STAR BIRTH

Amateur Astronomer Studies Explosive Star Birth

by Andrea Gianopoulos

Most amateur astronomers dream of using an instrument like the Hubble Space Telescope. Analytical chemist Jim Flood of New Jersey is one of the few who has. "I felt that this was a once-in-a-lifetime opportunity to use the hottest science project going," says Flood, who selected the barred spiral galaxy NGC 1808 as a "suitable victim" for his Hubble proposal. This galaxy is roughly 40 million light-years away in the southern constellation Columba. Its large size and brightness, relatively near location, and attractive appearance all made it an ideal target. "NGC 1808 is a nice spiral spewing dramatic amounts of dust and gas from the core," says Flood.

The Hubble image shows vigorous star formation taking place at the galaxy's center. This "starburst" is probably the result of gravitational interactions with the nearby galaxy NGC 1792. Blue star clusters shine amid thick lanes of gas and dust. Hubble shows these stars are often born in compact clusters within the starburst region, and that the dense gas and dust required for star birth heavily obscures these stellar nurseries. The brightest knot of star birth is probably a giant cluster (roughly 100 light-years in diameter) at the very center of the galaxy. The other star clusters are about 10 to 50 light-years in diameter. When asked what he has learned from this experience Flood replied, "I've learned that the Hubble gathers more information than the professionals can possibly look at, and I plan to take advantage of the public domain nature of all Hubble data after a one-year period to do further research."

Flood worked with professional astronomer Max Mutchler of the Space Telescope Science Insitute. "This was the last of the 13 official Hubble amateur programs," says Mutchler, "but amateurs continue to play an important role in HST research on an informal basis." Six exposures from Hubble's Wide Field and Planetary Camera 2 (WFPC2) were combined to create the image - two in the infrared band (highlighting older stars and giving good dust penetration at wavelengths not available from Earth's surface), two in hydrogen alpha (to show hydrogen gas excited by the ultraviolet radiation of young massive O- and B-type stars in starburst regions), and two in the visual red band (to subtract the normal background stars from the hydrogen alpha exposures). Duplicate exposures were taken at each wavelength so cosmic ray hits - which look like stars - could be subtracted out of the final image.