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.

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

Did distant comets quench a thirsty Earth?

A striking active prominence issues from the big sunspot group 1305 as it approached the western limb of the sun last Thursday. Prominences are towering flames of incandescent hydrogen gas many thousands of miles long often associated with sunspot groups. Credit: John Chumack

A beautiful, bright sun shines outside my window this morning. It was preceded by the setting moon and the onset of dawn, both of which I saw while hunting for Comet Elenin. In the briefest of intervals, I watched the sky go dark around 5:45 a.m. and then the lights slowly come back up with twilight after six. Try as I might however, I couldn’t convince myself of seeing the comet through the big 15-inch scope. Maybe there was a bit of fuzz there, maybe not. I used low power, medium power and even the power of imagination but nothing I tried convinced me Elenin was there. I’ll be out again around the 23rd or 24th when conditions will be much better. Until then, happy trails Comet E!

Comet Hartley 2 photographed by the Deep Space/EPOXI spacecraft in 2010. Credit: NASA

Last week European astronomers using the Herschel Space Observatory announced they’d found water in Comet Hartley 2 with almost the same composition of water found in the Earth’s oceans. You might remember Hartley 2 which passed near Earth in October 2010 and became faintly visible with the naked eye for a time. It was also the target of a close flyby by the Deep Impact mission a month later.

The question of where our planet got all its water has been hotly debated. The Earth grew over a period of 1-200 million years 4.3-4.5 billion years from the accumulation of millions of meteorites and asteroids. Heat arising from all that impacting material and the decay of radioactive elements (which release heat energy) melted our little globe, causing the heavier metals like iron and nickel to sink to the core with lighter rocks floating to the top to form the planet’s crust. Our world was once a glowing ball of hot magma – not exactly the kind of place you’d find water sloshing about.

That’s why scientists believe the water that’s now so plentiful and makes our world so distinctive had to be ‘delivered’ later after things cooled down. Since comets are composed largely of water ice and there are billions of them – especially in the early solar system when there was so much more ‘junk’ around – they seemed the perfect choice as a delivery mechanism to quench our planet’s thirst.

A neutron (in blue) joins hydrogen's single proton to make deuterium, represented by the chemical formula 2H.

One problem: almost all comets astronomers have studied so far contain twice as much deuterium in the hydrogen that makes the H in their H2O. Deuterium? The most common form of hydrogen has only one proton in its nucleus circled by a single electron, but 1 out of 6,420 hydrogen atoms in the Earth’s oceans also has a neutron paired up with that proton. The addition of the neutron doubles the mass of the hydrogen which is why D2O (D for deuterium) is nicknamed ‘heavy water’. If comets really are responsible for bringing water to Earth, why don’t our oceans have more heavy water? Enter the European Space Agency’s Herschel Space Observatory, the largest space-based scope currently in orbit. Its 138-inch (3.5 meter) diameter mirror and optical system are optimized to study the sky in infrared light.

This illustration shows the orbit of Comet Hartley 2 in relation to those of the five innermost planets. The comet made its latest close pass of Earth in October 2010, at which time Herschel observed the comet. Water shows as a big blue bump in the comet's light spectrum (right). Credits: ESA/AOES Medialab; Herschel/HssO Consortium

Herschel studied Comet Hartley 2 and discovered that its water has almost the same composition – regular vs. heavy water – as the Earth’s oceans. Most of the comets previously studied are thought to have formed closer to Jupiter and Saturn and then booted into the outer solar system’s Kuiper Belt through gravitational interactions with those planets. Comet Hartley 2 is different. Its birthplace was the frigid Kuiper Belt, where the deuterium to hydrogen ratio may have been very different from the one in comets formed closer to the sun.

Beyond the orbit of the most distant planet Neptune lies a vast region populated by icy asteroids and comets called the Kuiper Belt. Comets like Hartley 2 are believed to have formed here 4.5 billion years ago. Later some of them migrated inwards and may have collided with Earth, delivering water to the early planet's parched surface. Credits: ESA/AOES Medialab

So the water that makes our planet the wettest, wildest place in the solar system may still have come from comets, but from ones formed in the far reaches of the solar system. Astronomers using the Herschel scope will now be looking at other comets to confirm their hypothesis.

Comet Elenin sighted in the morning sky

This photo was taken around 5:45 a.m. on Oct. 7 through a 5-inch refracting telescope. The bit of fuzz marked by the line may be Comet Elenin or electronic noise picked up during the exposure. The faintest stars shown are dimmer than 15th magnitude. Credit: Mike Holloway

Amateur astronomers have been busy the past few mornings with telescopes and cameras searching for what’s left of Comet Elenin. I’m aware of at least a half-dozen attempts to see the comet, all but one of which resulted in a negative or uncertain result. Leonid Elenin’s photograph posted in my Oct. 6 blog may possibly show a fragment of the comet.

This morning was the best opportunity to look because the comet was moderately high in the eastern sky (about 23 degrees or “two fists”) during a narrow window of darkness between moonset and twilight. Observing from a mountain location over one mile high near Leon in northern Spain, dedicated comet observer Juan Jose Gonzalez saw Elenin as a faint, diffuse haze of magnitude 10.7 with a short tail pointing northwest. The comet had no central brightening and measured 6 arc minutes across or half the distance between Mizar and its companion star Alcor in the Big Dipper. Gonzalez was using an 8-inch Schmidt-Cassegrain telescope, and seeing conditions were very good at the time.

His is the only positive observation so far. The news gave me a jolt of hope that I and others might still see it. Photographs and other attempts have either shown a tiny 18th magnitude object or a suspected faint patch of light. These earlier observations were made when the comet was lower in the sky and its light more readily absorbed by the thicker, hazier air near the horizon. Gonzalez is an expert observer working under very dark skies. He routinely sees faint comets that escape the attempts of other less experienced amateur astronomers, myself included.

Still, why the disparity between his and Leonid Elenin’s 18th magnitude estimate of the comet’s brightness? Two factors may be at play. Elenin’s was based not only on a photograph, but also when the comet was much lower in the sky. I don’t know the field of view of his photo, but if it’s small – and especially with the comet much lower – it might not show the distended, faint coma but rather a fragment inside. That fragment, if that’s what it is, is obviously very faint. Elenin is still not sure if what he photographed is the comet or just noise.

Meanwhile, Gonzalez observed the comet much higher up with a wider field of view. Although unable to see any fragments – they’re too faint to spot visually – his wider field of view, darker sky (due to higher elevation) and very perceptive eye allowed him to see the entire coma and even a short tail. Based on the details of his observation, the coma would have looked like the faintest puff of light just a little brighter than the sky background. Although 10.7 magnitude is not faint per se, that brightness is spread across 6 arc minutes of diffuse haze, making the comet appear quite dim. Having compared my observations with Gonzalez’s for a number of years now, I’m guessing it would have been very faint from my dark sky site even in my 15″ reflector. No one to my knowledge photographed the comet this morning with a wide-field telescope. Had they, we’d have a better basis for comparison.

Detailed finder map showing Comet Elenin with bright Regulus at lower right, 6th magnitude stars 34,37 and 42 Leonis and fainter stars to 12th magnitude. North is up. 'E' is the comet's position at 5:45 local time for the UK, while 'P' shows the comet's position at 5:45 a.m. for the Pacific time zone. Created with Chris Mariott's SkyMap software

Tomorrow morning (Oct. 10) offers one last opportunity to see the comet before moonlight cuts it to the quick. Since the nearly full moon will set about 15 minutes after the start of twilight, there will be no true darkness, but it may prove just dark enough for the comet to make a very brief appearance before dawn grows too bright. Take heed! Comet Elenin is dim and diffuse and will prove a challenge even for amateurs with larger telescopes and good maps. Use the map above to help you find it. The comet will be about 4 degrees northeast of Regulus.

After tomorrow, a bright moon will make it virtually impossible to see the comet until October 21, when Elenin will once again be sufficiently high in the east to tackle before moonrise. After the 21st, conditions rapidly improve – by the 24th the comet will be high in the southern sky before the start of morning twilight.

Sparks swirl from a bonfire in the backyard. Photo: Bob King

I realize that all this talk about such a dim comet may be overmuch for some of you reading this, but had Elenin not broken to pieces in August, it’s possible we’d be seeing it in binoculars by now. What’s visible now is the dim, expanding dust cloud from the vaporization of icy-dusty cometary fragments. Speaking of which, it sounds like the eastern hemisphere had a fine Draconid meteor shower last night. We were cloudy here in Duluth, Minn. For fun I built a bonfire in the backyard and watched a homemade meteor shower of orange sparks fly to the heavens.

Comet Elenin extremely faint after solar conjunction

What's left of Comet Elenin lies at the intersection of the two yellow lines. Click photo to go to L. Elenin's website. The three bright objects are images of brighter stars. Credit: Leonid Elenin

I haven’t seen it yet but its discoverer, Leonid Elenin, remotely photographed the comet early this morning using a computer-operated telescope in New Mexico. The news is bad for visual observers – Comet Elenin is exceedingly faint, around 18th magnitude. If that’s all that remains of the comet, it will be too faint to spot visually in even large telescopes.

As the comet rapidly moves higher into a darker sky in the next few mornings, a tenuous dust cloud might still show in large amateur scopes, but that’s only a hope. From here on out, time-exposure photos taken through large telescopes may be the only option to keep track of the comet’s debris. In an e-mail communication this morning with Mr. Elenin, he pointed out that because the comet is so faint, more images will be needed to confirm that what’s shown in his photo are its remains.

Note: For today’s blog on Jupiter and choice sights, please scroll down.

Earth to Elenin – Are you still out there?

Comet Elenin on August 3 (left) when near maximum brightness and after breakup when last seen on September 14 (right). Credit: Michael Mattiazzo

This is the week many have looked forward to since shortly after the discovery of C/2010 X1 Elenin last December. Original predictions made last winter based on a relatively close approach to Earth on October 16 indicated the comet might have been as bright as 4th magnitude and visible with the naked eye from outer ring suburbs and rural areas.

Much has changed since then. Comet Elenin was slow to brighten during spring and early summer. Even through my 15-inch reflecting telescope it never amounted to more than a faint 13th magnitude patch of hazy light. By mid-August things looked better when the comet became visible to southern hemisphere sky watchers in binoculars at around magnitude 8. Revised predictions then downgraded its brightness at closest approach to Earth from 4th to 6th magnitude. While very faint to the naked eye, that still easily placed Elenin within binocular range.

So far so good. Then around August 20th the comet busted apart under the intense solar heat experienced en route to perihelion or closest approach to the sun. Comet Elenin’s lost its intense inner glow and suddenly began to fade. It was last seen about September 14 as a diffuse glow fainter than 10th magnitude. Sad news for comet observers.

Use the two stars at the end of the Big Dipper's bucket to point you to the bright star Regulus in Leo the Lion. Using the detailed chart below, you can navigate to Comet Elenin's location. This map shows the sky around 90 minutes before sunrise facing east. Created with Stellarium

Still we hoped the comet might keep its act together long enough to show up in the SOHO coronagraph images late last month. Maybe a brightly glowing cloud of dust? Nothing was seen. Now we’re finally down to the last straw. Will the comet be visible through telescopes when it returns this week in a dark sky before dawn?

I’ve drawn up a couple charts to help you search for it. The wider one includes the Big Dipper to point you to Leo and its bright star Regulus. From there you can use binoculars and telescopes to navigate to Comet Elenin. And don’t forget our consolation prize –  Comet Honda-Mrkos-Pajdusakova! It’s still around 7th magnitude and faintly visible in binoculars, while a telescope will show its skinny tail and bright, pale blue-green coma.

In this detailed map, the star Regulus is at top right. The comets' positions are shown for each day beginning October 4. Stars are plotted to 8th magnitude. Comet Elenin quickly moves up day by day from the eastern horizon, while Comet Honda slowly drops toward the horizon. The time shown is 90 minutes before sunrise. Created with Chris Marriott's SkyMap software.

Both comets are very low in the eastern sky at the start of dawn or about 1 1/2 hours before sunrise for northern latitudes. Elenin starts off tomorrow morning at just 4 degrees high while Comet Honda does better at 11 degrees or about one fist above the eastern horizon. Notice though how quickly Comet Elenin shoots up from the horizon. By the 9th and 10th, it will lie straight across from Regulus and 25 degrees high – perfect conditions for seeking from places where trees block the horizon. The higher up objects are, the less air their light must travel through and therefore the less light absorbed. That means that as the comet vaults higher in the sky, its faint remains will be easier to see. That’s assuming there’s anything left that amateur-sized telescopes can pick up. Comet Elenin was last seen at around 10th magnitude – visible in 6-inch and larger telescopes – but may be much fainter now.

After the 10th, a bright moon (full on the 11th) will make it impossible to see any faint comets in the morning sky for a period of about 10 days. You’ll need to get cracking in the next week if you have a telescope, clear skies and any hope of seeing the comet. I’m one of those guys with a lot of hope when it comes to astronomy, so I’ll be out later this week squinting through the eyepiece and report back on what if anything is out there.

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

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.

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

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

Move over Elenin, Comet Honda’s back in town

A series of images of the UARS satellite made with a 14-inch telescope by French astrophotographer Thierry Legault. The satellite is tumbling possibly from being hit by satellite debris in the past. Credit: Thierry Legault

First, an update on the UARS (YOU-ours). Its orbit now takes it to within 120 miles of the Earth’s surface as the satellite continues to drop hour by hour. For reference, the space station orbits about 225 miles high. NASA still doesn’t know exactly where it land, but the bus-sized bird is predicted to enter the atmosphere sometime on Friday. I’ve seen forecasts by long-time satellite watchers placing UARS’ decay possibly near New Zealand and/or Japan but to be honest, everything’s still up in the air.

Log in to Heavens Above or click HERE and enter your zip code to see if UARS will make any final  appearances over your home before its demise. Observers have reported that it’s now as bright as the brightest stars with occasional flashes as bright as Venus!

While Comet Elenin may have broken up and faded, we still wait with great anticipation to see if its remnants will show in the Solar and Heliospheric Observatory’s C3 coronagraph, a device that blocks the brilliant solar disk so astronomers can see and study the sun’s outer atmosphere. Its field of view is large enough to include background stars, the passing planets and the occasional comet that happens to swing by. Elenin will arrive at the far left edge of the view sometime on Friday and exit to the upper right around September 28-29.

Comet Honda strikes a beautiful form with a bright coma and crisp, westward-pointing tail in this photo taken this morning (Sept. 21) through a 10-inch telescope from Rome, Italy. Credit: Danilo Pivato

While Comet Elenin may be a goner, another comet that’s aroused interest this year has quietly returned to the early dawn sky. 45P/Honda-Mrkos-Pajdusakova, which we’ll abbreviate to Comet Honda, is shining at around 7th magnitude low in the east not far from the bright star Regulus. Moonlight will interfere with the view until this weekend. Find a location with a wide open view of the eastern horizon and start looking about 1 1/2 – 2 hours before sunrise. Your best bet is to locate bright Regulus and “star hop” from it to the comet.

The view facing east 1 1/2 hours before sunrise. Comet Honda will only be about 10 degrees high in a dark sky before dawn's first light. Stars are shown to about mag. 5.5. Brighter ones like Regulus, Omicron and Rho are labeled. Created with Chris Marriott's SkyMap software

Since it’s been cloudy here, I haven’t been out to see Honda yet, but the forecast looks great for the weekend, so I plan to set the alarm clock soon. While it should be visible as a small, fuzzy glow in 50mm and larger binoculars, until the moon has dwindled to a very thin crescent, you may need at least a small telescope to see the comet. Once the moon’s gone, it’ll be fair game for binoculars. The tail stands out boldly in the photo, but will appear much fainter in a telescope. Use the map above to help you locate it.

One last thing. There’s no need to be concerned over Comet Honda. It makes  regular returns to the Earth’s vicinity approximately every five years. On August 15 it passed closest to Earth at a distance of 5.6 million miles. Since then Honda’s been moving away from our planet with a current distance of 61.4 million miles. Astronomers have determined that the comet itself – the solid but friable body inside the bright coma –  measures about 1/2 mile across.

Good luck in your Honda search, and let us know what you see.

Comet Elenin teaches us to sit still and pay attention

Photos taken in an 11-inch telescope by Australian amateur astronomer Michael Mattiazzo clearly show how Comet Elenin has faded. The left image was taken on August 3, when the comet was steadily brightening; the right on September 14 after perihelion.

There’s sure been a lot of excited talk about the disintegration and disappearance of Comet Elenin this week, but we must be careful not to jump to conclusions based on only a small amount of evidence. I don’t think there’s any doubt that the small, several kilometer-wide comet body itself has broken into pieces, which are now vaporizing into a cloud of dust and gas. That began around the 19th of August when Comet Elenin started to fade and its coma became much more diffuse. The breakup was caused by heat and gravitational stresses from the sun in advance of its closest approach to the sun on September 10th. This behavior is not unusual and has been observed in other comets in the past. It demonstrates to us again that comets are not dense, rock-hard bodies like many of the asteroids. Being composed of ices and dust, they’re subject to break up and dissolution from the sun.

As a single, solid body, the comet has not survived, however the fragments have obviously continued to spew dust and gas, enough to still see a what’s left of the comet in the image taken on the 14th, four days past perihelion. Its brightness at that time was about magnitude 10.5.  Mattiazzo also has a photo he took with a telephoto lens on that date which doesn’t show the comet at all. This isn’t surprising since a 300mm telephoto doesn’t have the light gathering power of a telescope.

In this photo taken with a 300mm telephoto lens on Sept. 14, the comet is invisible, because the image doesn't record fuzzy objects like galaxies and comets below magnitude 10.1, the brightness of the galaxy NGC4697. Credit: Michael Mattiazzo

His observing conditions also have to be taken under consideration. In both photos, Comet Elenin was only 7 degrees above the horizon, which is very, very low. At that altitude, light from stars and other celestial objects is absorbed by the thickness of our atmosphere like a sponge soaking up water, making them appear much fainter than when higher up. Since his photo shows a 10.1 magnitude galaxy, all we can say for certain is that the comet is fainter than the galaxy or roughly below about magnitude 10.5.

So is the comet there or gone? I’m sure that the dust cloud is still there but faint and difficult to photograph because of low altitude and evening twilight. A larger telescope and better conditions would undoubtedly show it. Indeed the comet may be 11th magnitude and just below the limit for Mattiazzo’s scope. Because it will get even closer to the sun from our perspective in the coming days, it may well be impossible to photograph again until it swings into the dark morning sky in mid-October.

As I’ve mentioned before, the comet may appear in the Solar and Heliospheric’s LASCO C3 coronagraph photos beginning a week from today on the 23rd, but I doubt it. The remnant dust cloud will likely be too dim and diffuse to show.

I want to make clear that whatever is left of Comet Elenin when it passes nearest the sun on September 26 will have no effects on Earth. This date shouldn’t be confused with perihelion, which is the time of closest solar approach. It will only appear close because Elenin will lie approximately between the Earth and sun. There will be no three days or even three seconds of darkness like some of you have been reading online. Not only will the comet completely miss the sun by 2 full degrees (equal to four full moon diameters), but the dusty cloud is so exceedingly rarefied it will be undetectable even in a telescope. Rest easy.

I’m eager to see what October will bring. It certainly looks like a large telescope and dark skies will be needed to make out what’s left of the comet. Pity. But there’s a lesson here. No matter what machinations and purposes humans may want to attribute to this little comet, it’s a piece of the natural world and will do what it does. If we turn down the noise, we can better see a comet or any celestial object for what it is rather than what we want it to be. Nature is the best teacher, but we need to sit still and pay attention if we’re to fathom her creatures.