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Original Message
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UPDATE xyz:
This sky map shows Holmes' current position relative to nearby constellations:
[link to www.fourmilab.ch]
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UPDATE XIX, March 7, 2008:
The coolest Holmes pics ever:
[link to patrick.bornet1.free.fr]
[link to patrick.bornet1.free.fr]
:best!7P:
HEAVENLY ENCOUNTER: Great beauty can cause loss of balance, so before you click on this link, sit down. Done? That was Comet 17P/Holmes gliding by the California Nebula. The comet-nebula encounter is taking place right now--an easy target for backyard telescopes equipped with digital cameras. Photographers, after sunset, point your optics north at the constellation Perseus: sky map, ephemeris.
[link to www.spaceweather.com]
[link to spaceweather.com]
[link to spaceweather.com]
:coolest17P:
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UPDATE XVIII, March 6 2008:
HEAVENLY MEETING: High overhead after sunset, a heavenly meeting is underway. Attendees are Comet 17/P Holmes and the California Nebula (NGC 1499):
:HolmesinCa:
[link to www.spaceweather.com]
"Wow, what a lovely pair," says photographer P-M Hedén of Vallentuna, Sweden. To capture the giant comet (1o in diameter) and the even bigger nebula (more than 2o long) in a single frame, he used a wide-field WIlliam Optics WO66 APO telescope and a Canon Digtial Rebel XT. The scene will repeat itself for many nights to come, making this a good week for astrophotography: sky map, ephemeris.
[link to www.spaceweather.com]
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UPDATE XVII: January 11, 2008:
HOLMES AND ALGOL: In less than 10 days, Comet 17P/Holmes will appear to swallow the bright and famous star Algol. Last night in Fuerstenfeldbruck, Germany, Thorsten Boeckel photographed the pair converging:
[link to spaceweather.com]
More than two months after it exploded, "Comet Holmes can still be observed in dark areas with the naked eye. It is surprisingly easy," he says. "But near big towns the object becomes really hard to see."
For the next two weeks, finding Holmes won't be so difficult. Simply look straight up after sunset and locate Algol in the constellation Perseus. Comet Holmes is right beside it: sky map. A 60-second exposure with an off-the-shelf digital camera reveals the comet--no telescope required.
[link to spaceweather.com]
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UPDATE XV, 11.17.2007:
The initial dust ejection velocity was about 500 meters per second from the nucleus (similar to what was measured for comets Hyakutake and Hale-Bopp at their most active), but the outer zone of the coma is now increasing in radius at over 700 m/s. This is difficult to explain, but may be related to increased dispersion caused by the solar wind.
As of November 17, the central coma exceeds the angular size of the Moon; the entire coma is much larger than that. The physical diameter of the central coma is about 2.5 million kilometers, some 80% larger than the Sun. The coma of 17P/Holmes is now the largest object in the Solar System. Of course, "object" is used rather loosely here. While the coma appears very large and bright, it is also very tenuous. In the images, dim stars are easily seen right through it.
[link to www.cloudbait.com]
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UPDATE XIV; 11.1.2007:
Same visual size as the moon now:
:moonvsholm:
[link to spaceweather.com]
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UPDATE XIII,11.09.2007:
NEWS FLASH! "Is Comet 17P/Holmes losing its tail?" asks Italian astronomer Paolo Berardi. "Last night I recorded an image showing a big disconnection event that was not present on Nov 8th." See below:
:shedding:
[link to spaceweather.com]
[link to spaceweather.com]
Jack Newton of the Arizona Sky Village saw it, too. "The comet has a huge eruption moving along its tail. Holmes is more bizarre with each passing day."
[link to spaceweather.com]
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UPDATE XII:
[link to www.arksky.org]
Please see: [link to www.arksky.org] for daily updates, Oct. 25 through Nov. 5
Arkansas Sky Observatory (H45) update on Comet 17P:
Comet imaged in moonless skies, fair conditions
The comet has maintained steady brightness, both total and nuclear morphology has not
appreciably changed, and the overall size of the coma has grown considerably, as has the developing tail emerged vividly in P.A. 219 deg.
Coma overall diameter = 14.3' arc (CCD) with increasingly bright offset bright segment as well as possible tail to
SW of nucleus - in PA 219, the previous very bright "knot" of concentration has lessened drastically over the past 72 hours.
Coma appears very large and distinct to the naked eye, perhaps as much as 25 arc minutes
Magnitude, m1 = 2.4, (naked eye) nearly equal to previous night, very distinct cloud to the
naked eye with conspicuous nebulosity and NOW appears to have totally lost the previous distinct yellow color; comparison star (naked eye) is Alpha Per
Nuclear magnitude, m2 = 12.4, continues to drop rapidly as the nucleus becomes even more pinpoint
Overall color is nearly colorless, with slight yellow tint, throughout all expanses of the comet.
NOTE that the updated image at the end of the ASO sequence here, is in MONOCHROME size there is very little hue of color to the coma at this time.
Equipment: 0.4m SCT @ f/3 CCD, ST402-ME C-I CCD, RGB @ 8 seconds. Overall magnitude
estimate via naked eye, Alpha Per. by comparison.
[link to www.arksky.org]
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UPDATE IN BETWEEN:
Some more incredible jellyfish comet pics:
Here's the most recent and also the most spectacular so far:
[link to spaceweather.com]
More sheer craziness:
[link to spaceweather.com]
[link to spaceweather.com]
Earlie ones are to be found here:
[link to spaceweather.com]
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UPDATE XI, 11.06.2007:
COMET 17P/HOLMES: Italian astronomer Paolo Candy has christened Comet Holmes "the Jellyfish Comet." This picture taken Nov. 6th through his 8-inch telescope shows why:
[link to spaceweather.com]
"It has a green head and blue tentacles," notes Candy. An 8-hour movie recorded by astronomer Filipe Alves of Atalaia, Portugal, shows the tentacles in motion. Indeed, it seems to be swimming.
[link to spaceweather.com]
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UPDATE X, 11.05.2007:
COMET TAIL: Long exposures are starting to reveal the ragged tail of Comet 17P/Holmes. It took Michael Jäger eighteen minutes to record this view through his 8-inch telescope in Stixendorf, Austria:
[link to spaceweather.com]
The tail, which color photos show to be blue, looks like the aftermath of a terrific explosion. Indeed, Comet 17P/Holmes did explode on Oct. 23rd, brightening a million-fold to naked eye visibility. But the appearance of the tail is probably not a consequence of that blast. Why not? It's our point of view. Usually we see comet tails from the side and they make a long graceful arc through space. The tail of Comet Holmes, however, points almost directly away from Earth. Instead of seeing it from the side, we're seeing it end-on, resulting in its peculiar frayed appearance.
Everything about Comet Holmes seems a little peculiar--including the fact that anyone can see it. It's an "urban comet" visible to the naked eye among city lights as well as from the darker countryside. After sunset, look north for an expanding fuzzball in the constellation Perseus: sky map. The comet is about as bright as the stars of the Big Dipper and makes a fine target for both binoculars and backyard telescopes.
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We have another contradicting measurement of the diameter, it says 42' here which most likely comes closest to the truth. Now this means we have an approximate diameter of 3.3 million kms, more than the double size of the sun!!!
The comet tail is fan-shaped, with an aperture of about 90°. This is due to the small angle of the tail respect our line of sight (about 17°). The tail is best visible with a blue filter. The tail components are at position angles between 165° and 270°, extending from the optocenter at least 1°. The dust coma is 11' diameter and the gas coma is about 42'. Tech details: Schmidt Camera 300mm f/2.0 + CCD from a light polluted city. 1-2 november 2007, RGB 2.46 (2 nov) - 23.21 (1 nov) - 20.34 (1 nov) UT. Total exposure 3h46m, in frames of RGB 30:60:120 s each. Central dust coma elaboration with Larson-Sekanina 10°. North is up.
[link to spaceweather.com]
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UPDATE IX, 11.03.2007:
This is a composite image of exploding Comet 17P/Holmes. French astrophotographer Sebastian Voltmer combined various exposures taken through his 4.1-inch refracting telescope to highlight the comet's bright golden core (with jets and streamers), its gossamer green halo and an emerging faint blue tail. It's one of the strangest and most beautiful photos of a comet ... ever.
[link to spaceweather.com]
If that doesn't make you want to see Comet Holmes with your own eyes, perhaps this will: "The comet is growing fantastically," reports Thorsten Boeckel of Fuerstenfeldbruck, Bavaria, who has been monitoring the expansion: image. "By Sunday," he estimates, "it will be half as wide as a full Moon."
[link to spaceweather.com]
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UPDATE VIII, 11.02.2007:
"Clearly seen here are delicate internal rays, a bright jet, and a brilliant sunshine-yellow core," he says. "The comet's outer envelope is a stunning emerald color."
[link to spaceweather.com]
The jets and rays, reported now by a growing number of photographers, remind us of the fantastic explosion that took place on Oct. 23rd when Comet Holmes increased in brightness a million-fold in less than 24 hours. Ever since, the sunshine yellow core has been expanding--fed by jets? Or driven by the momentum of a blast that no one saw until it was over? No one knows. The underlying cause of the explosion and current events at the core remain a mystery.
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UPDATE VII:
Gas Eruptions from Comet Holmes?
October 31, 2007 Fort Branch, Indiana - Today I received the following email from amateur astronomer Charlie Kiesel who lives in Fort Branch, Indiana. He has sent the images of Comet Holmes seeming to erupt in two of 28 images Charlie photographed on Sunday night, October 28, 2007, at 9:59:38 PM CDT and 10:06:51 PM CDT. Charlie has sent the "erupting" images to Spaceweather.com and other NASA comet websites for comment. He told me, "Comet Holmes flared up from a magnitude 17 to magnitude 2 in just 24 hours from October 24 to 25, 2007."
:holmesgas:
Saturday night, October 27, 2007, my wife was looking at the comet through 7 X binoculars and was sure she saw something move off and away from the comet. I didn't think much of it at the time, but the next night (Sunday, October 28), I took about thirty photographs of the comet--timed exposures of 7- 15 seconds with a Sony H1 12 X optical lens (camera specs in File/Folder Info below). I recorded two photos with something seemly being ejected from the comet or from some pieces of it which may have been blown off and to the front of the comet and then exploded into view briefly on their own.
[link to www.earthfiles.com]
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UPDATE VI, 11.01.2007:
GIANT COMET: Comet 17P/Holmes has been relentlessly expanding since its explosion on Oct 23rd and now it spans an angle in the sky almost half as wide as the full Moon. Using a picture of the comet he took on Oct. 30th, Helmut Groell of Moers, Germany, created this animation for comparison:
[link to www.spaceweather.com]
Actually, the comet is even bigger than it looks. While the Moon is a mere 240 thousand miles away, Comet Holmes is 150 million miles from Earth. The comet's physical diameter is thus seven times wider than the planet Jupiter--and it is still expanding.
Anyone with a backyard telescope can watch it grow. After sunset, point your 'scope at the 3rd-magnitude fuzzball in the constellation Perseus: sky map. Finding the comet is no problem. The only question is, will it fit in the eyepiece?
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UPDATE V 10.30.2007:
"Now that the diameter of Comet 17P/Holmes has increased so dramatically, finding it is child's play," says Laurent Laveder of Quimper, France. "Even my daughter and my stepdaughter know where to find it!" Last night, he took this picture of the girls pointing the way:
[link to spaceweather.com]
One of the many curiosities of Comet Holmes is the lack of a normal comet's tail. Since it exploded on Oct. 24th, Holmes has been almost perfectly spherical, more like a planet than a comet. Now, however, a tail may be emerging.
"On Oct. 28th, I decided to take many short exposures to try to detect any hint of an ion tail," says Sean Walker of Chester New Hampshire. "Success! Note the faint, diffuse tail trailing off to the upper-left in this image:"
[link to spaceweather.com]
The emerging tail is even more distinct in a photo taken Oct. 29th by Pete Lawrence of Selsey, UK. "This is a 45 minute exposure (9x5 minute exposures) through my Vixen 4-inch refracting telescope," he explains. "The tail is extremely faint but is there heading off to the upper right of the coma. As the Moon moves out of the way, astrophotographers will have a better opportunity to focus on the faint structures that constitute that most important piece of a comet - its tail!"
Readers, this comet is as bright as the stars of the Big Dipper, which makes it an easy target for backyard telescopes and off-the-shelf digital cameras. Point, click, and submit your images to Spaceweather.com!
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UPDATE IV 10.28.2007 about 8:00 AM EDT:
Exploding Comet 17P/Holmes is now larger than Jupiter. Astronomer Eric Allen of Quebec's Observatoire du Cégep de Trois-Rivières combined images he captured on three consecutive nights (Oct. 25, 26 and 27) and placed them beside a picture of Jupiter scaled to the same distance as the comet:
[link to spaceweather.com]
The diaphanous and curiously spherical cloud surrounding the comet's core is now large enough to swallow the King of Planets! It's gotten so big, in fact, that many observers say they can see it without a telescope. "I estimate the comet's brightness at magnitude +2.2 and last night I could see the disk easily with the naked eye," reports Martin McKenna of Maghera, Northern Ireland. "I saw the disk, too," says Doug Zubenel of Lincoln County, Kansas. Bill Smith of puts the comet "at magnitude +2.1--nearly as bright as Polaris"--and notes that "to the naked eye, it is no longer a simple point of light." [sky map]
What would make a comet explode in this fashion? Actually, a better question is, what would make a comet explode twice in this fashion? This is the second time Comet 17P/Holmes has erupted. The first was in 1892, an outburst that led to the comet's discovery by British astronomer Edwin Holmes.
The answer may be sinkholes. There is growing evidence that some comets and asteroids may have a porous internal structure akin to, say, swiss cheese or a honycomb. Suppose one of the chambers of the honycomb suddenly collapsed, exposing many square kilometers of fresh cometary ice to sunlight for the first time. A flurry of sublimation would ensue with mega-jets of dusty gas emerging from the sinkhole to create a cloud around the comet much as we see now. Twice = two sinkholes, one in 1892 and one in 2007.
Because no one can see the comet's nucleus--it is small, far away and hidden inside a Jupiter-sized debris cloud--this "explanation" is no more than conjecture. The true events at the core of Comet Holmes remain unknown. Grab your telescope and savor the mystery!
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UPDATE III 10.27.2007:
A gaseous cloud is racing away from the comet's core almost doubling in size from night to night. This sequence of images was captured by Wah! of Hong Kong using a Meade 8-inch LX200 on Oct 25th and 26th (details).
[link to spaceweather.com]
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UPDATE II 10.26 ~ in the evening EDT:
[link to spaceweather.com]
The gaseous cloud surrounding the comet's core has more than doubled in radius during the past 24 hours. "I captured these images on consecutive nights using the same equipment (a 14-inch LX200 GPS) and similar exposure times (1x10s)," says photographer Eduardo Hernandez of Torreon, Mexico. This follows an even more astonishing million-fold increase in brightness on Oct. 23th.
What is happening to this comet? It remains a mystery.
It's a mystery you can behold with your naked eye. Step outside after sunset, face north, and look for the extra "star" in the thigh of Perseus: sky map. Comet Holmes is similar in brightness and appearance to the stars of the Big Dipper, very easy to see. If expansion of the spherical cloud continues, Holmes could soon become a naked eye disk rather than a dimensionless point of light. Stay tuned!
UPDATE, 10.26.2007, before noon:
STRANGE COMET: Astronomers around the world agree, Comet 17P/Holmes is one of the strangest things ever to explode in the night sky. It's a comet, yet it looks like a planet with a golden core and a green atmosphere:
[link to spaceweather.com]
Chris Shur of Payson, Arizona, took this picture last night using his 12.5-inch telescope and a Canon XTi digital camera. "The comet was yellow and green, very bright in the viewfinder," he says.
Yesterday, Comet Holmes shocked sky watchers with a spectacular eruption, brightening almost a million-fold from 17th to 2.5th magnitude in a matter of hours. The comet is now visible to the naked eye--even from light polluted cities--high in the northern sky after sunset: finder chart.
The golden hue of Holmes' core is probably the color of sunlight scattered by comet dust, while the green fringe likely signifies an atmosphere rich in diatomic carbon and cyanogen (substances found in many green comets). There are reports that the fuzzball is expanding and taking on a lopsided shape--the first signs of a tail? Amateur astronomers are encouraged to monitor developments. After sunset, point your backyard telescope at the extra "star" in the thigh of Perseus.
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10.25.2007:
Comet 17P/Holmes has brightened by a factor of five hundred thousand or more during the past 24 hours !!!
Astronomers in Japan, Persia and Europe report that Comet 17P/Holmes is undergoing a spectacular eruption. The 17th magnitude comet has brightened by a factor of five hundred thousand or more during the past 24 hours becoming a naked-eye object in the evening sky. Look for a yellow 2.5th magnitude fuzzball in the constellation Perseus after sunset. [sky map] [ephemeris] [3D orbit]
"This is unbelievable!" says Iranian astronomer Babak Tafreshi. "I was amazed to find Comet Holmes so easily with the naked-eye in the light-polluted skies of metropolitan Tehran." Click on Tafreshi's photo to pinpoint the comet:
[link to spaceweather.com]
The outburst may signify a breakup of the comet's core or a rich vein of ice suddenly exposed to sunlight--no one knows. At present the comet looks more like a star than a comet; it does not have a discernable tail, but it might grow one as the outburst continues. Amateur astronomers are encouraged to monitor developments using binoculars and backyard telescopes. Stay tuned for updates!
[link to spaceweather.com]
17P/Holmes
Surprisingly, a great outburst occured on Oct. 24 and now it becomes so bright as 3 mag, visible with naked eyes! Completely stellar, so it looks like a nova. It was observed as 14.5 mag in July, then it had been fading down to 17 mag until mid October as predicted. This comet was also in great outburst at the discovery in 1892 and became so bright as 5 mag. At that time, the comet faded after the first outburst, but soon brightened again in the second outburst. The further brightness is uncertain. But the comet will be observable in excellent condition for a while after this.
[link to www.aerith.net]
[link to www.aerith.net]
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