Tag Archives: Elenin

Will a comet clobber Mars next year?

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Photo illustration of a comet passing near Mars in 2014. Credit: Comet R1 McNaught by Michael Jaeger; Mars photo by Emil Kraaikamp

On January 3, 2013 comet C/2013 A1 was discovered photographically by Robert McNaught at Siding Spring Observatory in Australia. At the time it was over 7 times farther than Earth from the sun and extremely faint. Though far from Earth’s perspective, this dusty dollop of ice had probably been on its way from the Oort Cloud, a massive and distant comet repository at the fringe of the solar system, for millions of years.

Comet C/2013 A1′s orbit cuts a steep path through the plane of the planets. Right now the comet is well below the plane but is on its way “up”. On October 19, 2014, it will pass extremely close ot Mars. Credit: NASA/JPL

Although not expected to pass particularly close to Earth next year, the comet will have a very close brush with Mars. Leonid Elenin, Russian comet hunter and discoverer of the famed Comet C/2010 X1 Elenin, has examined C/2013 A1′s orbit and found there’s a small chance it could collide with the planet Mars on October 19 next year.

Based on 74 days of observations plus the latest data from Elenin, which admittedly only cover a short piece of the comet’s arc, A1 could zoom as close as 22,990 miles (37,000 km) from the surface of Mars and shine 40 times brighter than Venus at magnitude -8.5 … as seen from Mars that is. Earth observers will see it around 8th magnitude, so you’ll need a pair of binoculars at minimum.

Since a comet’s tenuous outer atmosphere – called a coma -  is typically around 62,000 miles (100,000 km) across, C’/2013 A1 is practically guaranteed to give the planet a gentle powdering.

Diagram showing how the orbit of the comet intersects the orbit of Mars on October 19, 2014. Credit: Leonid Elenin

Given the close brush, there’s even a possibility – for now – that it might crash right into the Red Planet.

This is where things get interesting. Astronomers estimate a comet’s size by measuring how its brightness changes during its approach to the sun. C/2013 A1 turns out to be a potentially BIG comet with a diameter estimated at up to 31 miles (50 km) across.

Its orbit is also tipped over so far (greater than 90 degrees to the plane of the solar system) A1 travels in retrograde motion opposite the direction in which the planets move around the sun. Should it aim for Mars, the two bodies will hit head-on with the comet speeding at 35 miles per second. Dare I say, the energy released from the impact would be prodigious.

Here’s Elenin’s take: “This kind of event can leave a crater 500 km (310 miles) across and 2 km (1.2 miles) deep. Such an event would overshadow even the famous bombardment of Jupiter by the disintegrated comet Shoemaker–Levy 9 in July 1994, which by some estimates was originally15 km (9 miles) in diameter.”

A blast that powerful would easily be visible from Earth as a brilliant flash of light followed by a massive cloud of debris expanding over the Martian landscape and high into the planet’s atmosphere. From Mars, the event could be photographed by one of several Mars-orbiting satellites or even the Curiosity rover. Even if the comet misses the planet, we’d hope NASA or ESA (European Space Agency) could point a camera to take the first-ever photos of a comet from another planet.

The view from mid-northern latitudes facing southwest on October 19, 2014 when the comet and Mars will be extremely close in the evening sky after dusk in Ophiuchus near the “Teapot” of Sagittarius. The path shows the comet’s position every five nights. Created with Chris Marriott’s SkyMap software

Could this all be crazy talk? Maybe. In order to make a firm prediction of exactly what path the comet is on, astronomers will accurately measure its position and refine its orbit in the coming months. Chances are, it won’t hit, but the possibility remains … for the moment.

As for Earth, we’re in the the clear. C/2013 A1 will miss us by 84 million miles even when closest in early September next year. If we assume for a moment that the impact will happen, sky watchers in the eastern hemisphere will have the best seats. I checked the the positions of comet and planet in SkyMap, a highly accurate planetarium program, and determined the time of closest approach to be around 5:30 a.m. Central Time Oct. 19, Mars won’t be up in the sky for the U.S. but will be for much of Russia, China and other eastern hemisphere countries. For observers there, a possible impact would occur during early evening hours on Oct. 20.

Mars will be in the constellation Ophiuchus at that time and low in the southwestern sky at the end of evening twilight. For observers in the U.S., Canada and South America, the planet and comet, should it survive, will be only about half a degree apart at dusk the evening of the 19th. Big blast or not, they’ll certainly make for a memorable sight in a telescope.

Comet Garradd still going strong; Russian Mars probe contacted!

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Comet Garradd on November 19 shows a classic dual tail. The longer, blue streak is the ion tail. The dust tail is shorter and glows pale yellow from reflected sunlight. Credit: Michael Jaeger

Remember Comet Elenin? Hopes were high it would become the best comet of 2011, but instead it dissolved into a cloud of dust. Amateur astronomers are still tracking its fading remnants as the comet passes the Pleiades star cluster in Taurus this week.

Use this finder chart to track down Comet Garradd. It inches slowly northward only a few degrees in the coming month. The map shows Hercules at around 6 p.m. at the end of evening twilight in the western sky. M13 is a bright globular cluster and stars are shown to 7th magnitude. Created with Chris Marriott's SkyMap software.

The brightest comet of the year never received the dire publicity that stuck with Elenin to the end. Comet Garradd was well-placed and easily visible in binoculars this summer as it crossed the Milky Way en route to its current residence in the sprawling constellation Hercules. Underdog Garradd remains a 7th magnitude fuzzball in binoculars this month. I looked it up recently on one of the few clear nights we’ve had in November and was thrilled to see two tails sticking out of the comet’s bright, fuzzy head or coma. Both show wonderfully in Michael Jaeger’s photo and were just as pretty in my 15-inch scope though much more subtle.

Comet Garradd is 195 million miles away or about twice our Earth’s distance from the sun. That gap will close to 118 million miles by early next March, when the comet will brighten by a magnitude, placing it within naked-eye range from the countryside. Take a look now before it drops too low in the western sky and the moon returns. The best viewing time is right at the end of evening twilight as soon as the sky gets dark.

Binoculars still show a soft, puffy glow and perhaps a hint of a tail. A modest-sized telescope will show the dust tail and maybe even a hint of the ion tail. Dust tails are formed of smoke-sized particles of dust embedded in cometary ice. Heat from the sun vaporizes the ice and releases the particles which fall behind the comet in the form of a tail measuring between 600,000 and 6 million miles long. Comet dust reflects light just like good old house dust or cigarette smoke. Ion tails fluoresce blue when ultraviolet light in sunlight breaks down carbon monoxide jetted by the comet and are often much longer – up to 100 million miles.

The European Space Agency's Perth, Australia radio telescope that contacted Russia's Phobos-Grunt craft yesterday. Credit: ESA

Just got the news this morning that contact was re-established with the Phobos-Grunt mission that’s been stuck circling the Earth since its November 8th launch. You might recall the probe’s engines failed to fire and send the ship to Mars. Yesterday at 2:25 p.m. CST, the European Space Agency’s (ESA) tracking station at Perth, Australia, picked up a radio signal from the probe. ESA is now working with engineers in Russia on how best to maintain communications with the spacecraft. Another contact will be attempted tonight.

There’s no information on what might have gone wrong with Phobos-Grunt or how it might be remedied. If engineers can establish a solid communications link with the craft and learn how to correct the engine-firing problem, it might still be sent on its Mars-Phobos mission, but probably not anytime soon. The next launch window opens in 2013. Full story HERE.


A well-narrated and illustrated summary of how we’ll study Gale Crater with the Curiosity Rover.
Meanwhile the Mars Science Lab Mission (Curiosity Rover), which was originally scheduled for a Nov. 25 launch, has been delayed one day to replace a battery on the rocket. Blastoff is scheduled for 9:02 a.m. Central time this Saturday. Click this Mars Exploration Family Portrait by Jason Davis for a really cool graphic showing all missions to Mars to date.

Jupiter Act II, space station flybys and what’s up with Comet Elenin

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The last quarter moon will lie directly between the Seven Sisters star cluster and Jupiter very late tonight and into tomorrow morning. This map shows the sky around midnight. Because the cluster is fainter than the planet, try blocking the moon with your thumb or fist to see it best. Created with Stellarium

Jupiter and the moon sure looked pretty last night. We fought clouds for a while, but it cleared late and the pair was spectacular. Since the moon was still high in the west and near the planet this morning, I wondered whether I might still see Jupiter in my little 8×24 binoculars using the moon as a guide. Hey, no problem! I picked it up at the 7 o’clock position on the opposite side of the field from the moon.  Without a dark sky to make it pop, the planet appeared instead as a pale white disk against the blue sky. I tried to spot it with the naked eye, but no luck.

Although they’ll be farther apart tonight, you have one more opportunity to see Jupiter and moon in the same part of the sky this month. Go out late — around midnight again — and look to the east. The Pleiades or Seven Sisters star cluster joins the mighty duo as well, adding a soft luster to the scene. Once you find the cluster, use binoculars for a really great view of all the stars packed into its tiny dipper shape.

The ISS cuts across the Handle of the Big Dipper this past Thursday night the 18th. The North Star is at upper right. Details: 30mm lens at f/2.8, ISO 400 and 2-minute exposure. Photo: Bob King

Earlier in the evening, the International Space Station (ISS) will make multiple passes across the northern sky tonight and throughout the week. Below you’ll find a listing of times and where to look for the Duluth, Minn. region. For times for your town, go to Spaceweather’s Satellite Flyby site and type in your zip code or log on to Heavens Above. When first seen low in the west, the ISS looks like a bright star, but when higher up it rivals Jupiter in brightness.

* Tonight Aug. 20 starting at 9:18 p.m. and passing through the Big Dipper’s “Pointer Stars” in the northern sky. A second brief pass in the northwestern sky at 10:54 p.m. in the Big Dipper.

* Sunday Aug. 21. Two nice passes in the northern sky, the first at 8:20 p.m. and the second at 9:56 p.m.

* Monday Aug. 22 at 8:58 p.m. followed by a second brief appearance in the northwestern sky in the Big Dipper at 10:34 p.m.

* Tuesday Aug. 23 at 9:36 p.m.

* Wednesday Aug. 24 at 8:38 p.m. and then another shorter pass at 10:14 p.m. The ISS will enter Earth’s shadow and fade from view directly above the North Star around 10:17 p.m.

Two views of Comet Elenin on August 19. At left, Terry Lovejoy captured the comet's bright head and better than 1-degree faint tail through a wide-field 8-inch telescope. At right, Michael Mattiazzo used higher magnification with an 11-inch scope along with a special filter to reveal the comet's tiny bright nucleus inside the coma.

Next, I want to share two excellent, recent photos taken by astrophotographers Michael Mattiazzo and Terry Lovejoy, both expert observers living in Australia, where Comet Elenin is best seen this month. In Lovejoy’s photo, the comet shows a classic comet form with a teardrop-shaped bright head and skinny tail extending away from the coma opposite the sun. Mattiazzo’s more magnified image captures Elenin’s appearance in a telescope with its bright nuclear region buried inside the fuzzy coma or cometary atmosphere.

Comet Elenin is around 8th magnitude and had been brightening steadily over the past few weeks, however Mattiazzo noticed an apparent drop in brightness of about half a magnitude tonight (Aug. 20) Australia time. Other confirming observations will be needed to determine if the comet is indeed fading.

Whether it fades, stalls or becomes brighter than expected, the important thing to remember about comets is that they’re subject to change. We’re talking about small, fragile bodies composed of ices and dust. When near a big, hot object like the sun, solar heat and light make comets come alive with comae and tails. Depending on a comet’s size, distance from sun and Earth and particulars of its ice and dust content, they can appear bright, faint or change without warning. Over the years, I’ve watched many comets follow expectations, but every now and then, one will unexpectedly fade or become brighter than predictions.

The Hubble Space Telescope photographed the breakup of one of Fragment B of Comet Schwassmann-Wachmann 3 in April 2006. Credit: NASA/ESA

Sometimes the comet body itself, the tiny object buried in all the dust and gas, will break into pieces. If those fragments survive (many don’t), each becomes its own mini-comet that follows in the orbit of the parent. Comet 73P/Schwassmann-Wachmann 3 showed multiple “nuclei” in 1995, 2001 and 2006 and was a blast to observe in amateur telescopes.

While Elenin will probably not provide this kind of drama, its evolution as it swings near the sun will certainly keep amateurs busy and hopefully encourage many new to astronomy to look up.

Comet Garradd in 3D, new video of Comet Elenin and a meteor alert

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Two separate photos taken at different times of C/2009 P1 Garradd earlier this month can be "squeezed" into a 3-D picture by crossing your eyes. Credit: Patrick Wiggins NASA/JPL Solar System Ambassador to Utah

Can you cross your eyes? If so, try seeing Comet Garradd, the sky’s currently brightest comet, in 3-D. Sit back about 10 inches to one foot from your monitor, relax and slowly cross your eyes while looking at Patrick Wiggins’s photo above. When the two images blend together correctly, you’ll see the combined stereo view as a “separate” picture floating between the two. Once you get it to work, I think you’ll be delighted with the view. The tail seems to reach into the background of space.

I took at look at Comet Garradd last night in 10 x 40 binoculars and was surprised to see it easily from home even in moonlight. It’s in a great place right now, located just above diminutive Delphinus (del-FINE-us) not far from Altair in the Summer Triangle. Currently shining at about 7.5 magnitude, Garradd looked like a bit of smoke or haze through low power binoculars. In my 10-inch reflecting telescope, I could easily see the comet’s bright head, brilliant nuclear region, which looks like a fuzzy star, and a tail as long as the full moon is wide.

Comet Garradd sails from Delphinus through Sagitta the Arrow above Aquila the Eagle during the next several weeks. The map shows the sky facing south around 10 o'clock. Stars are shown to magnitude 6.5. Created with Chris Marriott's SkyMap software

With the moon going bye-bye into the deep night this week, this is a good time to renew your views of the comet. Use the chart above to get you there. Key in on Altair, the bright star that marks the bottom apex of the Summer Triangle.  One fist held at arm’s length to the upper left of Altair will bring you to the compact constellation of Delphinus the Dolphin. Above and to its right is another small constellation, Sagitta the Arrow. Comet Garradd will look like a small fuzzy spot in typical 10 x 40 or 7-10 x 50 binoculars. Those with telescopes will see a bright head and faint tail pointing south. The comet is 130.5 million miles from the Earth today. Watch for it to slowly brighten through the remainder of summer and fall.

Comet Elenin photographed between Aug. 6 and 12 by NASA's STEREO-B sun-observing probe. Click photo to watch a video of the comet's motion. Credit: NASA

Comet Elenin continues to brighten and now glows at 8th magnitude, bright enough to see in binoculars from a dark sky site in the southern hemisphere. The STEREO-B spacecraft took a series of images of the comet as it passed between it and the sun. The pictures were compiled into the video above which shows the comet’s progress from August 6 through 12. Watch out! It’s a 28MB file and takes a while to load.

Multiple photos of Comet Machholz shot by STEREO-A in 2007 show forward scattering at work as you follow the comet from left to right across the frame. Credit: NASA

You’ll notice as you watch, that the comet brightens somewhat as it travels across the field of view. This additional brightening is caused by ‘forward scattering’ also known more familiarly as backlighting. When a thin cloud of vapor, puff of smoke, or dusty comet tail passes between us and the sun, the small particles scatter the sun’s light with great efficiency and create a temporary brightening. In the sequence of pictures above, taken of Comet Machholz by the STEREO-A craft in 2007, the brightness surge is obvious. Comet Elenin’s is less so, indicating it’s a rather small comet, and that at least for now, is producing more gas than dust.

Speaking of meteor dust, a brilliant fireball was detected by all-sky cameras from the Southern Ontario Meteor Network at 1:22 a.m. Eastern time on Aug. 8 over Lake Erie, according to Bill Cooke, head of NASA’s Meteoroid Environments Office. This was a slow-moving fireball – unrelated to the Perseid meteor shower – that penetrated down to 24 miles altitude before it was lost to radar.

Based on Doppler radar echoes and brightness, the incoming meteor was estimated to weigh about 22 lbs. and may have showered the countryside east of Cleveland with small meteorites. If you live in that part of the country, consider going on a meteorite hunt. Freshly-fallen meteorites are often covered in velvety black fusion crust with pale gray interiors that show brilliant flecks of iron-nickel metal. Click this Google map link via Spaceweather that features push-pins over several possible fall locations.

Comets, meteors and Venus, oh my!

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At least eight Perseids, including a bright fireball, were captured in this compilation of still frames made with a video camera early Friday morning by amateur astronomer John Chumack of Ohio. The moon, seen near bottom, was recorded multiple times as well.

So how did you fare by the Perseid meteor shower? Anyone make a wish upon a star? The sky grew darker and darker with clouds yesterday evening, so much so that I had to use averted vision to finish mowing the lawn. A half-hour later the rain started and didn’t quit. No, there was no joy in Duluthville for the Perseids.

Just as the shower was active before this morning’s maximum, it will still spit meteors earthward for the next several evenings post-maximum, declining to about 10 per hour by the 15th. Since the forecast includes no rain for a change, I’ll poke my head out again for a look-see.

The Draconid meteor shower, which peaks on October 8, is the next shower up at bat. This one is normally a very weak, but because we’re expected to pass through a tendril of thicker dust in the debris stream of the shower’s parent comet, Giacobini-Zinner, much more activity is forecast. I’ve seen rates of up to 750 meteors per hour predicted! Let’s hope it comes to pass.

During the 1946 return, one group of observers in the U.S. counted 3000 meteors per hour at maximum. That year was very favorable as the Earth crossed the comet’s orbit just 15 days after the comet passed through the inner solar system. Lots of freshly-shed dust lit up the sky.

Comet Elenin photographed by NASA's Stereo-B solar observation satellite on August 6. A short tail streams away from the comet's head. Credit: NASA

With a bright moon running amuck, smudgy comets will be faint or impossible to see for the next week or so. As we enter this lull, let’s revisit our two brightest comets. The latest observations of Comet Garradd pegged it at around magnitude 7.5 and easily visible in binoculars from a reasonably dark sky. Comet Elenin continues to brighten. As of August 7, Michael Mattiazzio of Australia observed it at magnitude 9 with a diameter of three arc minutes or 1/10 the size of the full moon. Alexandre Amorim of Brazil posted a similar observation on August 6.

Venus photographed near the sun earlier this morning by the C2 coronagraph on the space-based Solar and Heliospheric Observatory. A metal disk blocks the brilliant sun (white disk) allowing astronomers to see the sun's corona as well as bright planets nearby. Credit: NASA/ESA

Last night I watched a great an episode titled Cold Hands, Warm Heart of the 1960s sci-fi TV show Outer Limits. In it, Star Trek actor William Shatner plays an astronaut who recently returned from a flight to Venus. All seems to be well at first, but something he experienced there soon makes him like VERY hot coffee. You can watch it HERE.

Maybe you’ve been wondering where Venus has disappeared to for the past couple months. The planet has been near the sun for some time and only visible in the daytime sky using a telescope, solar filter and great care in finding.

As Venus revolves around the sun, we see it go through phases like the moon as the Earth-sun-Venus angle changes over time. It's currently at full phase on the opposite side of the sun from Earth. Illustration: Bob King

From our earthly perspective, Venus will be in superior conjunction with the sun this coming Tuesday August 16. That’s when the planet is lined up behind the sun and farthest from Earth. Although the picture above makes Venus look like it’s right next to our star, try to picture it in 3-D with the planet 68 million miles in the background behind the sun. Because it’s so far away, Venus looks like a very tiny ‘full moon’ in a telescope.

After next Tuesday, Venus moves to the left or east of the sun and slowly returns to the evening sky this fall.

Speedy Comet Honda to pass near Earth next week

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Comet Honda-Mrkos-Pajdusakova photographed by Australian amateur astronomer Terry Lovejoy on August 5.

It wasn’t but a week ago I was observing Comet Honda-Mrkos-Pajdusakova, which for simplicity we’ll call Comet Honda-M-P. It was very low in the southern sky in the early morning hours and a tough catch in the constellation Pisces Austrinus the Southern Fish. Using the “lure” of time, I made two observations – one around midnight and the other at 2 a.m. This way I was able to track and positively identify a faint, round hazy glow that slowly inched across the starfield over the span of two hours. Terry’s photo above captures its appearance well.

Sure wasn’t much to look at, but finding an old friend is always a pleasure. I last saw the comet back in 2001 and before that in 1995. Honda-M-P is what astronomers call a returning or periodic comet, similar to Halley’s Comet but with a much smaller orbit and hence a shorter times between returns. It was discovered by Japanese amateur astronomer Minoru Honda in 1948 and seen at nearly the same time by astronomers Antonin Mrkos  and Ludmila Pajdusakova.

Honda belongs to the short-period Jupiter family of comets or those with orbits less than 20 years under the control of the gravitational powerhouse Jupiter.  As it orbits the sun with a period of 5.3 years, it occasionally makes close passes to the planets Venus, Earth and Jupiter. When near Jupiter, the planet’s powerful gravity can alter the comet’s orbit and change its period slightly. This last occurred in 1983 and will again in 2030.

Comet Honda-M-P covers a lot of ground in the next week, plunging through the southern constellations Grus, Tucana, Hydrus and Dorado as seen from Australia. Credit: Chris Marriott's SkyMap

Next Monday August 15, Honda will pass very close to the Earth – relatively speaking – at a distance of just 5.6 million miles. To put this in perspective, that’s 23 times farther than the moon or still a long ways off. I’ve been asked if the comet will affect the Earth in any way, and the answer is ‘no’. Honda is only 0.6 miles across and far too tiny to produce any measurable effects on our much more massive planet. If anything, it’s the other way around. Earth may very slightly alter the comet’s orbit.

When I saw the Comet Honda-M-P, it was very faint in a large amateur telescope (15-inch). Today it’s brighter at magnitude 8.5 with a coma or cometary atmosphere measuring about half the size of the full moon.

If you’re worried that Earth might pass through the coma, don’t be. At Honda’s present distance of 9.3 million miles, the hazy glow around the tiny cometary nucleus is about 43,000 miles across, much too small to reach out and brush our planet. Even if we did pass through a comet’s outer coma, its effects would likely amount to a nice show of meteors at best. Comas are highly rarefied – any ice, dust or small rocks would quickly vaporize on striking the upper atmosphere.

Comet Honda-M-P animation compiled using photos taken on July 21. Click for more comet photos. Credit: Michael Mattiazzo

The closer a celestial object is to Earth, the faster it appears to move across the sky. Because the comet is closing in on minimum distance from Earth, it’s quickly picking up speed, covering more and more ground as we approach the 15th. Tonight for instance, it travels some two degrees or four times the full moon’s diameter in the southern constellation of Grus the Crane. Tomorrow that increases to three degrees, and by the 14-15th, Honda-M-P flys across some 10 degrees of sky- your clenched fist held at arm’s length – in just one night!

The next night or two, the comet will still be visible from the far southern states low in the south around 1 a.m., but by the 14th, only southern hemisphere observers will see it. To spot the comet, you’ll need at least a small telescope, since it’s very diffuse and will get no brighter than 8th magnitude. The moon will also be near or at full phase, lighting up the sky and making it even harder to find.

Two side-by-side binocular comets at dawn in Leo on October 7. Created with Chris Marriott's SkyMap

After closest approach, Honda-M-P swings back north and slowly continues to brighten, reaching 6th magnitude (naked eye limit) in late September, and finally appearing in the morning sky before dawn for northern hemisphere sky watchers in early October. It’s expected to be an easy binocular comet then, shining around 7th magnitude.

On the morning of the Oct. 7, it will be joined by Comet Elenin four degrees (eight full moons) to its north. Although both comets will be at different distances from Earth – 90 million miles for Honda-M-P and 22 million for Elenin -  they’ll lie in approximately the same line of sight. With wide-field binoculars you’ll be able to catch them both in the same field of view. What a wonderful and rare sight this will be!

Speaking of Comet Elenin, southern observers continue to observe and photograph it. It’s now magnitude 9 with a 3-4 arc minute coma and visible in 4-inch and larger telescopes. Click HERE for the latest views of the comet with the STEREO-B (behind) solar telescope.

Got dark skies? See a comet this week!

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The Summer Triangle at nightfall in early August. The triangle is large and covers a sizeable chunk of sky. Created with Stellarium

Summer’s best and brightest nighttime asterism sails high over our heads as August opens. The Summer Triangle and the magnificent stretch of Milky Way it contains command the southeastern sky at nightfall. Altair in the constellation Aquila the Eagle forms the triangle’s bottom apex. For observers at mid-northern latitudes, it’s at eye level as you face to the south-southeast. Three fists held at arm’s length above Altair lies Vega in Lyra the Harp. At 10:30 p.m. local time, this prominent white star is nearly overhead.

Vega is the sky’s 5th brightest star, right behind Arcturus, which flashes like a ruby in the western sky. The eastern apex of the Summer Triangle belongs to Deneb in the constellation Cygnus, also near the top of the sky about two fists across from Vega. Once you’re familiar with these three summer sparklers, you can use them as familiar landmarks to navigate to other stars and constellations.

Italian comet observer Rolando Ligustri made this fine image of C/2009 P1 Garradd (left) as it approached the globular cluster M15 in Pegasus last night July 31. He photographed the comet 'remotely' via computer using a wide-field refracting telescope in New Mexico.

We’ll use the Summer Triangle to help us find Comet Garradd, the brightest comet currently visible in the sky. Don’t fret if you don’t have a telescope. You can already see this fuzzball in 7×50 or 10×50 binoculars if you’re observing from a dark site with minimal light pollution. I saw it two nights ago in my 10x50s just above the star Enif near the Great Square of Pegasus. OK, it was only a blob but it gave me a kick just the same.

But wait, there’s more!

The comet will pass very close to the bright globular cluster M15 Monday and Tuesday nights August 1 and 2. That means you’ll see two side by side blobs. Does life get any better? Telescope users will have the best view when the comet and its fat, short tail make a striking contrast with the rich star cluster. I suspect astrophotographers will burn through more than a few gigs of memory recording the event. Try to catch it this week before a bright moon returns to the evening sky.

Comet Garrad climbs from Pegasus near the star Enif up the Summer Triangle during August. On August 1 and 2, it slides just north of the cluster M15. Enif will guide you to the comet the next few days. It's three 'fists' to the lower left or east of Altair. Created with Chris Marriott's SkyMap software

Comet Garradd is 8th magnitude with a head or coma about 1/4 the size of the full moon (~8 arc minutes). Its tail extends better than half a full-moon-diameter from the head to the south. In a telescope, the bright nuclear or central region looks like a star at low magnification. Binoculars squeeze tail and head together into a small, blurry glow.

The comet keeps getting higher and brighter through the remainder of summer as it slices through the Summer Triangle north of Altair. By September, it will drop lower in the west but remain visible in the evening sky until year’s end for observers at mid-northern latitudes. In early 2012, Garradd moves into the morning sky, brightening all the while. While closest approach to the sun (perihelion) occurs on December 24, closest approach to Earth happens next March 5, when Garradd will be 117.7 million miles away. Then the comet will be ideally positioned in the Little Dipper, shining around 6th magnitude and faintly visible with the naked eye to sky watchers at dark sky sites.

Photo of the coronal hole (top) on July 29 that might cook up auroras tonight. Credit: NASA

As long as we’re on comets, the most recent observations of Comet Elenin from July 30 put it at magnitude 9.5 – 10. Nice to see it’s still climbing in brightness. If you’re out looking for Comet Garradd, keep an eye on the northern sky tonight and tomorrow night. That’s when space weather forecasters are predicting a stream of particles from a large gash in the sun’s atmosphere called a coronal hole to strike Earth’s protective magnetic bubble.  Possible modest auroras might be visible at higher latitudes. Look for a greenish glow or spear-like rays just above the northern horizon. Generally, the closer to midnight – 1 a.m. you’re out, the better chance of seeing northern lights.

The three big naked eye sunspot groups are an amazing sight in this photo taken around 10 a.m. today. Credit: NASA

Those big sunspot groups are still busy and very obvious. I saw all three with the naked eye using a safe solar filter earlier this morning. Group 1263, which has the largest spots, was the easiest to see. Compare this photo to their appearances just two days ago.

Vesta – a most satisfying view! Elenin discovers new comet

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This is the first image obtained by NASA's Dawn spacecraft after successfully entering orbit around Vesta. It was taken from a distance of about 9,500 miles. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

If you haven’t already seen them, here are the latest closeup photos of the asteroid Vesta taken by Dawn. Although the spacecraft has been captured by Vesta’s gravity, mission controllers will work for the next several weeks to tweak the orbit, so the craft is in the best position for studying and photographing the asteroid’s surface. During this time, Dawn will also search for possible moons and take additional pictures of Vesta for navigation purposes. The real science begins next month.

In this side view of Vesta, taken by the Hubble Space Telescope, you can see the central peak protruding from the polar region. Credit: NASA/ESA

In the photo above, we squarely face the huge 285-mile wide impact basin in Vesta’s south polar region. The large mountain at center is the impact hole’s central peak. You can see the rim of the basin best at upper right between the 1 and 3 o’clock positions. For reference, here’s an image taken by the Hubble Space Telescope that shows the peak viewed from the side. The ‘missing’ material that would otherwise round out the bottom of Vesta was excavated by an enormous impact. Judging by the many craters in the area, it must have happened long ago. As for the worm-like grooves, they may be connected to the impact. The difference in detail between the two photos is amazing!

Here are a couple more. Click on the Dawn photos to see mouth-watering full-size versions:

Vesta, at 330 miles across, is the largest of the 8 asteroids we've seen up close with spacecraft to date. Here they're shown with correct relative sizes. Credit: NASA/JPL-Caltech/JAXA/ESA

This 3-D image of the south polar region of the asteroid Vesta was put together from two images taken on July 9. The image shows the rough topography in the south polar area, the large mountain, impact craters, grooves, and steep scarps in three dimensions. Use red-blue glasses to view in 3-D. Credit: NASA

P/2011 NO1 is a tiny spot in this photo taken on July 12 through a 79-inch (very large!) telescope. Credit: N. Howes, G. Sostero, E. Guido

Congratulations go out again to Leonid Elenin! He and I. Molotov discovered new comet P/2011 NO1 ‘remotely’ on photos taken using a computer-controlled telescope at the ISON-NM Observatory near Mayhill, New Mexico. The comet was discovered on July 7 and the news just announced today. Before you get too excited, P/2011 NO1 is incredibly faint (magnitude 19) and becoming fainter as it recedes from both Earth and sun in the coming months. I doubt anyone’s going to see this visually through a telescope.

This second Elenin comet passed nearest the sun on January 22 this year at a distance of 115 million miles. It’s currently 140 million miles from Earth. The letter ‘P’ in its name indicates this is a periodic or returning comet. With a period of 13 years, perhaps we’ll see it sometime in the future when more favorable orbital circumstances bring it closer to Earth. A look ahead shows that on its next round in 2024, it will pass 54 million miles from us. For more on the new visitor, check out the Remanzacco Observatory blog or Elenin’s own website.

What’s new with Comet Elenin

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Smog and fog helped to filter the sun's light and make yesterday's eclipse a spectacular sight over the city of Bratsk, Russia. Credit: Svetlana Kulkova

I hope some of you saw part of yesterday’s partial solar eclipse via webcam and maybe a few of you even saw it for real. In addition to the photo above, check out these pictures taken by B. Art Braafhart from Sallatunturi, Finnish Lapland and Johan Kero of Kiruna, Sweden. Braafhart’s image of the crescent sun at sunset puts a whole new spin on how spectacular a partial eclipse can be!

Comet Elenin photographed with a 16" telescope on May 30, 2011. Notice the small, bright coma and short tail to the southeast. Credit: Erik Bryssinck

I was out last night for another look at Comet Elenin, which may become bright enough this fall to be visible in binoculars and possibly the naked eye. It’s anything but at the moment.

Despite its decreasing distance from the sun, Elenin remains fainter than its predicted brightness at this time, hovering around 13th magnitude – dim! I can speak for how faint and difficult it is to see visually.

Comet Elenin through a 15" telescope with a magnification of 142x last night at 11 p.m. Not much to see ... yet! Illustration: Bob King

I first saw the comet back in April through a 15″ reflecting telescope, and it took more than a half hour to confirm it was really there and not my imagination. My most recent look was last night through the same scope and its appearance was little changed. Elenin had brightened up a bit and moved along its course, but it remains challenging to see, being little more than small smudge with a slightly brighter core. Usually a comet brightens as it distance from the sun decreases, but comet astrophotographers have noticed a small decline in Elenin’s brightness since April. Certainly its rate of brightening has slowed during May.

While it’s not unusual for a fresh comet from the outer solar system like Elenin to brighten early on and then stall or not live up to expectations – think of Comet Kohoutek – let’s hope the comet still has some fresh ice and dust left for a good show.

This photo of Comet Kohoutek was taken on January 11, 1974. Although the comet did become visible with the naked eye, it never reached brightness predictions, disappointing an expectant public. Credit: NASA

In the case of Kohoutek, which graced our skies in late 1973, astronomers believed it was making its first trip to the inner solar system and carried a full complement of highly volatile ices. When exposed to the sun after so many thousands of years in the deep chill of deep space, its ices were expected to vaporize like crazy and loft lots of dust from Kohoutek’s interior into space to create a spectacular tail and brilliant coma. Such rosy predictions never came to pass. When Kohoutek failed to fill the bill, its name quickly became a worldwide joke. Even today, I still hear the occasional “sounds like another Kohoutek” when someone refers to an astronomical event that didn’t live up to expectations.

Comet Elenin recently resumed its normal eastward motion against the stars as it moves through the constellation Leo in the coming month. The tick marks show the comet's position every five days. Credit: Created with Chris Marriott's SkyMap software

We won’t pass judgement so swiftly on Elenin. Comets are sometimes unpredictable. That’s what gives them their charm, and the reason I’ve tracked so many of them at every hour of the night over the years. I like surprises.

Currently Comet Elenin is moving eastward in the constellation Leo the Lion not far from its brightest star Regulus. It coma or cocoon of dust and gas that shrouds the nucleus measured some 62,000 miles across in late May. That sounds huge, but we’re talking the envelope around the actual comet, which is little more than a tiny spark of light buried deeply in the coma’s center. Scientists estimate the comet nucleus itself – what makes the coma -  is a few miles in diameter.

Because of all the dusty mess, it’s very difficult to get a good idea of a comet’s actual size unless you can pull up alongside it with a spacecraft. Here are a few known diameters of comets all determined by on-site measurements by space probes:

1P/Halley = 10 x5 x 4.3 miles
81P/Wild 2 = 3.1 miles
103P/Hartley 2 = 1 mile
9P/Tempel 1 = 3.7 miles
10P/Borrelly = 5 x 2.5 x 2.5 miles

In addition there are good estimates of at least two others, 26P/Grigg-Skjellerup (1.6 miles) and 21P/Giacobini-Zinner (1.2 miles). Other comet nuclei estimates can be found in this detailed scientific paper. As you can see, comets are on the small side just like the majority of those other small solar system bodies, the asteroids. Even Comet Hale-Bopp, which was a spectacular sight in the spring of 1997, has a estimated diameter of 30 miles. Small potatoes, but comets can sometimes put on great shows when they’re actively vaporizing ice at the same time they pass near the Earth.

More about comets and Comet Elenin

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Comet McNaught photographed this morning from Austria. The comet shows a blue-green, gaseous coma and a short tail to the west. Credit: Michael Jaeger

Comets have been in the news a great deal this year. Currently only one is bright enough to see in 6-inch and larger scopes – Comet C/2010 C1 McNaught. It’s sailing eastward through Pegasus the Winged Horse low in the eastern sky just before the start of dawn, and shines weakly at around magnitude 9.5.

This map shows Comet McNaught during its travels through Pegasus this month. It's a fuzzy 9th magnitude object. Created with Chris Marriott's SkyMap software

Interested amateur astronomers can get an idea of where to look using the map at right. For a more detailed map, go to the IAU Minor Planet Center’s Orbital Elements for Software Packages page. There you can download the latest positional information for your particular sky program and create your own locator maps.

Comet Elenin on April 2, 2011 is just a small, fuzzy object in this time exposure photo made through a 12-inch telescope. The stars are trailed because the photographer kept the scope centered on the moving comet. Credit: Bernhard Haeusler

Then there’s much-talked-about C/2010 X1 Elenin. Although there are many photos of it, only two people I know of have seen Elenin visually through a telescope, because it’s still extremely faint.

On the one hand, I’m delighted there’s so much interest in the comet, which may become bright enough to see with the naked eye this October. On the other, I’m amazed that some people suspect there’s some kind of cover-up about the comet’s identity or that its passage through the inner solar system could cause earthquakes and a shift in Earth’s poles.

We’re a superstitious people at heart. The ancient Romans would gladly have loaned an ear to our cometary fears. They shared the same feelings some 21st century humans  still have about these unexpected visitors from the distant realms of the solar system. People of long ago took comets as omens of change, mostly for the worse, because they came unexpectedly and no one really knew what they were. Thanks to hundreds of years of telescopic observation, orbital calculations and a handful spacecraft flybys, including the Stardust sample return mission, we have a darn good idea in 2011 of what comets are.

The orbit of a typical comet. Unlike planets, comet orbits are often very elongated or cigar-shaped. Many arrive from a great distance, swing around the sun and then return to the outer solar system. Credit: NASA

While future studies will undoubtedly teach us more, this we know. Comets are small, friable bodies ranging in size from about 1/4 mile to several tens of miles in diameter and composed of a mixture of ice,  dust and small bits of rock. When one travels through the inner solar system, the sun heats the comet, causing ice to vaporize and form a fuzzy envelope of gas and dust around it called a coma. The pressure of sunlight pushes some of the dust away from the coma to form a tail. Solar ultraviolet light excites some of the other gases to glow in the form of a second ‘ion’ tail.

Most meteor showers occur when the Earth’s orbit crosses that of a comet. Then we encounter the dusty debris left behind, particles of which burn up as flashes of light in our upper atmosphere. That’s a ton more information than was available to our ancestors.

Once a new comet is spotted, by professional sky surveys using automated telescopes, spacecraft or amateur comet hunters (yes, even amateurs still occasionally nab one before the professionals!), its orbit is determined through careful observation of its nightly track across the sky. Once we know a comet’s orbit, astronomers can then predict where the comet will be in the days, months and even years ahead. Orbits tell us things like how close a comet will get to the sun and Earth and how long before it returns for another visit. To date, over 4000 comets have been discovered.

Outline of the 110-mile diameter buried impact crater in the Yucatan Peninsula. Credit: NASA

No comet has been positively confirmed to have hit the Earth. Meteorites from asteroids have, and there’s no doubt that sometime in the past, comets have done the same, but it’s never been recorded in history. The Chicxulub crater in the Yucutan, widely believed to have led to or accelerated the extinction of the dinosaurs 65 million years ago, was created by a six-mile-diameter impactor. The jury’s still out on whether comet or asteroid. By the way, there’s nothing to prevent this from happening again sometime in the future. Earth doesn’t carry pack a magic, impact-deflecting umbrella.

Comet Biela and its breakaway companion comet in February 1846. Credit: E. Weiss from Bilderatlas der Sternenwelt

Being crumbly, comets sometimes break into two or more pieces when heated and gravitationally strained by the sun or large planets like Jupiter. Breakups can release lots of extra dust and gravel bits into the comet’s orbital path. If at some point, Earth intersects a shattered comet’s orbit, we experience a meteor shower.

Biela’s Comet, first spotted in 1772 and recognized as a periodic or returning comet by Wilhelm von Biela in 1826, gave 19th century observers a little surprise. It was seen again in 1832, but when it returned in 1845, Biela had split into two separate comets traveling side by side. Neither was seen during the 1859, 1865 and 1872 returns, however a spectacular meteor shower appeared in November 1872 from the area of the sky where the comet had been predicted to cross in September that year. Because it was known that Comet Biela’s orbit intersected Earth’s, it appears that the breakup of the comet led to the shower.

During the 1832 pass and later predicted returns, there were concerns Biela’s Comet or its coma would impact the Earth.  The only ‘terrible’ thing that happened was a nice series of meteor showers during the remainder of the 19th century.

An illustration from a Chilean newspaper playing upon fears of a collision between Biela's Comet and Earth in 1877. The words say "end of the world".

Depending upon where the Earth happens to be in its orbit when a comet drops by, our distance from it can vary from one return to the next. Only 3.2 million miles separated Earth from Biela in 1805. The closest- ever recorded approach of a comet was Lexell’s Comet in July 1770, when it zipped by Earth at a distance of only 1.37 million miles. No meteors were seen and no cometary tragedies were noted. More recently, Comet IRAS-Aracki-Alcock passed some 3 million miles from us in the spring of 1983. I was around for that one. Its nearness meant the fuzzy visitor moved through the sky with great speed. I watched it travel from one end of the heavens to the other in just three days. Telescopic views were incredible, with a bright central nucleus surrounded by a gigantic coma.

Let’s return again to Comet Elenin. At closest approach on October 17, the comet will be 21 million miles from our planet and 2.4 million miles above our orbit. As comets go, that’s sort of close but not unusual or exceptional. I only hope the Elenin will brighten up as hoped, so we can get a nice view in binoculars.

Sure, anything can happen, but the more fantastic the scenario, the less probable its likelihood. Elenin might split into two or three comets or see its orbit altered slightly due to outgassing of material – even that wouldn’t be unusual. In the meantime, I’ll put my money on orbital mechanics and past experience as guides for predicting its likely future behavior over some of the pseudo-scientific and patently untrue forecasts posted online in recent weeks.