Except this fuzzy blob wasn't a galaxy, it was a comet -- complete with a star-like nucleus, a hazy coma, and a diffuse tail. At the time, the comet was about five times farther from the Sun than Earth, or roughly as far out as Jupiter (although the comet was not near the planet).
Dalcanton reported her find to the Central Bureau for Astronomical Telegrams, the world clearing-house for such discoveries. Working from the comet's reported position, Gareth Williams of the Central Bureau quickly linked the comet to other observations of it made by teams searching for asteroids. These detected the comet but reported it merely as an asteroid.
Because Dalcanton recognized what it really was, the new object was named for her, becoming Comet Dalcanton (C/1999 F2).
The Sloan Digital Sky Survey is working to map the locations and redshifts for more than a million galaxies and some 100,000 quasars across half the northern sky. The survey will explore a volume of space a hundred times greater than any previous survey. The project uses a 2.5-meter (98-inch) telescope located atop Apache Peak in New Mexico's Sacramento Mountains.
The telescope spends part of the time taking photos to locate galaxies. Then as candidate galaxies are identified, the telescope makes spectrograms of them to determine their redshifts. Redshift is a change in the color of light produced by the expanding universe; objects farther away have greater redshifts.
When the galaxies' distances are combined with their positions, astronomers can see how galaxies sprawl through the universe in three dimensions. This is a key part of learning how galaxies and the universe itself formed and evolved.
Among the survey's other findings is a puzzling new kind of object, rich in methane, that is smaller than a star but bigger than Jupiter. The survey also holds the record for the quasar with the greatest redshift and farthest distance.
The discovery of Comet Dalcanton was lucky in second way because the comet is an unusual one. At discovery, the comet was still 10,000 times fainter than the naked eye could detect but its tail showed that it was much more active than most comets at a similar distance from the Sun. Its high activity leads comet scientists to suspect it may be a first-time visitor from the Oort Cloud -- the hypothesized shell of comets that surrounds the Sun at a distance of one to two light-years.
Unfortunately, Comet Dalcanton was closest to the Sun in August 1998 and is on its way back out. It won't be returning for another 186,000 years.
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