Local Interstellar Cloud
Diagram of the local clouds of matter that Earth's solar system is moving through, with arrows indicating cloud motion.
|Distance||0 ly (0 pc)|
|Radius||15 ly (4.6 pc)|
|Designations||Local Cloud, LIC|
|See also: Lists of nebulae|
The Local Interstellar Cloud (or Local Fluff or LIC) is the interstellar cloud roughly 30 light-years (9.2 pc) 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. 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 6,000 K (5,730 °C; 10,340 °F), 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. In comparison, Earth's atmosphere at the edge of space has around 1.2×1013 molecules per cubic centimeter, dropping to around 50 million at 450 km (280 mi).
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.
The Local Interstellar Cloud's potential effects on Earth are prevented by the solar wind and the Sun's magnetic field. 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.
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