Local Interstellar Cloud

Local Interstellar Cloud
Interstellar cloud

Diagram of the local clouds of matter that the Solar System is moving through, with arrows indicating cloud motion.
Observation data
Distance 0[1] ly   (0[1] pc)
Physical characteristics
Radius 15 ly   (4.6 pc)
Designations Local Cloud, LIC
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 (LIC), also known as the Local Fluff, is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the 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.[2]

Structure

The Solar System is thought to have entered the Local Interstellar Cloud at some point 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 7,000 K (6,730 °C; 12,140 °F),[3] 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.[4][5] In comparison, Earth's atmosphere at the edge of space has around 1.2×1013 molecules per cubic centimeter, dropping to around 50 million (5.0×107) at 450 km (280 mi).[6]

The cloud is flowing outwards from the Scorpius–Centaurus Association, a stellar association that is a star-forming region.[7]

In 2009, Voyager 2 data suggested that the magnetic strength of the local interstellar medium was much stronger than expected (370 to 550 picoteslas (pT), against previous estimates of 180 to 250 pT). 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.[8]

The Local Interstellar Cloud's potential effects on Earth are prevented by the solar wind and the Sun's magnetic field.[3] 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. 1 2 "NAME LIC -- Cloud". SIMBAD. Retrieved 15 March 2014.
  2. ↑ Gilster, Paul (September 1, 2010). "Into the Interstellar Void". Centauri Dreams.
  3. 1 2 "Near-Earth Supernovas". NASA.gov. NASA Science. January 6, 2003. Retrieved February 1, 2011.
  4. ↑ "Our Local Galactic Neighborhood". NASA.gov. Interstellar Probe Project. 2000.
  5. ↑ 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.
  6. ↑ United States Committee on Extension to the Standard Atmosphere (October 1976). U.S. Standard Atmosphere, 1976. NOAA, NASA and U.S. Air Force. pp. 210–215. OCLC 3360756.
  7. ↑ Nemiroff, R.; Bonnell, J., eds. (February 2, 2010). "The Local Interstellar Cloud". Astronomy Picture of the Day. NASA. Retrieved February 1, 2011.
  8. ↑ 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" (PDF). Nature. 462. Bibcode:2009Natur.462.1036O. doi:10.1038/nature08567.

Further reading

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