A star-forming region in the Small Magellanic Cloud. Sometimes, the biggest stars can be found in the smallest of galactic ponds. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).
Feeling lonely this Christmas? Spare a thought for some of the most massive stars in our universe that shine so bright, but live all on their lonesome.
One would think that to build the biggest stars, you need a really big star factory, like a bubbling and churning stellar nursery stuffed full of plump baby stars gulping down as much nebulous gas a possible. However, according to a University of Michigan study, some of the biggest stars can reach a ripe, massive age in isolation.
Using the Hubble Space Telescope, the Michigan astrophysicists analyzed eight stellar monsters -- each 20 to 150 times the mass of the sun -- in the Small Magellanic Cloud (SMC). The SMC is one of the Milky Way's nearest galactic neighbors.
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Five of the massive stars had no neighboring stars and the other three lived in small clusters of ten or less stars. This finding suggests this sample of stars grew fat in a region of space with few stellar siblings.
Using one of the better analogies I've read in a press release, Joel Lamb, a doctoral student in the Department of Astronomy, likened these big stellar loners in small clusters to big fish in small ponds.
"My dad used to fish in a tiny pond on his grandma's farm," Lamb said. "One day he pulled out a giant largemouth bass. This was the biggest fish he's caught, and he's fished in a lot of big lakes. What we're looking at is analogous to this. We're asking: 'Can a small pond produce a giant fish? Does the size of the lake determine how big the fish is?'"
"Our results show that you can, in fact, form big stars in small ponds."
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Studies of massive stars are critical to our understanding of how galaxies formed and even how life was sparked. The supernovae of these massive stars produce the heavy elements we see all around us. It is these elements that formed the planets and life on Earth (as Carl Sagan famously said: "We are star stuff").
There is a heated debate as to the relationship between massive stars and the size of the cluster they live in. Surely the biggest clusters should have the biggest stars? It stands to reason that the larger cluster have more dense material to build the big stars. This new research contradicts that idea.
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The researchers are aware that the small selection of stars may not be telling the whole story. What if they are in fact orphans from other, more massive clusters?
Although two of the stars analyzed are known to come from somewhere else, the others appear to be surrounded by wispy traces of gas, leading the researchers to think those stars grew up in the neighborhood they are currently located.
This study, "The Sparsest Clusters With O Stars," appears in the Dec. 20 edition of the Astrophysical Journal (doi: 10.1088/0004-637X/725/2/1886).
Tags: Galaxies, Hubble Telescope, Stars, Stellar Physics
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