Local Bubble
The Local Bubble is a cavity in the interstellar medium (ISM) of the Orion Arm of the Milky Way. It is at least 300 light years across and has a neutral hydrogen density of about 0.05 atoms per cubic centimetre, or approximately one tenth of the average for the ISM in the Milky Way (0.5 atoms/cc), and half that for the "Local Fluff", or Local Interstellar Cloud (0.1 atoms/cc). The hot diffuse gas in the Local Bubble emits X-rays.
The very sparse, hot gas of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years.[1] It was once thought that the most likely candidate for the remains of this supernova was Geminga ("Gemini gamma-ray source"), a pulsar in the constellation Gemini. More recently, however, it has been suggested that multiple supernovae in subgroup B1 of the Pleiades moving group were more likely responsible.[2]
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[edit] Description
The Solar System has been traveling through the region currently occupied by the Local Bubble for the last five to ten million years.[1] Its current location lies in the Local Interstellar Cloud, a minor region of denser material within the Bubble. The cloud formed where the Local Bubble and the Loop I Bubble met. The gas within the LIC has a density of approximately 0.1 atoms per cubic centimeter.
The Local Bubble is not spherical, but seems to be narrower in the galactic plane, becoming somewhat egg-shaped or elliptical, and may widen above and below the galactic plane, becoming shaped like an hourglass. It abuts other bubbles of less dense interstellar medium (ISM), including, in particular, the Loop I Bubble. The Loop I Bubble was created by supernovae and stellar winds in the Scorpius-Centaurus Association, some 500 light years from the Sun. The Loop I Bubble contains the star Antares (also known as Alpha Scorpii), as shown on the diagram above right. Other bubbles which are adjacent to the Local Bubble are the Loop II Bubble and the Loop III Bubble.
[edit] Observation
Launched in 2003 and active until 2008, a small space observatory mission called Cosmic Hot Interstellar Plasma Spectrometer (CHIPS or CHIPSat) looked for the Local Bubble.[3]
[edit] See also
[edit] References
- ^ a b Local Chimney and Superbubbles, Solstation.com
- ^ T. W. Berghoefer, D. Breitschwerdt (2002). "The origin of the young stellar population in the solar neighborhood - a link to the formation of the Local Bubble?". Astronomy and Astrophysics 390 (1): 299–306. arXiv:astro-ph/0205128v2. Bibcode 2002A&A...390..299B. doi:10.1051/0004-6361:20020627.
- ^ CHIPS - Berkeley University
[edit] Further reading
- Anderson, Mark (6 January 2007). "Don't stop till you get to the Fluff". The New Scientist 193 (2585): 26–30. doi:10.1016/S0262-4079(07)60043-8. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B83WY-4MRP266-1H&_user=10&_coverDate=01%2F06%2F2007&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=315e7b521445da099b8eed40f702bca1&searchtype=a.
- Lallement, R.; Welsh, B. Y.; Vergely, J. L.; Crifo, F.; Sfeir, D. (December 1, 2003). "3D mapping of the dense interstellar gas around the Local Bubble". Astronomy & Astrophysics 411 (3): 447–464. Bibcode 2003A&A...411..447L. doi:10.1051/0004-6361:20031214. http://www.aanda.org/index.php?Itemid=129&option=com_article&access=doi&doi=10.1051/0004-6361:20031214.
- "Near-Earth Supernovas". Science@NASA Headline News. NASA. January 6, 2003. http://science.nasa.gov/science-news/science-at-nasa/2003/06jan_bubble/.
- "A Breeze from the Stars". Science@NASA Headline News. NASA. December 17, 2004. http://science.nasa.gov/science-news/science-at-nasa/2004/17dec_heliumstream/.
[edit] External links
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