Blue Supergiant star shakes stellar birth theories

Apr 11, 2013
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Blue Supergiant star shakes stellar birth theories

Astronomers have tracked the formation of a blue supergiant star that, though emerging more than 55m years ago, could teach scientists today about a new mode of star formation unseen in our own galaxy. The new blue supergiant, located in galaxy IC 3418 in the constellation Virgo, was spotted using the Subaru Telescope at the National Astronomical Observatory of Japan, and was observed forming from the huge stream of cool gas stripped from the fast-moving galaxy clusters.

Although the gas-stripping process - which occurs as the Virgo cluster, among others, moves at speed through million-degree hot plasma and dark matter - had been known for some time, scientists were uncertain as to what happened to that gas once it had been shed. One theory was that IC 3418's sheddings of cool gas would vaporize amid the plasma, while another was that it would condense and form new, massive stars.

In fact, using GALEX ultraviolet imaging, the astronomy team discovered that the latter is true, a method of star creation quite dissimilar to the route to creation observed in the Milky Way. Stars in our own galaxy have sprouted in groups within cold molecular gas clouds, the Subaru Telescope team points out.

That takes place in what are described as "huge stellar nurseries", evidence of which was absent from ultraviolet observations of IC 3418:

"Intense UV-radiation usually ionizes/heats-up the surrounding gas when a star is born. Instead of any sign of heated gas, the observation showed fast winds blowing out of the stellar atmosphere at a speed of about 160 kilometers per second. Comparison with emissions from nearby stars made it clear that this massive, hot (O-type) star had passed its youth and was now aging; it was at a stage known as Blue Supergiant star and would soon face its explosive death as a supernova" NAOJ

The discovery - which is believed to be "probably the farthest star ever discovered with spectroscopic observation" according to team member Dr. Youichi Ohyama of the Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan - will demand larger telescopes, such as the Thirty Meter Telescope expected to be completed later this decade, in order to examine fully. However, it could hold the key to new understandings of star behavior.

The opposite end of that behavior has also been spotted in recent weeks. Findings by the European Space Agency's Herschel space telescope showed what would happen at the end of the life of a star similar to our own sun.


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