Tag Archives: ISON

Comet Lemmon’s back plus Earth may get peppered with Comet ISON dust

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Comet PANSTARRS glides through the W of Cassiopeia at nightfall in late April. Look low in the northwestern sky about 1 1/2-2 hours after sunset to find it. Moonlight might render the comet invisible in binoculars, but a small telescope will still show it. This map shows the sky facing northwest around 9:30 p.m. local time. Created with Stellarium

As Comet PANSTARRS gallops off into the sunset of deep space, we anticipate the arrival of another fine binocular comet – C/2012 F6 Lemmon. Some of you might recall this comet from earlier in the year, when it reached naked eye brightness for sky watchers in the southern hemisphere and grew a long, ribbon-like tail.

After months of having it as their own, Lemmon will soon appear in the dawn sky near the Great Square of Pegasus at the end of this month in the northern hemisphere. Predictions indicate it might be visible with the naked eye from a dark, rural locale, but there’s no question we’ll see it in binoculars and small telescopes.

Comet C/2012 F6 Lemmon photographed through a 12-inch telescope from Namibia on April 21. Exposure time was 3 minutes. Notice the short dust tail and long, blue electrically-charged ion tail. Click to see more of Rhemann’s comet photos. Credit: Gerald Rhemann

Next week I’ll post a map and directions on how to find it. On May 6, a thin crescent moon will pass a short distance south of Lemmon, providing a helping hand. Comet PANSTARRS will still be out in May and though very faint in binoculars, a small telescope will show it.

I hate to go cometless for very long, so Lemmon’s arrival is welcome. Of course Comet ISON is the year’s BIGGEST celebrity. Circumstances are much better for it than PANSTARRS. ISON will pass very close to the sun in late November, be cooked into a brilliant object and develop a long tail.

Comet ISON is “rounding the corner” in Gemini the Twins this month and still very faint. It’s currently lies beyond the outer edge of the asteroid belt some 400 million miles from Earth. The Swift observation is described below. Credit: NASA

An ideal comet encounter is one where the object first passes very close to the sun then zooms by Earth soon after. This two-birds-with-one-stone trajectory allows us to see the comet near peak brightness and in its full finery. That’s exactly what will happen with ISON.

Views of Comet PANSTARRS were somewhat compromised because it receded from Earth after closest approach to the sun. It also didn’t help that the comet was more than twice as far away (101 million miles / 163 million km) when nearest Earth compared to ISON’s 40 million miles (64 million km) on Dec. 26.

On Nov. 28 Comet ISON will pass only 680,000 above the sun’s surface. Less than month later, it flys by Earth at a distance of 40 million miles. Credit: NASA

All this assumes that ISON won’t bust to bits in the intense heat it will experience during its face-to-face with the sun on Nov. 28. Back on Jan. 30, NASA’s Swift spacecraft aimed its powerful, multi-wavelength eyes at the comet when it was still near Jupiter. Even at that distance, solar heating vaporized enough ice for ISON to spew out 112,000 lbs. (51 kg) of dust a minute.

This is a tiny bit of comet dust captured by a high-flying airplane mission. The particles from ISON are similar in size – about 1/8000 of a inch across. Credit: NASA

Meteor researcher Paul Wiegert of the University of Western Ontario, who’s been using a computer to model the trajectory of dust ejected by Comet ISON, predicts that some of that dust could end up on Earth.

Less than three weeks after closest approach to our planet, Earth will pass through a flurry of the powdery stuff lofted our way by the gentle pressure of sunlight. At the same time, we’ll encounter the dust stream trailing behind ISON and headed toward the sun. Wiegert calls the double-whammy “unprecedented”.

If his forecast is correct, the dust, traveling at 125,000 mph (201,000 km/hr), will pepper Earth’s atmosphere for several days around Jan. 12, 2014. While you might expect to see a meteor shower, chances are slim; the particles are so small, they’ll slow to stop instead of getting fried as meteors by air friction. Still, you never know – maybe a few of the bigger ones will show as meteors.

Noctilucent clouds photographed from the International Space Station. Credit: NASA

As the grit drifts gently down over the months and years, it’s possible it may serve as seeds or “nuclei” for the formation of noctilucent clouds, those eerie, skeletal blue clouds visible from northern locations during the summer months. For clouds to form, water vapor needs some form of dust or grit to latch onto and grow into crystals and droplets.


For a nice visual summary of the Comet ISON dust prediction, check out this video.

Noctilucent clouds, shining in late twilight when all other clouds have gone dark, are nearly as high as the lower limit of the aurora borealis (60 miles / 96 km). While it’s only speculative, it’s possible that bits of Comet ISON may someday contribute to their formation. Wouldn’t that be just too cool?

Comets Panstarrs and Lemmon share a Kodak moment

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Two for the price of one! Comet L4 PANSTARRS is bright dot lower left with a short tail; Comet F6 Lemmon and its skinny tail are visible at right next to the Small Magellanic Cloud, a satellite galaxy of the Milky Way. Click to enlarge. Photo taken on Feb. 17, 2013 from Australia. Credit: Justin Tilbrook

Justin Tilbrook of Australia took a marvelous image earlier this week showing our two current comet celebs F6 Lemmon and L4 PANSTARRS together in the same picture.It’s not often you’ll see two tail-toting comets captured with a wide-angle lens at the same time.

To bring you up to date, Panstarrs is still visible very low above the horizon in morning twilight from far southern latitudes. This week it’s brightened to 4th magnitude and appears like a fuzzy pearl with a short tail. One observer noted a yellow color to the comet’s head caused by dust reflecting the ever-intensifying sunlight as PANSTARRS barrels sunward toward its March 10 perihelion.

Comet Lemmon photographed on Feb. 20, 2013 through a 19.6 inch telescope. Click to enlarge Credit: Martin Mobberley

Lemmon is higher up in the sky but fainter at magnitude 5.5. Right now it might be difficult to see with the naked eye because of moonlight. Binoculars show a bright head and a  1/2-degree-long tail.

You might be interested in a recent study on brightness predictions for comets L4 PANSTARRS and ISON by Ignacio Ferrin of the University of Antioquia in Medellin, Colombia. Here are the main points:

* C/2011 L4 Panstarrs will be less bright than Halley’s Comet was in 1986. It will show
a tail easily detectable with the naked eye.

* There’s a 75% chance that  C/2012 S1 ISON will continue to brighten and put on a great show late this fall. Ferrin predicts it could become as bright as the full moon (magnitude -12.6) when nearest the sun. But his prediction comes with a caution: ISON will pass within the Roche Limit when it swings around the sun in late November. This is the minimum distance a smaller body can hold together in one piece while orbiting a larger body without being torn to bits by the larger body’s overwhelming gravity.

At top, an object like a comet has crossed the Roche Limit and starts to disintegrate into pieces. Below, the individual pieces spread out according to distance. Particles closer to the sun (left) move more quickly (red arrows) than those farther away. Credit: Wikipedia

Ferrin writes: “Any object within this limit  has a large probability of disintegrating due to differential gravitational forces from the Sun. The combinations of Roche’s Limit, plus solar radiation plus very high temperature, suggest that the comet may not survive its encounter with the Sun, disintegrating into several pieces. Or it may survive, if its internal cohesion is
sufficient to endure those conditions.”

If you’d like to learn more, please check out the complete study.

Mid-February bright comet update: Panstarrs, Lemmon, Bressi, Ison

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Comet Panstarrs on Feb. 8, 2013 photographed with a 300mm telephoto lens from Castlemaine, Victoria, Australia. Observers describe very bright head and broad tail. Click to see more comet photos. Credit: Michael Mattiazzo.

There are a lot of icy mudballs , ie. comets, flying around up there at the moment, so let’s take a look at what’s happening. We’ll start with C/2011 L4 PANSTARRS, better known as Comet Panstarrs. It’s been slowly brightening to within naked eye range, hovering now right on the edge of visibility under dark skies. Recent observations by amateur comet observers put the comet a smidge above the naked eye limit at magnitude 5.5-5.7. It’s a snap to see in binoculars in morning twilight in the southern hemisphere. As you can tell from the photo, it has an intensely bright, almost star-like head and wide, dusty tail that’s about 1/2 degree long. It should be a most excellent sight in binoculars for both northern and southern hemisphere sky watchers when it emerges at dusk in the western sky next month. We’re only four weeks away!

What a comet! This is Comet Lemmon shot through a 5-inch widefield telescope on Feb. 8, 2013 from Possum Observatory Complex in Gisborne, New Zealand. Click for large version. Credit: John Drummond

Meanwhile, another comet has temporarily stolen the show. C/2012 F6 Lemmon has swelled into a huge, green leek of a thing, Like Panstarrs, it too is faintly visible with the naked eye (mag. 5.8) under dark skies for southern hemisphere skywatchers. How come they get all the fun?

A long, thin exclamation point of a tail shoots from Lemmon’s giant, whipped-up coma or cometary atmosphere. Good news is, the comet is still brightening and may reach 3rd magnitude, making it an easy sight even from the suburbs.

We northerners will have to be patient if we want a glimpse of this comet. Not until early May, when it swings around the sun and enters the morning sky at about magnitude 5, will we get our chance.

You can see the fading of Comet Bressi in this sequence of photos made by Rob Kaufman of Bright, Victoria, Australia.

Then there’s C/2012 T5 Bressi, a modest, unassuming comet that experienced a bright outburst in late January. In a matter of days it became 10 times brighter than expected. On Feb. 4, Bressi glowed at 9.2 magnitude and then slid to 10.5 the very next day.

Sad to say, this is a bad omen for a comet and usually means the beginning of the end. They are crumbly things after all and subject to breakup as their ices volatilize under the relentless sun. Unfortunately, the nail might get hammered into Bressi’s coffin on Feb. 24, when it reaches perihelion or closest distance from the sun (28 million miles). Some comet observers predict it will disintegrate around that time.

Reversed (negaitve) image of Comet ISON on Feb. 3. At the time, the comet was 4 times Earth’s distance from the sun. Credit: Rolando Ligustri / CARA Project

Finally we come to this year’s best hope for a brilliant comet – C/2012 S1 ISON. It’s still slowly cruising through northern Gemini and beautifully placed for telescopic observation every clear night for observers in the northern hemisphere. Would that it were a tad brighter. You still need a 12-inch or larger telescope to see this 15th magnitude fuzzy blotch. I shouldn’t be so offhanded. Ison has developed a short tail of late, lending it enough character to whet our appetite for things to come.

By late fall, ISON should be an easy binocular object in the morning sky. Come Christmas it’s likely to be a glorious sight at dusk. Tag along with me and I’ll let you know how it goes as the clocks ticks cometward.

Best astronomy events of 2013 – a look into the crystal ball

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What’s in the stars for 2013? Check out the list below. This picture is of the star-forming region NGC 3603 photographed with the Hubble Space Telescope. Credit: NASA/ESA

With 2012 under our belt, we look forward to what the new year will bring. It’s a big, wild sky up there. Below you’ll find a month-by-month listing of some of the highlights. 2013 could go down in history as the year of spectacular comets. Both C/2011 L4 PANSTARRS and C/2012 ISON are expected to become at least as bright as the brightest stars. Comets are unpredictable however, so we’ll have to wait and see. No problem. That’s what we lovers of the sky do best.

JANUARY

* Jan. 3 – Peak of the annual Quadrantid meteor shower during the early morning hours when up to 80 meteors per hour could be seen. A waning gibbous moon will compromise the view and the peak is a very short sliver of time. Observers in Asia are favored.

* Jan. 21 – The waxing gibbous moon has a very close conjunction with the planet Jupiter in the evening sky. They’ll be about one moon diameter apart.

FEBRUARY

Path of asteroid 2012 DA14 during its February flyby. The green circle is the ring of geosynchronous satellites in orbit around Earth. Credit: NASA/JPL

* Feb. 7 and 8 – Mercury passes very close to Mars (0.3 degrees) low in the western sky at dusk

* Feb. 15 - Asteroid 2012 DA14 zooms just 21,000 miles from Earth around 2 p.m. (CST) this afternoon. The 147-foot long boulder will not impact the planet and the chances of it striking a satellite in the geosynchronous belt is near zero. At brightest it will shine at magnitude 7.7.

* Feb. 16 – Mercury at greatest elongation east of the sun and easy to find during evening twilight.

* Feb. 28 – Late tonight the moon will pass just 1/10 of one degree south of Virgo’s brightest star Spica – that’s close!

MARCH

A modest comet on September 9, 2012, C/2011 L4 PANSTARRS is expected to become a fine naked-eye sight in March. Credit: Michael Mattiazzo

* March 8-20 – Comet C/2011 L4 PANSTARRS emerges in the western sky after sunset with a brilliant head and ever-lengthening tail. Its height increases night by night as the comet fades. Expected magnitude of around 0 or about as bright as the star Vega. A much anticipated event! The thin lunar crescent passes close to the comet on the 12th.

* March 20 – First day of spring for the northern hemisphere begins at 6:02 a.m.

APRIL

* April 24 – Another extremely close approach of the waxing gibbous moon and star Spica

* April 25 – Partial eclipse of the moon. Visible from Australia, Asia, Europe and Africa but not from North or South America.

April and May are the best times to view Saturn and its beautiful rings through a telescope. Credit: Damian Peach

* April 28 – Opposition of Saturn when it’s closest and brightest for the year. The planet shines at 0.1 magnitude in Libra and rises at sunset. The rings are nicely open to view and can be seen in any telescope magnifying at least 30x.

MAY

* May 5-6 – Peak of the Eta Aquarid meteor shower. This is modest shower with a rate of about 10-15 per hour radiating from the constellation Aquarius. Best viewed in the early morning hours. Moonlight from the setting waxing gibbous moon will comprise the shower somewhat.

* May 9 – Annular eclipse of the sun. Not visible from North America but will be partial in Hawaii. Path of annularity passes through northern Australia and the tip of New Guinea.

Attractive planet grouping low in the northwestern sky during early twilight on May 26, 2013. Created with Stellarium

* May 22-30 - Venus, Mercury and Jupiter cluster together low in the western sky after sunset. Close conjunctions of Venus and Mercury (24th), Mercury and Jupiter (26th) and Venus and Jupiter (27th-28th). Low but a potentially great show. The southern states will have the better views.

* May 24-25 – Penumbral lunar eclipse visible across North America except Alaska. Keen-eyed observers might notice some shading along one side of the moon as it dips into Earth’s outer shadow called the penumbra. Eclipse starts at 10:43 p.m. CDT and ends at 11:37 p.m. May 24.

JUNE

* June 1 – Striking lineup of Jupiter, Venus and Mercury low in the western sky after sunset. Find an unobstructed horizon to see best.

* First week of June – Mercury well-placed for viewing low in the western evening sky.

* June 21 – First day of summer in the northern hemisphere begins at 12:04 a.m. CST.

JULY

* July 3-4 – Venus returns to the evening sky visible low in the west during twilight. On these dates, binocular users will see the planet pass in front of the Beehive star cluster in Cancer.

* July 21-23 – Conjunction of Mars and Jupiter. Both planets now return to the morning sky and pair up within one degree of each other on these dates. They’re visible in Gemini low in the eastern sky before sunrise.

* July 28-29 – Peak of the Southern Delta Aquarid meteor shower. Up to 20 meteors per hour before dawn radiate from the constellation Aquarius. Compromised this year by the waning gibbous moon.

AUGUST

Perseid meteor. Credit: Kohle Kredner

* August 3-5 – Very nice lineup of Mercury, Mars and Jupiter joined by the thin crescent moon these mornings. Look to the east about an hour before sunrise.

* Aug. 12-13 – Peak of the great Perseid meteor shower. Up to 80-100 meteors per hour are visible especially after midnight. This year the moon is a thick crescent that sets before 11 p.m. and won’t compromise the shower.

* Mid-August – Comet ISON emerges into the dawn sky in the constellation Cancer shining around 11th magnitude, bright enough to spot in amateur telescopes.

SEPTEMBER

* September 5-6 – Venus near Spica low in the southwestern sky at dusk

* September 8 – Fine conjunction of the crescent moon and Venus this evening

* September 19 – Full Harvest Moon

* September 22 – Fall starts with the autumnal equinox at 3:44 p.m. CDT.

OCTOBER

* Maximum of Sunspot Cycle 24 predicted to happen this fall. It appears this will be the smallest cycle since Feb. 1906.

During a penumbral lunar eclipse, like this one in 1999, one edge of the moon is slightly shaded. To the eye, it appears blunted.

* October 18 – Penumbral eclipse of the moon partially visible from North America. The moon enters Earth’s outer shadow (penumbra) at 4:48 p.m. CDT and exits at 8:52 p.m. The shading should be more noticeable than during May’s penumbral eclipse.

* October 21 – Peak of the Orionid meteor shower which originates from dust trailing Halley’s Comet. About 20 meteors per hour radiate from the constellation Orion after midnight. Meteor counts will be reduced due to light from the waning gibbous moon.

* Late October – Comet ISON brightens to magnitude 7 and becomes visible in binoculars

NOVEMBER

* November 1 – Venus at greatest elongation east of the sun. It finally gains some altitude and becomes much easier to see this month during evening twilight.

* November 3 – The only total solar eclipse this year. Visible across the equatorial Atlantic Ocean and West Africa. Not visible in North America.

* Early November – Comet ISON should be visible with the naked eye at 2nd magnitude (as bright as the Big Dipper stars) in the morning sky.

* November 17-18 – Peak of the annual Leonid meteor shower. 10-15 meteors per hour are expected but the full moon will make a big dent in meteor counts.

* November 25-26 – Mercury and returning Saturn meet up together for a close conjunction. The two will be just one degree apart on these dates.

* November 28 – Perihelion of Comet ISON. This is when the comet will be closest to the sun. It’s expected to shine brighter than Venus and visible near the sun in the daytime sky with proper viewing precautions. The comet will look like a star with a short tail.

DECEMBER

It doesn’t look like much in this photo taken on Dec. 9, 2012, but astronomers predict that Comet ISON could become a bright naked eye comet this month. Credit: Rolando Ligustri

* Early thru mid-December – Comet ISON at its best. Visible in both the early morning and evening skies, ISON hurries northward away from the sun’s glow. It’s expected to be nearly as bright as Jupiter with a long tail.

* December 6 – Venus dazzles as it climbs higher and reaches greatest brilliancy for the year.

* December 13 – Peak of the great Geminid meteor shower. About 100 meteors per hour are visible from a dark sky, but this year the waxing gibbous moon will compromise the view until after moonset around 4 a.m.

* December 21 – Winter begins with the solstice at 11:11 p.m.

Hergenrother: Mouthful of a comet worth the bother

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168P/Hergenrother displays a bright nucleus (center of the comet’s activity), a blue, elongated coma (its atmosphere) and short tail on Oct. 3, 2012. Credit: Michael Jaeger

The title is my desperate attempt to find a rhyme for this comet’s wonderful name. While I may not have succeeded, that doesn’t change Hergenrother’s status as the coolest comet in amateur telescopes right now.

With the moon out of the sky, the next few weeks are ideal for those with 6-inch and larger scopes to pursue 168P/Hergenrother, currently the brightest comet visible at mid-northern latitudes.

Thanks to a recent outburst of activity, this fuzzy interloper shines around magnitude 9.5. It’s in a very handy spot, too, located not far from the upper left star in the familiar Great Square of Pegasus. The Square is well up in the southeastern sky by 9 o’clock local time.

Finder chart showing the comet’s nightly position starting Oct. 5 at 9 p.m. (CDT). Hergenrother moves across the northeastern half of the Great Square. The star marked Alpha is Alpha Andromedae, which is shared by the Square. Stars shown to magnitude 9.5. Created with Chris Marriott’s SkyMap software

I’ve included a detailed chart for tracking the little comet. Look for a dense, fuzzy patch of light. Hergenrother has a bright head and short tail fanning south. Through my 15-inch scope at low power it was miniature spectacle last night. Hergenrother’s nucleus mimicked a fuzzy, bright “star” at the north end of a well-concentrated coma; a wispy tail blew back from the comet’s head like.steamy breath on a cold day. Beautiful!

C/2011 L4 PANSTARRS on September 9 from Australia. The comet was 11th magnitude at the time. It’s currently best viewed from the southern hemisphere. Credit: Michael Mattiazzo

Tracking comets will develop your observing skills and help you to recognize subtle features like the density of the coma, whether the nucleus is star-like or fuzzy and the length and orientation of the tail. You can then apply these skills to future comet chasing to better enjoy and appreciate how the character of these icy beauties changes as they approach and recede from the sun.

There’s much to chase. Next March C/2011 L4 PANSTARRS could shine as brightly as Sirius and display a long, feathery tail. Then in November 2013 C/2012 S1 ISON will pass near Earth after a close flyby of the sun with a potentially spectacular show in store.