Comet Lulin visits inner Solar System 26FEB09

http://astronomynow.com/090223CometLulinvisitsinnerSolarSystem.html

Comet Lulin visits inner Solar System
BY DR EMILY BALDWIN
ASTRONOMY NOW
23 February, 2009

On 24 February Comet Lulin will make its first visit to the inner Solar System, streaking past the Earth at a distance of 38 million miles, or 160 times further than the Moon. Comet Lulin, formally known as C/2007 N3, was discovered last year byastronomers at Taiwan's Lulin Observatory. Nicknamed the "green comet", Lulin's atmosphere contains poisonous cyanogen and diatomic carbongases. Researchers at the University of Leicester will be using NASA's Swift satellite to monitor the comet in X-ray, ultraviolet and optical light as it closes in on the Earth this week.
"The wonderful ease of scheduling of Swift and its joint UV and X-raycapability make Swift the observatory of choice for observations like these," says Dr Julian Osborne, leader of the Swift project at Leicester. The University of Leicester played a major role in developing Swift's X-Ray Telescope.

[Image]

This image of Comet Lulin taken 28 Jan merges data acquired by Swift's Ultraviolet/Optical Telescope (blue and green) and X-Ray Telescope (red). At the time of the observation, the comet was 99.5 million milesfrom Earth and 115.3 million miles from the Sun. Image: Univ. of Leicester/NASA/Swift/Carter et al. Comets are thought to represent some of the most pristine ingredients ofthe Solar System. They are made up of dust, gas and ice, and as they approach the Sun, the frozen components sublime and stream out in tails. Swift observations of the comet on 28 January revealed that it is certainly active. "The UVOT data show that Lulin was shedding nearly 800 gallons of water each second," says team member Dennis Bodewits, a NASA Postdoctoral Fellow at the Goddard Space Flight Center in Greenbelt,which is enough to fill an Olympic-size swimming pool in less than 15 minutes. Although Swift can't see water directly, ultraviolet light from the Sunquickly breaks apart water molecules into hydrogen atoms and hydroxyl (OH) molecules, the latter of which Swift's Ultraviolet/OpticalTelescopes (UVOT) can detect. "This gives us a unique view into the types and quantities of gas a comet produces," Bodewits explains. The images taken so far reveal a hydroxyl cloud spanning a distance greater than the distance between Earth and the Moon, and a tail streaming off at an angle. Solar radiation pushes the icy grains awayfrom the comet, and as they gradually evaporate, they create a thin tail of hydroxyl molecules. Farther from the comet, even the hydroxyl molecule succumbs to solar ultraviolet radiation, breaking into its constituent oxygen and hydrogen atoms."The solar wind - a fast-moving stream of particles from the Sun -interacts with the comet's broader cloud of atoms," says Stefan Immler, also at Goddard. "This causes the solar wind to light up with X-rays,and that's what Swift's XRT sees." This interaction, called charge exchange, results in X-rays from most comets when they pass within about three times Earth's distance from the Sun. Because Lulin is so active and is losing a lot of gas, its X-ray emitting region extends in a largecloud far sunward of the comet. The team hope that the forthcoming observations of Lulin will reveal more on the comet's chemistry andenable scientists to build up a three-dimensional picture of the cometduring its maiden voyage through the Solar System.Comet Lulin will be visible to the naked eye, and for most locations inthe Northern Hemisphere will be easiest to spot after midnight when itis high in the sky. In small telescopes it will appear as a dim fuzzy"star" - brighter in the centre and more diffuse around the edges. It will fade from view by mid-March.

COMET LULIN & SATELLITE DEBRIS UPDATES

Space Weather News for Feb. 18, 2009http://spaceweather.com

COMET LULIN UPDATE: Comet Lulin is approaching Earth and brightening rapidly. Observers say it is now visible to the naked eye as a faint (magnitude +5.6) gassy patch in the constellation Virgo before dawn. Even city dwellers have seen it. Backyard telescopes reveal a vivid green comet in obvious motion. Just yesterday, amateur astronomers watched as a solar wind gust tore away part of the comet's tail, the second time this month such a thing has happened. Lulin's closest approach to Earth (38 million miles) is on Feb. 24th; at that time the comet could be two or three times brighter than it is now.
Browse the gallery for the latest images: http://spaceweather.com/comets/gallery_lulin_page8.htm

SATELLITE DEBRIS: More than a week has passed since the Feb. 10th collision of Iridium 33 and Kosmos 2251 over northern Siberia, and the orbits of some of the largest fragments have now been measured by US Strategic Command. Today's edition of http://Spaceweather.com features global maps showing where the debris is located. Only 26 fragments are currently plotted, but that number will grow as radar tracking of the debris continues. Check back often for updates.

Comet Lulin (C/2007 N3) Loses Part of Its Tail

Photo credit: Ernesto Guido, Giovanni Sostero & Paul Camilleri [more]

Space Weather News for Feb. 5, 2009
http://spaceweather.com/

COMET TAIL: Comet Lulin (C/2007 N3) is approaching Earth and putting on a good show for amateur astronomers. Yesterday, Feb. 4th, observers witnessed a "disconnection event." A gust of solar wind tore off part of the comet's tail in plain view of backyard telescopes. Photos of the event are featured on today's edition of http://spaceweather.com/.
Activity in the comet's tail and atmosphere will become even easier to see in the weeks ahead as Lulin nears closest approach on Feb. 24th. At that time the comet will lie only 38 million miles from Earth and it should be visible to the naked eye. In the meantime, please note that Feb. 5th-7th, is an especially good time to find Comet Lulin in the pre-dawn sky. The comet is gliding beautifully close to the naked-eye double star Zubenelgenubi. Just point your binoculars at the double star and the comet will materialize right beside it.
Visit http://spaceweather.com/ for photos, sky maps and more information.

Comet Lulin-Green Comet Approaches Earth 4FEB09

Photo by Jack Newton 2009 (c)

http://science.nasa.gov/headlines/y2009/04feb_greencomet.htm
Green Comet Approaches Earth
NASA Science news02.04.2009 February 4, 2009:

In 1996, a 7-year-old boy in China bent over the eyepiece of a small telescope and saw something that would change his life--a comet of flamboyant beauty, bright and puffy with an activetail. At first he thought he himself had discovered it, but no, helearned, two men named "Hale" and "Bopp" had beat him to it. Mastering his disappointment, young Quanzhi Ye resolved to find his own comet one day.And one day, he did. Fast forward to a summer afternoon in July 2007. Ye, now 19 years old and a student of meteorology at China's Sun Yat-sen University, bent over his desk to stare at a black-and-white star field. The photo was taken nights before by Taiwanese astronomer Chi Sheng Lin on "skypatrol" at the Lulin Observatory. Ye's finger moved from point to point--and stopped. One of the stars was not a star, it was a comet, and this time Ye saw it first.Comet Lulin, named after the observatory in Taiwan where the discovery-photo was taken, is now approaching Earth. "It is a green beauty that could become visible to the naked eye any day now," says Ye. Amateur astronomer Jack Newton sends this photo from his backyard observatory in Arizona: http://science.nasa.gov/headlines/y2009/images/greencomet/Jack-Newton1.jpg

"My retired eyes still cannot see the brightening comet," says Newton,"but my 14-inch telescope picked it up quite nicely on Feb. 1st."The comet makes its closest approach to Earth (0.41 AU) on Feb. 24,2009. Current estimates peg the maximum brightness at 4th or 5th magnitude, which means dark country skies would be required to see it.No one can say for sure, however, because this appears to be Lulin's first visit to the inner solar system and its first exposure to intense sunlight. Surprises are possible.Lulin's green color comes from the gases that make up its Jupiter-sized atmosphere. Jets spewing from the comet's nucleus contain cyanogen (CN:a poisonous gas found in many comets) and diatomic carbon (C2). Both substances glow green when illuminated by sunlight in the near-vacuum ofspace.In 1910, many people panicked when astronomers revealed Earth would passthrough the cyanogen-rich tail of Comet Halley. False alarm: The wispy tail of the comet couldn't penetrate Earth's dense atmosphere; even it if had penetrated, there wasn't enough cyanogen to cause real trouble. Comet Lulin will cause even less trouble than Halley did. At closest approach in late February, Lulin will stop 38 million miles short of Earth, utterly harmless.To see Comet Lulin with your own eyes, set your alarm for 3 am. The comet rises a few hours before the sun and may be found about 1/3rd of the way up the southern sky before dawn. Here are some dates when it is especially easy to find:
sky map

Feb. 6th:
Comet Lulin glides by Zubenelgenubi, a double star at the fulcrum of Libra's scales. Zubenelgenubi is not only fun to say (zuBEN-el-JA-newbee), but also a handy guide. You can see Zubenelgenubi with your unaided eye (it is about as bright as stars in the Big Dipper); binoculars pointed at the binary star reveal Comet Lulin in beautiful proximity.
[sky map]

Feb. 16th:
Comet Lulin passes Spica in the constellation Virgo. Spica is a star of first magnitude and a guidepost even city astronomers cannotmiss. A finderscope pointed at Spica will capture Comet Lulin in the field of view, centering the optics within a nudge of both objects. [skymap ]

Feb. 24th:
Closest approach! On this special morning, Lulin will lie just a few degrees from Saturn in the constellation Leo. Saturn is obvious to the unaided eye, and Lulin could be as well. If this doesn't draw you out of bed, nothing will.
[sky map]

Ye notes that Comet Lulin is remarkable not only for its rare beauty,but also for its rare manner of discovery. "This is a 'comet ofcollaboration' between Taiwanese and Chinese astronomers," he says. "The discovery could not have been made without a contribution from both sides of the Strait that separates our countries. Chi Sheng Lin andother members of the Lulin Observatory staff enabled me to get the images I wanted, while I analyzed the data and found the comet."Somewhere this month, Ye imagines, another youngster will bend over an eyepiece, see Comet Lulin, and feel the same thrill he did gazing at Comet Hale-Bopp in 1996. And who knows where that might lead...?"I hope that my experience might inspire other young people to pursue the same starry dreams as myself," says Ye.