Two Comets Climb into Evening Sky
Two comets bright enough to see with the unaided eye will pass through the night sky in May and June 2004. One will climb high in the western evening sky in mid to late May, although it will fade as it moves higher in the sky. The other won't show up until late in the month, and will remain quite low in the southwest.
 Comet NEAT as seen in late May by the WIYN telescope in Arizona. [T. Rector et al, WIYN/NOAO/AURA/NSF]
The first comet is catalogued as C/2001 Q4 (NEAT). NEAT is the Near Earth Asteroid Tracking program, which uses automated telescopes to scan the sky for asteroids or comets that come close to Earth's orbit around the Sun. These "near-Earth objects" could potentially slam into our planet, causing major destruction.
The second comet is C/2002 T7 (LINEAR). It's one of about a hundred comets discovered by the Lincoln Near Earth Asteroid Research project, another automated asteroid and comet search program, which uses a pair of telescopes in New Mexico.
Both projects also discover many comets and asteroids that present no threat to Earth, as is the case with both NEAT and LINEAR.
Looking for the Comets
C/2001 Q4 (NEAT) will climb into view in early May. It will appear low in the west-southwest at nightfall. It should look like a modest star with a short tail extending to the upper left.
Over the next few nights, it will climb higher in the sky and move a little farther toward the north. Current predictions call for it to reach maximum brightness around May 5-10. It will pass closest to Earth on May 7, at a distance of about 30 million miles (48 million km).
Early predictions called for the comet to peak at around first magnitude, which is comparable to some of the brightest stars in the sky. But it has not brightened as much as expected, so it should put in a more modest appearance. It will not rival the brightness of Comet Hale-Bopp, which staged a spectacular show in 1996 and '97. Still, it should be visible to the unaided eye, especially in areas with relatively little "light pollution" from streetlamps and other urban light sources.
NEAT will line up with four planets on the evening of May 12. Look for brilliant Venus, the "evening star," low in the west-northwest as darkness falls. The second-brightest star-like point in the sky is Jupiter, well to the upper left of Venus. The comet will appear along the line between the two planets, a little closer to Jupiter than to Venus. (Mars and Saturn line up to the upper left of Venus.)
One other nice viewing opportunity comes on the evening of May 25, when the comet appears just to the right of the Moon. It will have faded appreciably since earlier in the month, but should still be visible in dark skies.
The comet will fade quickly after that, and drop from naked-eye visibility by early June.
C/2002 T7 (LINEAR) will peek into the evening sky in late May. Look for it beginning the last few days of May, standing well to the left of the bright star Procyon in the west. Early predictions said the comet might grow almost as bright as Procyon. Like NEAT, however, it has not performed as anticipated, so it should remain a good bit fainter than the star.
LINEAR will stand highest in the sky around June 8. Look for it just below Alphard, the star that marks the "heart" of Hydra, the water snake. The comet should be fainter than the star, with a short tail extending to the upper left. Binoculars will greatly enhance the view. LINEAR will fade quickly during June, and disappear in the glow of twilight before month's end.
Skywatchers in the southern United States should have a better view than those in the north, because the comet will stand a little higher in the sky.
Comet Background
Like all comets, NEAT and LINEAR are big balls of frozen water and gas mixed with solid particles of rock.
The comet itself is sometimes referred to as the nucleus. As it approaches the Sun, some of its ice vaporizes, which also releases tiny grains and pebbles of rock. This material forms a bright, glowing cloud around the comet, called a coma. It can span several hundred thousand miles, and makes the nucleus difficult to see and measure. (Most comets are no more than a few miles in diameter.) Finally, solar radiation and the solar wind (a steady flow of electrically charged particles from the Sun) push the gas and dust away from the comet, creating a tail that can stretch for millions of miles.
Astronomers believe that both NEAT and LINEAR are making their first trips through the inner solar system. They probably resided in the Oort Cloud, a spherical shell of comets that surround the solar system, for more than four billion years. A passing star or other disturbance nudged them from their orbits and caused them to fall toward the Sun.
Comet NEAT was discovered on August 24, 2001, and LINEAR on October 14, 2002.
-- Damond Benningfield
Resources
Gary Kronk's comet pages
History of the two comets, plus recent pictures: Comet NEAT and Comet LINEAR.
Comet Observation Home Page, Jet Propulsion Laboratory
Recent brightness reports, photographs, finder charts.
StarDate Guide to the Solar System Comets Page
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