To star hunter Goran Sandell, finding a new star is like a first date: nice to get the attention, but you never know if it will amount to much.
Having found several stars and protostars before, the senior scientist with the Universities Space Research Association finally found a whopper: a protostar 300 times more massive than our Sun and 300 times bigger than our Solar System. Sandell hopes it will help scientists understand protostars -- clouds of gas and dust that develop later into stars -- and how they mature.
"Everything we think we understand about stars forming is from low-mass stars", Sandell said
Sitting a mere 7,000 light years away and burning at a million degrees Centigrade, this star nursery previously was shrouded by a curtain of roiling dust. Smaller stars don't have as much surrounding them, so they are easier to see, but Sandell used a new camera that detects the minute radiation that comes from the cosmic dust and gases that make stars.
The protostar, affectionately named NGC 7358 S in part because it is a bright nebulous object in a dark region of the sky, looks like a small, disk-shaped gas cloud embedded in an enormous filamentary gas formation. It is so dense that Sandell wagers gravitational collapse has already begun. The disks show no evidence of breaking into smaller stars, but the final star will be less than 300 solar masses because star formation is an inefficient process.
Sandell presented his work earlier this month at the American Astronomical Society meetings in Pasadena, California.
Not just a fish story
Stars form when a cosmic dust cloud becomes unstable and starts to collapse, with gravity pulling material into the center.
"Basically, the star grows with the spread of free-fall," Sandell says. "More and more gas falls into it, so that the temperature increases, and then sooner or later it reaches a million degrees in the center, starting nuclear fusion. Fusion puts another force onto it and actually pushes out, which now relaxes pressure and stops the in-falling gas."
With larger stars, says Sandell, this process is sped up because there's a bigger gravitational pull. The process may take 10,000 years for a high-mass star, while smaller stars may take a million years to develop which also makes large protostars harder to find.
So finding NGC 7358 S was like hooking a big fish.
Cool telescope
The camera used to find this protostar is the Submillimeter Common User Bolometer Array, or SCUBA. SCUBA uses detectors cooled to a tenth of a degree above absolute zero (-273 degrees Celsius) to measure the radiation emitted from the cosmic dust particles as they fall. The submillimeter wavelengths are longer than infrared, but shorter than radio waves.
SCUBA was mounted on the 15-meter James Clerk Maxwell Telescope (JCMT). Built in 1987, JCMT is the largest telescope of its class in the world and sits 2.5 miles (4.1 km) above sea level on the top of Mauna Kea, a mountain on the big island of Hawaii.
Sandell describes the JCMT as, "one of the best Submillimeter Common User Bolometer Array sites in the Northern Hemisphere," because it encounters no light pollution and sits at an altitude where it is above 97 percent of the air's water vapor, the biggest obstacle to visualizing sub-millimeter wavelengths.
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