The Orion Nebula is a nearby cloud of gas and dust.
Mystery "masers" in the Orion Nebula
29 Jun 2009
The Orion Nebula is one of the most famous sights in the night sky. Visible to the naked eye as a faint smudge (from a dark viewing location), through a telescope it is revealed as a huge, stunningly beautiful cloud of gas and dust hanging in space.
It also contains several clusters of hot young stars. In fact, the nebula's bright glow comes from gas and dust that are illuminated by the intense ultraviolet radiation from these stars.
The nebula is about 1,300 light-years away, making it the closest "nursery" of massive stars and one of the best-studied such regions in the sky.
But despite its fame, brightness and proximity, astronomers still do not understand it very well.
It contains dramatic outflows of gas, for example, which could be driven by a single star or perhaps by a cluster of stars—astronomers aren't quite sure.
The reason for their ignorance is in part because the nebula is so crowded with stars, and in part because its dust clouds obscure many regions from view at normal optical wavelengths.
The brightest object in the nebula shines with as much light as 100,000 suns, but in the last decade astronomers worked out that this source was itself comprised of several smaller ones.
< A false-colour image of the central region of the Orion Nebula combining data from the Hubble Space Telescope and the Chandra X-ray Observatory.
It turns out that one of these smaller objects, called "Source I," is the dominant young star in the region, and an enigmatic one at that. Its motions suggest that it was ejected from another star system just a few hundred years ago.
Other evidence hinted that it is surrounded by regions of gas that produce natural radio wavelength emissions, known as masers. Masers are the radio equivalents of lasers, and typically indicate dense gas clouds around young stars.
Centre for Astrophysics (CfA) astronomers Ciriaco Goddi, Lincoln Greenhill, Liz Humphries, and Lynn Matthews, together with two colleagues, have used high resolution radio images to build up a map of the region around Source I. By studying several types of gas in the region they have been able to confirm for the first time that maser emissions are indeed present.
Moreover, they can attribute the star's outflow to a complex two-lobed structure, and trace it to its origin in a region very close to Source I roughly comparable in size to that of our Solar System, which is very small by astronomical standards.
Some computer modelling remains to be completed, but the results so far go a long way towards figuring out what is going on in at least this region of the Orion Nebula, and offering clues about similar activity elsewhere in young star clusters.
Adapted from information issued by CfA / NASA / CXC / Penn State / E.Feigelson & K.Getman et al. / ESA / STScI / M. Robberto et al.
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