Local Interstellar Cloud

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Diagram of the local clouds of matter that Earth's solar system is moving through, with arrows indicating cloud motion.
Map showing the Sun located near the edge of the Local Interstellar Cloud and Alpha Centauri about 4 light-years away in the neighboring G-cloud complex

The Local Interstellar Cloud (or Local Fluff or LIC) is the interstellar cloud roughly 30 light years or 9.2 parsecs across through which the Earth's Solar System is currently moving. It is currently unknown if the Sun is embedded in the Local Interstellar Cloud, or in the region where the Local Interstellar Cloud is interacting with the neighboring G-cloud.[1] The Solar System is thought to have entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain within it for another 10,000 to 20,000 years. The cloud has a temperature of about 6,000 K,[2] about the same temperature as the surface of the Sun. However, its specific heat capacity is very low because it is not very dense, with 0.3 atoms per cubic centimeter; less dense than the average for the interstellar medium in the Milky Way (0.5 atoms/cm3), though six times denser than the gas in the Local Bubble (0.05 atoms/cm3) which surrounds the local cloud.[3][4] In comparison, Earth's atmosphere at the edge of space has 12 billion atoms per cubic centimeter, dropping to 52 million at 150 km.[5]

The cloud is flowing outwards from the Scorpius-Centaurus Association, a stellar association that is a star-forming region.[6]

In 2009, Voyager 2 data suggested that the magnetic strength of the local interstellar medium was much stronger than previously expected (3.7 to 5.5 μG, against previous estimates of 1.8 to 2.5 μG). The fact that the Local Interstellar Cloud is strongly magnetized could explain its continued existence despite the pressures exerted upon it by the winds that blew out the Local Bubble.[7]

The Local Interstellar Cloud's potential effects on Earth are prevented by the solar wind and the Sun's magnetic field.[2] This interaction with the heliosphere is under study by the Interstellar Boundary Explorer (IBEX), a NASA satellite mapping the boundary between the Solar System and interstellar space.

See also

References

  1. ↑ Gilster, Paul (September 1, 2010). "Into the Interstellar Void". Centauri Dreams. 
  2. ↑ 2.0 2.1 "Near-Earth Supernovas". NASA.gov. NASA Science. January 6, 2003. Retrieved February 1, 2011. 
  3. ↑ "Our Local Galactic Neighborhood". NASA.gov. Interstellar Probe Project. 2000. 
  4. ↑ Boulanger, F.; Cox, P.; Jones, A. P. (2000). "Course 7: Dust in the Interstellar Medium". In Casoli, F.; Lequeux, J.; David, F. Infrared Space Astronomy, Today and Tomorrow. Les Houches Physics School. Grenoble, France. August 3-28, 1998. 70. p. 251. Bibcode:2000isat.conf..251B. 
  5. ↑ "U.S. Standard Atmosphere, 1976". Thermal Protection Systems Expert and Material Properties Database. NASA.gov. September 27, 2000. Retrieved June 24, 2012. 
  6. ↑ "The Local Interstellar Cloud". NASA.gov. Astronomy Picture of the Day. February 2, 2010. Retrieved February 1, 2011. 
  7. ↑ Opher, M.; Alouani Bibi, F.; Toth, G.; Richardson, J. D.; Izmodenov, V. V.; Gombosi, T. I. (December 24/31, 2009). "A strong, highly-tilted interstellar magnetic field near the Solar System". Nature 462. doi:10.1038/nature08567. 

Further reading

Earth → Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Virgo Supercluster → Pisces–Cetus Supercluster Complex → Observable universe → Universe

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