A small and (normally) very faint comet surprised observers around the world last night by suddenly becoming bright enough to be seen quite readily with the unaided eye. Comet 17P/Holmes, which was discovered back in November 1892 by Edwin Holmes, from London, England, was no brighter than magnitude 17 a couple of nights ago — about 25,000 times fainter than the faintest star that can normally be seen without any optical aid. In order to view an object this faint, one would need a moderately large telescope.

But the comet’s brightness has suddenly rocketed all the way up to third-magnitude, brightening nearly 400,000-times in less than 24-hours! The comet appears visually to the eye as a fuzzy, albeit distinct, starlike and yellowish object, but with no noticeable tail. The comet is currently located among the stars of Perseus, which can be found about halfway up in the northeast part of the sky as darkness falls. Perseus is almost directly overhead by around 2 a.m. local daylight time and is still well up in the northwest sky as dawn begins to break. According to an E-mail just received from Seiichi Yoshida of Japan, “Perseus does not look like the Perseus that is familiar to us [anymore] due to the bright stellar object there now.”

A celestial question mark

Why Comet Holmes has undergone such an explosive outburst is not understood. What is amazing is that it made its closest approach to the Sun last May, but came no closer than 191 million miles (307 million kilometers) to the Sun. The comet is now moving away from the Sun and currently is quite far out from Earth at a distance of 151 million miles (243 million kilometers).

This comet is part of Jupiter’s “family” of comets — a group of comets where the far end of their respective orbits (aphelia) cluster around the orbit of Jupiter — and takes 6.88 years to make one circuit around the Sun. So why would a comet far out in the cold of space suddenly brighten hundreds of thousands of times? What is the source of such energy? Does it come from within the comet or without? The outburst may signify a breakup of the comet’s core or a rich vein of volatile ices suddenly exposed to sunlight–no one knows.

Comet Holmes is not alone in exhibiting anomalous effects. In the past, other comets have undergone unexpected outbursts in brightness. And this is probably not the first outburst for Comet Holmes: when it was discovered in 1892, it was likely in outburst, since it became as bright as fourth magnitude and was dimly visible to the naked eye. According to comet expert, John Bortle, ” . . . the parallels between the current outburst of P/Holmes and the 1892 event are quite extraordinary. Following the initial stages of the 1892 outburst, the comet’s total magnitude faded only very slowly and it remained visible to the unaided eye for about 3 weeks. During this interval the coma expanded dramatically (as might be expected). One can anticipate that the same general evolution will occur this time.”

Bortle adds: “I would also call observers’ attention to the fact that P/Holmes underwent a second outburst (something that has been observed in conjunction with several other outbursting comets), of almost equal amplitude to the first one, about 75 days following its 1892 November brightening. Thus, I would urge everyone to watch very carefully for a possible repeat of this secondary event about the turn of the year.”

Because of occasional close approaches to Jupiter, the orbit of Comet Holmes has been altered a few times . . . in fact the comet was considered “lost” for nearly 60 years before it was finally recovered with a large observatory telescope in 1964. As to what this object will do in the coming days and weeks is not known. The brilliant light of the waxing Moon will be a hindrance for the rest of this week, but if you have binoculars or a small telescope, you might want to try seeing what certainly is one of the solar system’s most enigmatic objects!

Check out the SKYMAP:

– Joe Rao, Farmers’ Almanac Astronomer

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comet, comet Holmes, astronomy happenings, perseus

by sduncan
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ORIONID METEORS TO PEAK SOON . . . BRIGHT DISPLAY IN THE OFFING?
From Joe Rao, Farmers’ Almanac Astronomer

This is an alert for all observers to watch for a possible unusual display of Orionid meteors. The Orionids are thought to result from the orbit of Halley’s Comet; some of the dust shaken from this famous comet as it runs its gigantic orbital loop from the Sun out to the orbit of the planet Neptune; a part of the same permanent river of meteoroids following the comet. Discovered in 1864, the Orionids were not linked to
This is actually our second encounter of the year with this rubble river. In early May we meet them on their way outward from their nearest approach to the Sun. The result is the Eta Aquarid meteor shower.

In October we encounter the part of the meteor stream moving inward toward the Sun. The orbit is in fact a retrograde one — moving opposite or contrary to our orbital direction of motion. That explains why the Orionids hit our atmosphere at a very high velocity — 42 miles per second — slower only than the November Leonids.

Another characteristic of the Orionids is that they start burning up very high in the atmosphere — probably because they are of lightweight material. This means they come from the diffuse surface of the comet, and not its core. Some Orionids are fireballs, but most are faint, and about 20-percent leave trains that persist for one or two seconds. Orionids meteors can be found between October 2 and November 7.

Traditionally, the peak of the Orionids comes on the morning of October 21, with an average hourly rate of about 25. Orion, now ahead of our journey around the Sun, doesn’t rise until 11:00 p.m., and the greatest number does not occur until around 4 or 5:00 a.m., when Orion is high in the south.

The Moon is at a bright waxing gibbous phase — normally a big drawback — but it will set at around 1:40 a.m. on Sunday morning; 2:45 a.m. on Monday morning . . . leaving the few hours before dawn breaks, dark for viewing.
A BLAST FROM THE PAST?

Here is why we should pay special attention to this year’s Orionids:

Last year’s Orionids were exceptional, and it is possible there may be a repeat this year. Last year, hourly rates exceeded the “normal” 25 per hour rate for five straight days . . . and between October 21 and 23, rates reached 50 to 60 per hour — more than twice the normal complement that can be expected from this display. Moreover, last years meteors were unusually bright, suggesting that the structure we passed through in 2006 was not part of the Orionid stream we normally sample.

So if you’re up …look the sky and you might just see a great show.

More meteor shower dates and times are here.

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Orionids meteor showers, Orionid, October meteors

by sduncan
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October just wouldn’t be the same without pumpkins; just try to imagine Fall without Jack-O’Lanterns, pumpkin pies, roasted pumpkin seeds, pumpkin growing contests, and even giant pumpkin regattas.

To celebrate, Farmersalmanac.com is full of fun and informative articles, recipes and video on these largest of all fruits (yes pumpkins are a fruit).

You’ll even find some pumpkin trivia, like the following:

• The word ‘pumpkin’ comes from the Greek word, ‘pepon’, which means “large melon.”
• The earliest pumpkin pie made in America was not today’s version. Pilgrims and early settlers made pumpkin pie by baling a hollowed out a pumpkin, filled with milk, honey and spices.
• Morton, Ill., home of Libby’s Pumpkin products, is popularly considered to be the “Pumpkin Capital of the World.”
• Illinois grows the most pumpkins, with residents harvesting about 12,300 acres of pumpkins annually.
• Pumpkins were believed to be a remedy for freckles and snakebites.

Of course, if I were ever bitten by a snake, I doubt I’d scream for a pumpkin (at least not initially).

Technorati Tags: pumpkins, giant pumpkin regatta. Farmers’ Almanac, Pumpkin Pie

by jdlugozima
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