"You can think of this galaxy as a star factory run amok."
Space Telescope Science Institute
THE GALAXY NGC 1808 is in the direction of the southern constellation Columba,
about 40 million light-years away from Earth. (One light-year is 6 trillion
miles). Jim Flood, an amateur astronomer affiliated with Sperry Observatory
at Union College in New Jersey, submitted a proposal to observe the galaxy
as part of a program at the Baltimore-based Space Telescope Science Institute
to award telescope time for projects deemed deserving.
It's a unique program in that regard, said Max Mutchler, an astronomer at the institute who volunteered to help Flood execute the observing program and analyze the results. Flood, a chemist who works in technical support for a company that makes scientific instruments, was given one orbit of Hubble observing time last August, and the images were captured using Hubble's Wide Field and Planetary Camera 2. I picked something that actually had visual appeal and interest, Flood said Tuesday. What's more, the galaxy was in the southern celestial hemisphere which is generally not as well-documented as the northern hemisphere.
The new images add another piece of the puzzle in theories about star formation, Mutchler said Monday. Galaxies like our own Milky Way steadily create new stars in a process documented by Hubble images of the Orion Nebula and the Eagle Nebula. (Those images can be seen among Hubble's Greatest Hits). Those are close-up looks we can get at normal star formation, but those wouldn't be considered a starburst, Mutchler said. In contrast, the forces at work in NGC 1808 are squeezing galactic gas and dust into massive clusters composed of hundreds of thousands of stars. The star clusters show up as blue dots on the newly released images, concentrated along a line going through the center of the galaxy.
You can think of this galaxy as a star factory run amok, Mutchler said. Something triggered a relatively recent burst of star formation, and now the whole galaxy is involved in this activity. Some of the millions of stars flare up quickly and explode into supernovae. Mutchler said those supernovae eject dust that shows up as streaming filaments in high-resolution images of NGC 1808.
Why is NGC 1808 so busy in star creation? Mutchler said two moving bars of stellar material may be pushing against each other, building up the intense pressure required to create suns. The fact that you can see this perfect line of star formation is a giveaway that there is a bar somewhere, he said. Somehow that shape, that morphology is linked to star formation. You can think of it as throwing gasoline on a fire. Mutchler said the shape of the galaxy may have been altered by the gravitational pull of another galaxy passing nearby; perhaps NGC 1792. Such an interaction could have hurled gas towards the nucleus of NGC 1808, igniting the exceptionally high rate of star birth seen there, he said.
One next step might be to look at the infrared radiation given off by the galaxy, which would provide a picture less obscured by interstellar dust and gas, Mutchler said. Flood and Mutchler are continuing to analyze the results from Hubble, and Flood hopes to publish a scientific paper about his observations before August, when the data goes into the public domain. Flood notes that there is a long tradition of amateurs and professionals working together in astronomy, even though the increasing dependence on expensive observing instruments has led to more of a gap in recent years. Astronomy is one of those fields where amateurs discover comets and asteroids all the time, Flood said.