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Green Peas, blue stars, and ultraviolet light

12 Apr 2013, 19:02 UTC
Green Peas, blue stars, and ultraviolet light
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The color of galaxies generally comes from its stars. That makes sense: it’s where the galaxy’s light originates, after all. Galaxies with a lot of young stars will be bluish, while galaxies dominated by older stars will shade toward red. I hedge because we’re seeing an average: by and large, galaxies aren’t going to be strongly colored.
A Green Pea galaxy. [Credit: SDSS]As a result, the Green Pea galaxies came as a surprise. These galaxies are small (hence the name) and green in color, which is all the more odd because stars are never green to our eyes. (Green Peas are not the first botanical name in astronomy. Lenticular galaxies are “lentil-shaped”, which is also why lenses are named as they are. It’s good to bean astronomer.) When astronomers see green, it’s usually due to light emitted by oxygen atoms in nebulas, but it had never been seen on such a large scale before.
Green Pea galaxies were discovered by citizen scientists working with the GalaxyZoo project. GalaxyZoo is an ongoing collaborative effort to sift through Sloan Digital Sky Survey (SDSS) and Hubble Space Telescope (HST) data to classify galaxies according to their shape and other properties. As Alice Shepherd ...

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