comet head or coma and faint tail pointing east. The moon is now rising late enough to provide the dark sky you’ll need for the best view.

Once you're at Alpha Oph, you can star hop up a chain of 5-6 magnitude stars to get to the comet. Nearby Alpha Herculis is also a helpful guide star. This map shows the sky as you face west. Comet positions are shown every five days. The dashed line is the constellation boundary. Created with Chris Marriott's SkyMap software

Don’t forget to look for the X-ray telescope ROSAT tonight we talked about yesterday. Now that its orbit is dropping lower, the doomed satellite has been reported as bright as 1st magnitude! Scroll down to Friday’s blog for links on how to find it.

This image of the asteroid Vesta, calculated from a shape model and based on photos, shows a low angle view of the south polar region. The mountain in the foreground is 13 miles high. Click to enlarge. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

And finally, I’ll leave you with a couple recent pictures taken by the Dawn spacecraft of a dark-rayed crater and one of the highest mountains in the solar system.These wonders of nature are found 168.5 million miles from your doorstep on the asteroid Vesta.

A fresh 1-mile diameter crater surrounded by dark rays of excavated rock from Vesta's crust. Rays are normally composed of bright material, so more study will be needed to answer why these are dark. Click to enlarge. Credit: NASA

Another one bites the dust – ROSAT satellite coming down soon

Jupiter and the waning gibbous moon shine between fall trees late last night. Photo: Bob King

Darkness comes early in mid-October. For some, the disappearance of daylight is tough to handle. We feel like moles in a dark tunnel from dinnertime until the next morning’s breakfast. Most people seem to be more in tune with daylight instead of darkness, yet many sky watchers have learned to embrace the night. The stars may be dim but getting to know them and the ragtag galaxies, planets and nebulae is like being in a room with a thousand candles. Their light and energy stimulate a reflective and peaceful state of mind as satisfying in its way as streaming rays of sunshine. As daylight trickles away, I hope you’ll also find light and inspiration in the nights ahead.

Artist view of the German X-ray observatory ROSAT in space. Credit: German Aerospace Center

Looks like we’re in for Satellite Crash Act II. The German science observatory ROSAT, short for Roentgen Satellite, make its fiery plunge to Earth sometime between October 22-24 over a broad zone between latitudes 53 degrees north and south. Like the widely-publicized burn-up of NASA’s Upper Atmosphere Research Satellite (UARS), this satellite will also come down uncontrolled. Satellite trackers will only have a general idea of where it might land hours before it does. As with UARS, you shouldn’t be too worried. Since the Earth is 2/3 covered in water and thankfully still  blessed with a lot of uninhabited land, there’s a good chance it will crash without incident just as UARS did over the South Pacific.

When ROSAT finally does come down, it will be traveling at nearly 17,000 mph. The tremendous heat generated by friction with the air will burn up much of it up, but German scientists estimate 30 pieces will survive. Unlike UARS, ROSAT’s made of specially hardened components, so more of it will remain intact during re-entry – 3,750 lbs. of pieces will shower the ground versus an estimated 1,200 lbs for UARS. There’s  a 1 in 2,000 chance a person will be struck by the debris, which breaks down to a 1 in 14 trillion chance any particular individual will be hit.

An X-ray emitting neutron star (upper left) blinks out as the moon passes in front of it in these photos made by ROSAT. High-energy X-rays are shown in yellow, low energy ones in red. The moon scatters X-rays given off by the sun. Credit: ROSAT, MPE, NASA

ROSAT, an orbiting space telescope optimized to study the sky in X-ray light, is named after William Roentgen, the German scientist who discovered X-rays back in 1895. It operated for over 8 years beginning in 1990 before being shut down in 1999. Many high-energy objects in the universe emit X-rays including neutron stars, black holes, galaxy clusters and debris blasted into space by supernovas called supernova remnants. Since Earth’s atmosphere absorbs X-rays, telescopes made to focus this powerfully energetic light need to be lofted into orbit.

ROSAT created a detailed (for its time) map of the X-ray sky, took the first photos of X-rays bouncing off the moon and discovered X-ray emission in comets. It’s since been superseded by the Chandra X-ray Observatory with its much finer resolution.

This composite view of the entire sky in X-rays was made by ROSAT. The red is radiation emitted by hot gas in the halo of the Milky Way, the yellow from nearby gas bubbles at several millions of degrees and the highest energy blue from supernova remnants. Credit: ROSAT

You can still watch ROSAT track across your sky in the coming week before its plummet. Below are times when it’s visible from the Duluth, Minn. region. For times for your neighborhood, log on to Heavens Above and select your city and then click the ROSAT link. You’ll be shown a list of passes. When you click the date link, a nifty map pops up to help you know exactly where to look. You can also enter your zip code at the Spaceweather Flyby link and get times and general directions.

Like the space station, ROSAT travels from west to east across the sky, but it’s not nearly as bright. Expect to see a steady moving “star” of about 2nd magnitude or similar in brightness to those in the Big Dipper. It zips along fairly quickly now that its orbital altitude has been dropping from friction with the upper atmosphere.

* Tonight Oct. 14 beginning at 7:55 p.m. A brief and faint (magnitude 4) appearance low in the northwestern sky in the Big Dipper.
* Saturday Oct. 15 at 7:41 p.m. A better and brighter show tonight at mag. 2 1/2. Appears in the northwest and moves through the Big Dipper before fading away under the North Star.
* Sunday Oct. 16 at 7:25 p.m. Excellent high pass in the north at mag. 2.2
* Monday Oct. 17 at 7:08 p.m. Similar pass to yesterday. Bright at mag. 2.0