The Comet Neat (C/2002 V1)

'Finder'

Saturday, February 2, 2003

A recently discovered comet, able to be seen shortly after darkness in the western sky, could possibly become much brighter into mid-February although the Sun will likely hinder observations due to it's glare.

Comet Neat (C/2002 V1) was discovered on November 6, 2002 and observers soon realized it was brightening quite quickly. Recent estimates report the comet to be about magnitude 5.4 and easily visible in binoculars from a relatively dark location as a small, faint fuzzy patch. Observing with a telescope at low power should reveal a slightly teardrop shape to the comet.

Astronomers who attempt to forecast the future characteristics and behavior of these cosmic vagabonds have found this one to be particularly capricious. It may not brighten much more. Or it may soon be visible to the naked eye. There has even been talk that it might shine so brightly as to be visible during broad daylight, though such high hopes have dimmed in recent days. NASA’s commonly refers the comet to as NEAT, for its discovery in November Near Earth Asteroid Tracking program at the Jet Propulsion Laboratory (JPL).

Comets brighten, and display a head and tail, because the Sun boils surface material away, which then glows with reflected sunlight. But the process in not completely understood, and each comet tends to behave a bit differently. Some even come apart as they approach the Sun. Comet NEAT has already shown itself to be an oddball, so before projecting what NEAT might do, a little history is in order.

The NEAT system, using a 1.2-meter (4-foot) telescope, is located in Hawaii and is a cooperative effort with the U.S. Air Force. A preliminary orbit for the new comet was calculated; it will make its closest approach to the Sun (called "perihelion") at a distance of 9.2 million miles (14.8 million kilometers) on Feb. 18, 2003. That's just less than one-tenth the Earth's average distance from the Sun. At the time of its discovery, the comet shone at a very feeble magnitude of +17.3 - which is about 25,000 times dimmer than the faintest stars that can be perceived with the unaided eye. Astronomers use positive numbers for dim objects. The faintest star visible shines at about magnitude 6.5, but can only be seen under absolutely dark sky conditions away from all local lighting. The brightest objects achieve zero or negative magnitudes. The first predictions indicated that the comet would dutifully brighten as it approached the Sun, possibly reaching second magnitude (the brightness of Polaris, the North Star) at perihelion. At that time however, the comet would be positioned just six degrees from the Sun in our sky and would be hopelessly drowned-out by the brilliant solar glare.

But during December, a curious thing began to happen. Erratic behavior Comet NEAT started brightening very rapidly late last year, far outpacing even the most optimistic brightness forecasts. Were it to continue brightening in the same manner as it approached the Sun, the comet would have likely evolved into an amazingly brilliant object, perhaps briefly becoming visible even in broad daylight, a feat commonly achieved only by the Sun, the Moon and the planet Venus (for experienced sky watchers) But by early January the level of brightening slowed considerably.

Suggestions were then put forward that comet NEAT might actually start to fizzle out as it crossed the Earth's orbit on its inbound approach to the Sun; perhaps its brightening would stop completely, or it might even start getting dimmer. Were it just a small comet, NEAT would certainly become well cooked at its close approach to the Sun and, in addition, might be subjected to great disruptive forces that could break it up or even destroy it totally. But in mid January, a new orbit calculated for NEAT demonstrated that it is moving around the Sun in a highly elliptical orbit, taking roughly 37,000 years to make one complete revolution around the Sun. That means the comet likely has been through the inner solar system at least once before - probably more than once - suggesting that it has survived previous close brushes with the Sun.

Currently, comet NEAT is shining at around magnitude +5.5 and might actually be glimpsed by sharp-eyed observers in a dark, clear sky amidst the faint stars of the constellation Pisces For several days it will be located below and to the right of a ring-like pattern of dim stars known as the Western Fish or "Circlet" of Pisces. In the early evening sky it can be readily picked up in binoculars about an hour or so after sunset as a small, circular patch of light with an almost star-like center. In small telescopes the comet's gaseous head or "coma" appears to fill a region of the sky roughly one-fifth of the Moon's apparent diameter as seen from Earth (an actual linear distance of 148,000 miles, or 237,000 ). The comet also displays a short, faint, two-pronged tail composed chiefly of ionised gases.

Comet Neat can be found just beside Eridanus. The chart above shows the positions now , April. 13, as seen at 0:00 UT. The direction of the comet's tail is shown, though it is not yet possible to say how bright the comet will be or whether the tail will be visible to the naked eye.

At the start of February the comet is still 20 degrees up from the western horizon after evening twilight and there is no moonlight interference. The highly evolved complex gas tail will make it an excellent target for astrophotography.

The comet might brighten to magnitude +3 or +4 as it drops lower into the evening twilight and might be lost to view sometime around Feb. 10. Predicting the brightness at the February 18 perihelion is really guesswork, but most likely it will be somewhere between magnitude +1 and -2

Even is the comet does not brighten dramatically, anyone with an Internet connection will have a chance to watch it as it rounds the Sun, courtesy of the LASCO C3 coronagraph mounted on the SOHO spacecraft. SOHO is a cooperative mission between the European Space Agency and NASA. The spacecraft is stationed in a halo orbit around the Sun-Earth L1 Lagrangian point, a position roughly 930,000 miles (1,500,000 kilometres) sunward of Earth. At this point in space, the orbital period of SOHO exactly matches the orbital period of Earth. From this orbit, SOHO is able to observe the Sun 24 hours a day. Many people used the SOHO web pages to watch another recent comet, called Kudo-Fujikawa (C/2002 X5). It first appeared on SOHO snapshots Jan. 25, looking like a small, white teardrop directly above the Sun, at the top of the circular frame. During the following days, the comet made its way diagonally down to one side of the Sun (which is behind an occulting disk at the center of the field). Comet Kudo-Fujikawa remained within the field of view of SOHO through Jan. 31. Comet NEAT's turn to come within SOHO's camera range will be between Feb. 16 and Feb. 20, allowing ground-based viewers to safely monitor it on their home computers even though it will be very near to the blindingly bright disk of the Sun.

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