Smith's Cloud

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Smith's Cloud is a high velocity cloud of hydrogen gas with a mass of approximately one million MSun measuring 11,000 light years long by 2,300 light years wide.[1] The cloud is between 9,800 parsecs (32,000 ly) and 15,100 pc (49,000 ly) from Earth[2] and has an angular diameter of 10 to 12 degrees, approximately as wide as Orion, or about 20 times the diameter of the full moon, although the cloud is not visible to the naked eye.[3] Smith's Cloud is in the constellation Aquila at galactic coordinates right ascension (l)=40, declination (b)=-1.

In January 2008 it was announced the cloud's apparent direction is towards the disc of the Milky Way at 240 kilometres per second. Smith's Cloud is expected to merge with the Milky Way in 20 to 40 million years at a point in the Perseus arm, one quarter away around the galaxy from Earth's position. Astronomers believe it will strike the Milky Way disk at a 45-degree angle, and its impact is expected to produce a burst of star formations.[3] Smith's Cloud is named after its discoverer in 1963, Gail Bieger, née Smith, who was an astronomy student at Leiden University in the Netherlands.[3]

[edit] References

  1. ^ Heroux, AJ (December 2006). "Smith’s Cloud (HVC) in 21 cm HI emission" (abstract). Bulletin of the American Astronomical Society 38: 1149. American Astronomical Society. Bibcode: 2006AAS...20917213H. 
  2. ^ Wakker, B. P. (2008). "Distances to Galactic High‐Velocity Clouds. I. Cohen Stream, Complex GCP, Cloud g1". The Astrophysical Journal 672: 298. doi:10.1086/523845. 
  3. ^ a b c Lockman, Felix J. (2008). "The Smith Cloud: A High-Velocity Cloud Colliding with the Milky Way". The Astrophysical Journal 679: L21. doi:10.1086/588838. 
    See also David Shiga. "Giant gas cloud to crash into our galaxy", NewScientist, 11 January 2008. Retrieved on 2008-02-07. 

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