Posted: 01 Nov 2010 08:03 AM PDT

November 1st, 2010 - Astronomy Essentials

Meteor experts at NASA have determined that – although it's a long shot – the evenings of November 2 and 3 might feature a meteor shower from Comet Hartley 2, the comet photographed and glimpsed by many with ordinary binoculars over this past month. These experts have jokingly dubbed this possible meteor shower the "Hartley-ids, " in the comet's honor.

When any comet – such as Comet Hartley 2 – nears the sun, its ices loosen and the comet sheds a trail of debris. If the Earth passes through a cloud of comet dust left behind by Hartley 2, bits and pieces from the comet will burn up in Earth's upper atmosphere as "Hartley-id" meteors.

The story of how this possible meteor shower came to be suggested by experts is fascinating, and you can read it here.

We emphasize that a meteor shower from this comet might or might not materialize. As always with any meteor shower, you'll have to wait and watch, preferably under a dark country sky. On November 2 and 3 – at nightfall and into the evening – sprawl out on a reclining lawn chair and look upward. If the meteors do materialize, they are likely to be slow-moving. Tracing the paths of the "Hartley-id" meteors backward, they will appear to come from the constellation Cygnus the Swan.

Of course, you don't have to know where this constellation lies to be on the lookout for this possible meteor shower. If the shower materializes, the meteors will fly in various directions and in front of any number of constellations. Cygnus simply marks the radiant point, or point of origin, of these meteors.

Your first chance to see Comet Hartley 2 itself in a dark sky will probably be in late October. In late October and early November, Comet Hartley 2 will pass in front of the feet of the constellation Gemini, to the right of Gemini's brightest stars, Castor and Pollux. You'll have more moon-free viewing time in November, but keep in mind that the already faint comet will probably be dimming by the day, as it leaves the inner solar system.

After midnight and before dawn on November 4, 5 and 6, Comet Hartley will be in the vicinity of Procyon, the brightest star in the constellation Canis Minor. The best time to look is during the wee hours before dawn, because that's when Procyon and the comet climb highest in the sky.

Looking for a detailed sky chart showing Comet Hartley 2? Click here.

The EPOXI spacecraft is scheduled to make its close encounter with Comet Hartley 2 on November 4. Scroll down to read more under the subheading Deep Impact spaceraft also headed from Comet Hartley 2. Or click here.

Want to see planets, meteor showers, eclipses? Visit our night sky page – updated daily!

What does the comet look like?

People have been reporting seeing Comet Hartley 2 in October 2010 skies – with binoculars – with some light pollution. A few claim to have spotted it with the unaided eye as the faintest of blurs, but only in areas of pristine darkness. This comet remains a challenge, even with binoculars. The image at right shows Comet Hartley 2 photographed on September 29, 2010. The photographer – Alan Murta – said he didn't manage to see it with binoculars from his (somewhat light-polluted) location on the outskirts of a city. This is just a long-exposure camera shot, he said – no telescope used. See the comet? It's in the middle of this photo: the fuzzy object just above and to the right of the star in the photo's center. That star is Lambda Cassiopeiae, by the way.

Comet Hartley 2 has been reported as being large and diffuse, meaning its light is spread out over a wide area. The best conditions for seeing it are still to be found under a dark, country sky – free of city lights and moon. When searching for the comet, try using averted vision. That's the technique of looking to one side of the faint object you seek on the sky's dome, instead of directly at it.

Comets are surprising objects in many ways. They are mysterious visitors – loosely bound balls of ices – from the outer solar system. Sometimes, comets appear without warning. Comet Hartley 2 has been expected for many years, however. Officially designated 103P/Hartley, it is a periodic comet, which returns again and again near our sun and Earth. Its orbital period is thought to be 6.46 years.

Even so, the brightness and appearance of this comet – or any comet – never follows an ironclad forecast. Don't be surprised if Comet Hartley 2 exceeds or falls shy of expectation.

You will need a dark sky – free of city lights or moonlight – to see this comet. Through your binoculars, it looks like a smudge of light against the dark sky background. Comet Hartley appears as a faint, fuzzy patch of light.

The element of suspense always accompanies the return of a comet to Earth's sky. That's one reason they are fun to see!

Deep Impact spacecraft also headed to Comet Hartley 2. By the way, the Deep Impact spacecraft – which was launched by NASA in 2005 and successfully sent a collider into Comet 9P/Tempel – had its orbit around the sun tweaked in May of 2010 with the goal of sending it close to Comet Hartley 2. This mission has now been re-designated EPOXI. The craft will pass most closely to the comet in early November, 2010. Mission overseers are provided status updates for EPOXI's impending sweep past Hartley 2.

All in all, it will be an interesting autumn season for comets, thanks to Comet Hartley 2. Be sure to make friends with the bright stars Castor and Pollux and its constellation Gemini, for the comet will be passing through this constellation in late October. The trick to comet hunting is to know right where to look and right when to look. Our next moon-free view of the comet will come in late October, and the comet should probably be visible with an optical aid from then through early November. Most people report the comet as being faint. It will be interesting to see how much longer we'll be able to view Comet Hartley 2, our transitory visitor to Earth's starry sky.

And don't forget – find a dark, open sky and watch for the "Hartley-id" meteors on the evenings of November 2 and 3!

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Moonlight Meteor Shower Spawned By Halley's Comet - msnbc.com

Posted: 20 Oct 2010 07:20 AM PDT

A junior version of the famous Perseid meteor shower thought to have originated from the remains of Halley's Comet will hit its peak over the next week, but the light of the moon may intrude on the sky show.

This upcoming meteor display is known as the Orionids because the meteors seem to fan out from a region to the north of the Orion constellation's second brightest star, ruddy Betelgeuse.

The annual event peaks before sunrise on Thursday (Oct. 21) but several viewing opportunities arise before then for skywatchers in North America. [ Where to look to see the Orionids ]

The shooting stars are created by small bits of space dust — most no larger than sand grains — thought to be left over from the famed Halley's Comet, which orbits the sun once every 76 years.

Currently, Orion appears ahead of us in our journey around the sun, and has not completely risen above the eastern horizon until after 11 p.m. local daylight time.

The constellation is at its best several hours later. At around 5 a.m. – Orion will be highest in the sky toward the south – Orionids typically produce around 20 to 30 meteors per hour under a clear, dark sky.

But skywatchers beware: You will be facing a major obstacle in your attempt to observe this year's Orionid performance. As bad luck would have it, the moon will turn full on Oct. 23. Bright moonlight outshines fainter meteors, seriously reducing the number anyone can see.

The gradual build up to the full moon will hamper – if not outright prevent – dark-sky observing during the Orionid meteor shower's peak on Oct. 21.

The Orionids are actually already underway, having been active only in a very weak and scattered form since about Oct. 2. But a noticeable upswing in activity is expected to begin around Oct. 17, leading up to their peak night.

"Orionid meteors are normally dim and not well seen from urban locations," notes meteor expert, Robert Lunsford, adding that "it is highly suggested that you find a safe rural location to see the best Orionid activity."

Damage control for 2010

With all this as a background, perhaps the best times to look this year will be during the predawn hours several mornings before the night of full moon. That's when the constellation Orion (from where the meteors get their name) will stand high in the northeast sky.

In fact, three "windows" of dark skies will be available between moonset and the first light of dawn on the mornings of Oct. 18, 19 and 20.

Generally speaking, there will be about 150 minutes of completely dark skies available on the morning of the 18th.This shrinks to about 100 minutes on the 19th, and to about 50 minutes by the morning of the 20th.

This skywatching table shows prime Orionid meteor shower viewing times for some select U.S. cities.

In the table, all times are a.m. and are local daylight times. "Dawn" is the time when morning (astronomical) twilight begins. A "Window" is the number of minutes between the time of moonset and the start of twilight.

For example: When will the sky be dark and moonless for Orionid viewing on the morning of Oct. 20 from Houston?

Answer: There will be a 50-minute period of dark skies beginning at moonset (5:16 a.m.) and continuing until dawn breaks (6:06 a.m.).

Perhaps up to a dozen forerunners of the main Orionid display might appear to steak by within an hour's watch on these mornings, particularly on the 20th, the morning before the peak. It might even be worthwhile to try on Thursday morning, Oct. 21, although for most places, the moon will not set until just after the first light of dawn.

Halley's legacy

In studying the orbits of many meteor swarms, astronomers have found that they correspond closely to the orbits of known comets.

The Orionids are thought to result from the orbit of Halley's Comet, as some of the dust that has been shed by this famous object intersect earth's orbit around the sun during October.

There are actually two points along Halley's path, where it comes relatively near to our orbit. Another one of these points occurs in early May causing a meteor display from the constellation Aquarius, the Water Carrier.

The tiny particles that are responsible for the Orionid and Aquarid meteors are – like Halley itself – moving through space in a direction opposite to that the earth. This results in meteors that ram through our atmosphere very swiftly at 41 miles (66 km) per second. Of all the meteor displays, only the November Leonids move faster.

Orionid postmortem

After the peak, activity will begin to slowly descend, although most of the meteors will be squelched by the light of the moon. Rates drop back to around five per hour around Oct. 26. The last stragglers usually appear sometime around Nov. 7.

It is indeed unfortunate that the Moon will likely obliterate most of the Orionids in the nights following the peak, but the viewing odds will be much better before the break of dawn on those mornings leading up to the peak. Almost certainly, you should sight at least a few of these offspring of Halley's Comet as they streak across the sky.

In the absence of moonlight a single observer might see at least a couple of dozen meteors per hour on the morning of the peak, a number that sadly can not be hoped to be approached in 2010. In fact, it appears that this year, fans of the Orionids will be uttering the same lament that the old Dodger fans in Brooklyn used to: "Wait till next year!"

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Space Pickle? Bowling Pin? Comet Hartley 2 Takes Curious Shape - msnbc.com

Posted: 30 Oct 2010 06:11 AM PDT

When a NASA probe takes a close look at Comet Hartley 2 next week, it will find the icy wanderer to be curiously pickle-shaped, new radar images reveal.

Comet Hartley 2 will be visited by NASA's Deep Impact spacecraft on Nov. 4 in a close flyby. To prepare for the event, astronomers used the Arecibo Observatory in Puerto Rico to take new radar observations that revealed the comet's pickle shape. [ Photo of the pickle-shaped Comet Hartley 2.]

The series of radar images was taken between Oct. 25 and Oct. 27. The images show Comet Hartley 2 as an elongated cylindrical object.

"It kind of looks like a cross between a bowling pin and a pickle," said Tim Larson, project manager of the Deep Impact probe's comet rendezvous mission at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Only it's about 14,000 times larger and hurtling through space at 23 miles per second."

Scientists using Arecibo's massive radar dish began observations of Comet Hartley 2 on Oct. 24, just four days after the comet zoomed to within 11 million miles (17.7 million km) of Earth its closest approach to our planet since the comet's discovery in 1986. Arecibo's observations are scheduled to continue through today (Oct. 29), researchers said.

On Nov. 4, the Deep Impact spacecraft will fly to within 435 miles (700 km) of the comet as part of a NASA mission called EPOXI.

"Observing Comet Hartley 2 from the Earth with radar was like imaging a 6-inch spinning cucumber from 836 miles away," said Jon Giorgini, a scientist at JPL and a member of the Arecibo team that imaged the comet.

The observations are helping scientists characterize Comet Hartley 2 ahead of Deep Impact's close encounter, Giorgini said. For example, researchers now know that the comet's nucleus is highly elongated and about 1.4 miles (2.2 km) long, and that it rotates around itself about once every 18 hours.

"In addition, we now know the size, speed and direction of particles being blown off the comet, and we immediately forwarded all this information to the EPOXI team," Giorgini said.

Just what a celestial pickle means for the EPOXI mission remains to be seen, researchers said. Mission scientists are discussing the new findings and what if anything they signify for the upcoming comet encounter.

Comet Hartley 2 completes its long, looping sojourn around the sun every 6.5 years. It is a very active comet, researchers said, spitting lots of dust and vapor when it nears the sun and warms up which is happening now.

Deep Impact's close flyby should help scientists learn more about comet structure and evolution, as well as the early days of the solar system, researchers have said.

This is the Deep Impact spacecraft's second comet encounter. The spacecraft served as the mothership for NASA's Deep Impact mission, which intentionally crashed a probe into Comet Tempel 1 in 2005 to study the object's composition.

Now, the Deep Impact spacecraft is being put to other uses it's tracking and studying various celestial objects under the umbrella of NASA's broad EPOXI mission. The name is derived from the mission's dual science investigations the Extrasolar Planet Observation and Characterization (EPOCh) and Deep Impact Extended Investigations (DIXI).

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Meteor

Wednesday, November 3, 2010

“Comet Hartley 2 to bring meteor shower on November 2 and 3? - Earth & Sky” plus 2 more

“Comet Hartley 2 to bring meteor shower on November 2 and 3? - Earth & Sky” plus 2 more

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