COMET HOLMES! IT'S HOT! IT'S BIG! IT'S NOW! Vleeptron's FAQs -- Reliable Science Info 100% Guaranteed UnPerverted by the Bush White House!

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Top image:

Comet Holmes finder chart

Periodic Comet Holmes (17P) is located in east-central Perseus. Although this finder chart shows the northeastern horizon at dusk, the comet will be easier to spot later in the evening when Perseus is higher.

Bottom image:

Comet Holmes from my Hood

At Williams College in Williamstown [northwest corner of] Massachusetts, Steven Souza writes: "Our students observed it last night (October 25th). This image was taken with a 0.6-meter DFM Cassegrain scope and Apogee Alta U9000 CCD camera, unfiltered, with an exposure time of 0.1 second. There's obvious and asymmetric structure to the coma, which is (at about 0:47 UT October 26th) about 2.3 arcminutes across — similar in size to the Ring Nebula, M57."

Photo by Huajie Cao, Adam McKay, Steven Souza

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Okay, this is all new to me, but apparently Comet Holmes (officially known as 17P) is blossoming and erupting into one of the brightest, largest visitors ever to cruise the night skies near Planet Earth.

I filched all this stuff from Sky & Telescope Magazine, 'cause they've been writing reliably about crap in the sky for about a century, and no one has ever accused them of lying or intentionally misleading people about Scientific Things for political reasons.

Notice I did NOT link you to or filch anything from the Bush White House or any agency of the US Government, like a FEMA press conference, or sworn testimony about global climate change from the head of the US Centers for Disease Control (an M.D. doctor, I don't know what her specialty is, maybe you should take your sick kid to some other doctor).

My experience bumbling around the Heavens suggests that a comet is a northern/southern hemisphere-specific thingie, and Holmes is putting on its show in the Northern Hemisphere. So people in the Southern Hemisphere -- Australia, New Zealand, South Africa, South America -- might not get much of a show or any show.

But that's just the best guess from the Vleeptron Space Academy. If you're getting a whale of a show from Madagascar, please Leave A Comment.

But if you're in North America, Europe or most of Asia -- GO OUTSIDE AT NIGHT! Call the local university Astronomy Department and ask which direction to point your binoculars in!

If it's really going to be as big and bright and spectacular as this dump from the USA magazine Sky & Telescope is ballyhooing, a good pair of binoculars is probably the best thing you can use to see Comet Holmes. Reserve a fancy telescope for trying to take photographs. And whatever you do, THIS IS A WRONG MOMENT TO RUN OUT AND BLOW $$$$ ON AN EXPENSIVE TELESCOPE!!! If you must blow money on something in a hurry, invest in some really good binoculars, perfect for the comet and nature stuff and cheerleader practice across the street.

But remember last year's Comet McNaught over South Africa? Vleeptron's Comet Correspondent in Cape Town shot wonderful, amazing comet photos with an ordinary digital Ph.D. camera! (Ph.D. = Push Here, Dummy.)

I just hosed up everything about Comet Holmes in S&T. You'll have to make Geek Sense of it as best you can. Please Leave A Comment if you see the Comet, or if you have a Question.

VLEEPTRON SPACE ACADEMY
FREQUENTLY ASKED QUESTIONS
ABOUT COMET HOLMES 17P

Q. Which direction should I look?

A. Up. Almost all comets are best seen by looking up.

Q. When is the best time to see the comet?

A. Night. Not day. When the Up Sky is Very Dark. My buddy said he saw it about 30 minutes before midnight. That was local New York City USA time.

If you're in Bucharest or Tel Aviv -- how the hell do I know? Don't they teach astronomy at the university there?

Q. Well, "Up" is certainly helpful. But then where should I look?

A. START by looking toward the NORTHEAST. If you're looking up and northeast and you DON'T see a big, bright, strange, creepy, unusual thing that you've never seen in the sky before, slowly turn your toes to the right and keep looking up. Keep turning your toes to the right until you return to the direction you began.

If you still don't see a big, bright, unusual object in the night sky, is the sky clear, or full of dark clouds? Are you in the Northern Hemisphere? Are you on the surface of Planet Earth?

If you're a lefty, you can turn your toes to the left.

Q. Why didn't somebody tell me this comet was coming?

A. They did. You just weren't paying attention. What do you usually do when it's dark? Hang in a pub or a bar or a club?

Comet Holmes is one of those periodic comets that passes by Earth regularly, exactly like clockwork. Since Halley, elliptical, periodic Comets just aren't surprises anymore.

Well, maybe they're surprises for you. Can you really meet cool people in bars? Good conversationalists?

Q. Does the appearance of this bright, large comet mean that somewhere on Earth, a very important person will die, or a very important person will be born, or a very important battle will take place, and one side will win the battle, and history will be changed? Does this comet mean there will be a big change in the stock market?

A. Yes.

Q. Is this a good time for me to get married?

A. Yes! Hurry! You don't have much time! Get married while Comet Holmes is still in the night sky!

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Sky & Telescope
Monday 29 October 2007

Comet Holmes Stays
Bright, Enlarges
in the Evening Sky

Amateur astronomers the world over have been stunned and amazed by the weirdest new object to appear in the sky in memory. And it's one of the brightest, too.

For the most recent news, see the daily updates at the end of this article.

Less than a week ago Periodic Comet Holmes (17P) was a tiny, roughly 17th-magnitude nonentity out between the orbits of Mars and Jupiter. Then on Wednesday, October 24th, skywatchers looked up to see a bright new yellow-orange "star" shining in Perseus. For no apparent reason, the comet had brightened about a millionfold to shine at close to magnitude 2.5. That made it plain to see even in the bright moonlight and through all but the worst light pollution. It looked truly starlike; even high telescopic magnification barely resolved it as anything larger at first. But within a day it had expanded into a perfectly round, bright little disk with a tiny nucleus as seen in binoculars and telescopes. It looked like no comet ever seen.

Its startling outburst, however, has a precedent. The comet was also in a major eruption 115 years ago, in November 1892, when English amateur Edwin Holmes was the first to spot it. It reached 4th or 5th magnitude, faded in the following weeks, and then underwent a second eruption 2 1/2 months after the first. (The comet's history.)

Comet through full moonlight, 25 October 2007

Observers worldwide had no trouble spotting Comet Holmes through the full moonlight on the evening of October 25, 2007. Shigemi Numazawa took this very wide-field shot from Niigata, Japan. Click image for larger view.

Shigemi Numazawa
The Outburst. The first person to notice something happening this time, according to IAU Circular 8886 (issued October 24th by the Central Bureau for Astronomical Telegrams) was A. Henriquez Santana at Tenerife, Canary Islands, shortly after midnight on the morning of [24 October] local time. The comet was then about 8th magnitude, but within minutes Ramon Naves and colleagues in Barcelona, Spain, caught it at magnitude 7.3.

Internet discussion groups came alive with the news. "To my amazement, 17P had brightened to naked-eye visibility," exclaimed Bob King when he spotted Comet Holmes shortly before dawn in Duluth, Minnesota. "What a sight!" he posted to the Comets Mailing List. Alan Hale of Cloudcroft, New Mexico, concurred. To Hale (well-known codiscoverer of Comet Hale-Bopp) it appeared essentially starlike in a telescope until he switched to high power.

Then things only got better. As Earth continued to turn, nightfall arrived in Japan. "It is visible with naked eyes in a large city!" posted Seiichi Yoshida, who observed the comet from beside Tsurumi River in Yokohama. By 17:15 Universal Time he was describing Comet Holmes as magnitude 2.8.

Since then the comet has remained just as bright or even a little more so — shining as the third-brightest "star" in Perseus — while enlarging substantially. It's still a round, sharp-edged disk with a bright core in binoculars and telescopes. Comet expert Gary Kronk expects Comet Holmes to remain bright and continue to enlarge in the coming days, as it makes its way slowly westward across Perseus. Its position on 25 October (0h UT) was

right ascension 3h 53m
declination +50.1° (equinox 2000)

and by October 30th it will have moved only slightly, to 3h 48m, +50.4°. On November 19–20 It will pass closely by Alpha Persei (by 1/3°).

For skywatchers in the Northern Hemisphere, Perseus is visible all night around this time of year. The comet will stay in Perseus all the way into next March.

See pictures. And submit yours to S&T's online gallery!

Chart and ephemeris of the comet's future motion. Light curve (scroll down).

This 12-arcminute-wide frame from Arkansas Sky Observatory shows the comet as a brilliant, near-circular disk on the morning of October 25th. Clay Sherrod used a 0.4-meter (16-inch) Schmidt-Cassegrain telescope at f/3.
Clay Sherrod / ASO

Thursday 25 Oct: "This object is amazing!" posted Brian Cudnik of Houston, Texas, on the Yahoo CometChasing group after coming in from his telescope on the evening of the 24th. "I have just observed it with an 8-inch f/10 Cassegrain, boosting the power up to 163x then to 508x.... The bright inner coma seems displaced off-center toward position angle 315°. The inner coma opens up into a fan toward position angle 300°, and I have noticed one ripple, akin to the hoods/ripples seen in Comet Hale-Bopp ten years ago. The coma is uniform in brightness, aside from this fan-shape material emanating from the central condensation, and has a well-defined edge." He measured the coma to be 69 arcseconds wide using using the drift method. "The entire object has a nice yellow-white color; no sign of any tail. The apparent magnitude is +2.8 (estimated using Alpha Per at +1.9 and the other two bright stars adjacent to it at +3.0 each) and has remained rather steady all evening."

Posted Dan Laszlo of Fort Collins, Colorado: "In an 18-inch Newtonian at 90x, the yellow orb is like a bright spherical planetary nebula. Diameter of the bright portion is about equal to the lunar crater Tycho, so magnification helps. I can detect a very faint spherical outer envelope, about equal in radius to the diameter of the bright portion, tough with the moonlight."

From Florian Boyd, Palm Springs, California: "I think this is about the most amazing thing I've ever seen in the sky!"

Despite moonlight and smoke from wildfires near Los Angeles, Anthony Cook captured the comet at the prime focus of Griffith Observatory's 12-inch Zeiss refractor at 8:30 UT on October 25th. This frame, cropped to 4 arcminutes wide, shows the comet's nucleus slightly off-center in the larger coma. In longer exposures the coma had a well-defined edge, allowing Cook to measure its growth rate. He got a diameter of 86 arcseconds at 7:46 UT, then 89 arcseconds an hour later.
Griffith Observatory / Anthony Cook

Friday, Oct. 26: Last night S&T's Alan MacRobert wrote: "Omigod. Through thin clouds lit by the full Moon I had to guess where Perseus was, but I swept around with 10x50 binoculars from my front step, and wham, there was the comet! It's sure isn't starlike now, at least not in the 10x binocs (with homemade image stabilization). It's a very sizable bright fuzz spot, perfectly round, with a large, brilliant, hazy nucleus and a very sharp edge to the circular coma. It's yellow with just a hint of green.

"When the clouds finally cleared and I could see it with the naked eye, it was still starlike to my vision. Magnitude 2.7, based on Alpha Persei being mag. 1.9 and Delta Persei mag. 3.0. You just look up and there it is. It's the brightest 'star' in Perseus after Alpha Per and Algol."

Comet Holmes at high power, Oct. 25, 2007

At Williams College in [Williamstown in the northwest corner of] Massachusetts, Steven Souza writes: "Our students observed it last night (October 25th). This image was taken with a 0.6-meter DFM Cassegrain scope and Apogee Alta U9000 CCD camera, unfiltered, with an exposure time of 0.1 second. There's obvious and asymmetric structure to the coma, which is (at about 0:47 UT October 26th) about 2.3 arcminutes across — similar in size to the Ring Nebula, M57."
Huajie Cao, Adam McKay, Steven Souza

Later that night: "Used the 12.5-inch reflector at 75x, 110x, and 180x. A brilliant, starlike, white nucleus is dead center in the perfectly round coma. What looked like the nucleus in the binoculars is an inner coma or broad fan offset from the nucleus toward the southwest. At these magnifications the bright round disk is no longer perfectly sharp-edged, but still pretty nearly so. It also has a slight but definite ring appearance, as if some of the light is coming from a hollow, spherical, glowing shell. Farther out beyond this is a much dimmer round glow with about twice the diameter of the bright disk. Only out this far does the brilliant skylight of the perigean full Moon in this part of the sky begin to matter. This was at 1 a.m. EDT (5:00 UT) October 26th with the comet (and Moon) near the zenith. Still magnitude 2.7 naked-eye."

Comet Holmes at October 27.31 UT
It's enlarging daily. P. Clay Sherrod took this CCD image at 9:55 UT October 27th, using a 16-inch Schmidt-Cassegrain telescope at f/3 for a 5-second RGB composite exposure.
P. Clay Sherrod

Saturday, Oct. 27: Last night the comet was as bright as ever; various people's estimates averaged magnitude 2.5 early in the night (time zones of the Americas). Its overall form in a telescope has not changed, just enlarged a lot (animation by Wah). Writes P. Clay Sherrod, who took the image at right: "Even more incredible each night. The comet now measures 255 arcseconds across (via CCD [Charged-Couple Device, a solid-state device used for high amplification of faint light signals] direct measure). On October 25, similar measures of the coma revealed diameter of approximately 121 arcseconds." View the comparison.

Sunday, Oct. 28: By last night the comet had enlarged to 348 arcseconds (6.3 arcminutes), as measured by Clay Sherrod on his CCD images. "It's beginning to look a bit nonstellar to the naked eye," writes Alan MacRobert. "Not as crisp and sparkly as Alpha and Delta Persei."

Comet Holmes on the night of Oct. 27–28, 2007

All of the comet's features that are visible in the eyepiece of a telescope are captured in this image by Sean Walker. The bright yellow-white coma is dust lit by sunlight; the green halo is fluorescing gas (the green emission is mainly from C2 and CN molecules). Walker used a 108mm F/4 Faworski Astrograph and a Canon 10D camera. This image is a stack of ten 30-second exposures and (to bring out the nucleus) ten 6-second exposures. Click image for larger view.
S&T: Sean Walker

Within a few more days the nonstellar appearance ought to be obvious, making this object more of an attraction for the non-astronomical public. Hold a star party, and alert your local news media!

"When I first saw it, I thought it looked like a frosted incandescent light bulb on a dimmer switch," commented Mike Foreman of Carrollton, Texas, on the Comets Mailing List.

Using Alpha and Delta Per as comparisons (magnitudes 1.9 and 3.0), MacRobert estimated the comet to be magnitude 2.8, just a trace fainter (more similar to Delta) than two nights ago. In stabilized 10x50 binoculars it looked just the same as before only bigger, with all its details easier to see.

Monday, Oct. 29 (by Alan MacRobert): Last night the comet was very plainly a little disk to the naked eye rather than a star. Definitely a more interesting naked-eye view now! No change in brightness in the last 24 hours. In fact, the average of all good magnitude estimates has basically stayed flat since the outburst. (Light curve.)

Finally, the bright round disk is starting to show some asymmetry. In the 12.5-inch scope at 75x, the disk's northeast edge — the side away from the bright fan near the nucleus — is looking more compressed and sharp-edged than the southwest edge, which is a bit vaguer. The slightly darker 'moat' inside the disk's edge is better defined on the northeast side too.

The fan southwest of the nucleus seems more diffuse now. The nucleus itself is fuzzier too, no longer so starlike. This was easy to judge tonight because an actual orange star, roughly as bright as the nucleus, was shining right through the disk!

Even in the waning-gibbous moonlight, the dim, diffuse, outermost glow of gas was a little more than twice the diameter of the bright disk of dust. All this was around 12:25 a.m. EDT (4:25 UT) October 29th, right after the Sox won the World Series. I'm sure I wasn't the only one running back and forth between the telescope and the baseball game — just like the last time the Sox won the [baseball World's] Series, in 2004 in the middle of a total lunar eclipse.

Future prospects. The comet is likely to stay bright for many days or weeks. The yellow color is dust reflecting sunlight, as confirmed by the spectra that have been taken. Dust is what keeps a comet bright — as opposed to gas (comet gas is green and blue), which blows away quickly in the solar wind. This comet won't fade out soon.

Any tail will probably be short and stubby when, or if, it forms. The tail should be pointing nearly away from us in space — we're looking down its length — since the comet is nearly on the opposite side of Earth from the Sun. From the comet's viewpoint, the Earth and Sun are only about 15° apart, and this phase angle will stay small for many months. So we'll keep looking down the tail.

- 30 -

Posted by the Editors of Sky & Telescope, October 27, 2007

comments (72)
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Holmes Outburst
Posted by Duncan Parks October 24, 2007 At 11:06 PM PDT
This one is really rewarding in the telescope, even in urban skyglow. At 72x, it showed a broad, round coma, with a notably bright streak smearing out from a very bright nucleus. Seen from Portland, OR, 10/25, 9:15 pm PDT, 10-inch Dob. We're really lucky to have a clearish night here in October!

Comet Holmes Outburst
Posted by David Knisely October 24, 2007 At 11:31 PM PDT
Well, I got a better look in my Nexstar 9.25 (0600 UT on Oct. 25th). The comet has a very faint outer halo perhaps four or maybe five arc minutes in diameter. Inside this is a *brilliant* inner coma around 1.5 arc minutes in diameter with very well-defined edges. At 297x, the core showed a small star-like point when the seeing settled with a diffuse conical fan-like brightening flowing away from the nuclear condensation roughly in the anti-solar direction. The edge of the coma seems to show a somewhat shell-like feature, as if the outburst generated a bit of a shock front. The comet is very similar in brightness to Algol (very slightly fainter), so it is probably around magnitude 2.3 to 2.5 or so. I hope it hangs in there for a while!

Comet Holmes (17P)
Posted by Indigo_Sunrise October 25, 2007 At 09:40 AM PDT
Is it known why the comet has brightened so much? I don't know much about comets, asteroids, etc., but is it because of the mineral or elemental make-up of the comet causing it to brighten as it comes in close proximity to the sun? I'm hoping it clears up here at my location (MD), so that I can have a chance to view it before it's gone. Which brings me to another question: how long is Comet Holmes expected to be visible?

rain, rain...
Posted by Todd Vance October 25, 2007 At 10:05 AM PDT
gee--can you guys do something to make sure the comet is still there when the clouds clear and I can actually look? If not, I have to ask The Weather Channel to move the clouds away a little faster :) All this time, no rain, and now that there's a comet, the Washington, DC area is all clouded over and it rains like in a rainforest or something.

Reasons for Outburst
Posted by Bryan Seigneur October 25, 2007 At 10:16 AM PDT
IANAAstronomer, or planetologist. However, from reading pop journals, I get the idea that we don't know a lot about the make up or behavior of comets. One fact is that their orbits move them between extremes. They go from solar altitudes that are near absolute 0 (0K), where methane and many other compounds we think of as gaseous are slowed down and even crystalized, and they swing all the way down to the inner solar system, where things are as we know them, or even hotter. This can understandably wreak havoc on a poor little planetoid. I assume this havoc of heating, evaporation, an d shifting is seen in the cometary tail. I think it would not be foolish to imagine that any small object like Pluto et al would do similar things if its orbit were magically made wildly eccentric like that of a comets. I'd say the object would then actually be a comet for all intents. Another fact is that comets change. Think about all the matter that is blown away from a comet, or violently shifted, during its foray into the inner solar system. Then, as it leaves the warm bosom of the sun, things fall back down and freeze solid, but not *at all* necessarily in the same place. If it comes through one time and does one thing, it may do something totally different the next time. So, we were just lucky enough to spot a comet during a particularly violent warming event.

holmes
Posted by matthew burmeister October 25, 2007 At 11:42 AM PDT
i hope that i can see this in my 90mm goto!

Comet likely brightning?
Posted by Garret Moore October 25, 2007 At 01:20 PM PDT
I'm an astronomical and science illustrator and have illustrated many comets based on speculative science. In the 80's I did my first multiple comet illustration after observing many single nuclei and speculating this could happen. Shoemaker-Levy was the first recorded, so I was ecstatic. So, thinking about this for some time now. I am speculating that the comet could be breaking up and will slowly spread as it is influenced by planetary or solar gravitational. The brightening could be the result of more surface area exposed in the break up. Depending on how it fractioned and warming it could multiply its output my many multiples. Could this be another Shoemaker-Levy? I will go to the software (SNP)to see its track and estimate it's probable effects. I'll be looking to reports here of any observed separation or displacement of the nuclei or dramatic shape changes in the coma. I will observe tonight, but without a collimator my 17" Dob will be close to useless. Especially in city sky's

Comet 17P Holmes
Posted by Kent Blackwell October 25, 2007 At 01:48 PM PDT
When I returned home from the movies on Wednesday night, October 24 it was raining. Suddenly the sky temporarily cleared long enough for me to set up my 80mm and 100mm refracting telescope to view the outburst of Comet 17P Holmes from my home in light-polluted Virginia Beach, VA. At 30x in the 80mm the comet closely resembled the reddish colored planetary nebula IC 418 in Lepus. The red color vanished at higher power, nor did it show in the 100mm telescope, although that instrument revealed more inner detail. As I was connecting A/C power to the motor-driven equatorial mount of the 100mm the rain returned so I had to drag everything quickly back into the garage. An hour later the skies cleared long enough for me to set up my 10" f/4.7 Dobsonian. Wow! At 175x Comet 17P Holmes resembled the large planetary nebula IC 1535 (Cleopatra's Eye) in Eridanus, only much brighter! The core was exceedingly bright and slightly elongated towards the south. What a great surprise! What a great comet! Don't miss it. Kent Blackwell Virginia Beach, VA

Could this be caused by an Impact.
Posted by Marshall Eubanks October 25, 2007 At 05:45 PM PDT
I would suspect that the most likely reason for the outburst was that it was hit by a meteor. It will be interesting to see if it was disrupted. Let's do a back of the envelope sanity check. This looks like considerably more material than came from the "Deep Impact" impactor, which left a 100 meter crater. If Comet Holmes is about the same size as the comets wit known sizes, the exposed surface area is about 100 square km. Assume that the Martian cratering rates apply; there are 200 similar comets, and each is obseved for something between a few months and many years. That is maybe as much as 100,000 years of comet observations and, using the standard Martian crater model at http://www.psi.edu/projects/mgs/cratering2.html you can see that the expected crater size in that period for 100 square km is about 30-50 meters (i.e., smaller than the Deep Impact crater). There is thus roughly a 1% chance of forming a 100 meter diameter crater in our observation history, and a pretty small chance of a much larger crater being formed in any comet observed in modern times. So, I conclude that it is unlikely that this is is due to a meteor impact, unless there is something wrong with my BOE calculations

cOMET hOLMES
Posted by LOUIS wELKE October 25, 2007 At 06:47 PM PDT
ON 10-25-07 AT 8: 30 PM I began observing Comet Holmes with my Meade 8' LX90 USING a 26 MM 2" eyepiece and tracking the comet just above the star Capella and a little to the south. I then tried a 2" 16.5mm eyepiece and then went to a 5mm 1.25 eyepiece at 400X it was huge but it had lost resolution so I went back to a 26mm 2" eyepiece that produced 77X. This is a beautiful comet to watch. Lou Welke

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