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The Local Interstellar Cloud (LIC), also known as the Local Fluff, is an
interstellar cloud An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. Put differently, an interstellar cloud is a denser-than-average region of the interstellar medium, the matter and radiation that exists in ...
roughly across, through which the
Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
is moving. This feature overlaps a region around the Sun referred to as the solar neighborhood. It is unknown whether the Sun is embedded in the Local Interstellar Cloud, or is in the region where the Local Interstellar Cloud is interacting with the neighboring G-Cloud. Like the G-Cloud and others, the LIC is part of the Very Local Interstellar Medium which begins where the
heliosphere The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interst ...
and interplanetary medium end, the furthest that probes have traveled.


Structure

The Solar System is located within a structure called the Local Bubble, a low-density region of the galactic
interstellar medium In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
. Within this region is the Local Interstellar Cloud (LIC), an area of slightly higher hydrogen density. It is estimated that the Solar System entered the LIC within the past 10,000 years. It is uncertain whether the Sun is still inside of the LIC or has already entered a transition zone between the LIC and the G cloud. A recent analysis estimates the Sun will completely exit the LIC in no more than 1900 years. The cloud has a temperature of about , about the same temperature as the surface of the Sun. However, its
specific heat capacity In thermodynamics, the specific heat capacity (symbol ) of a substance is the heat capacity of a sample of the substance divided by the mass of the sample, also sometimes referred to as massic heat capacity. Informally, it is the amount of heat t ...
is very low because it is not very dense, with . This is less dense than the average for the interstellar medium in the
Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked ey ...
(), though six times denser than the gas in the hot, low-density Local Bubble () which surrounds the local cloud. In comparison,
Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...
at the edge of space has around 1.2 molecules per cubic centimeter, dropping to around 50 million (5.0) at . As an underdensity, it may be more instructive to refer to as a void than a cloud. The cloud is flowing outwards from the
Scorpius–Centaurus association The Scorpius–Centaurus association (sometimes called Sco–Cen or Sco OB2) is the nearest OB association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus–Lupus, and Lower Centaurus–Cru ...
, a
stellar association A stellar association is a very loose star cluster, looser than both open clusters and globular clusters. Stellar associations will normally contain from 10 to 100 or more stars. The stars share a common origin, but have become gravitationally ...
that is a star-forming region, roughly perpendicular to the Sun's own direction, if assumed to be two dimensional. In 2019, researchers found interstellar iron-60 (60Fe) in
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest co ...
, which they relate to the Local Interstellar Cloud.


Interaction with solar magnetic field

In 2009, ''
Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, ''Voyager 1'', on ...
'' data suggested that the magnetic strength of the local interstellar medium was much stronger than expected (370 to 550 pico teslas (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. The Local Interstellar Cloud's potential effects on Earth are greatly diminished by the
solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the ...
and the Sun's magnetic field. This interaction with the
heliosphere The heliosphere is the magnetosphere, astrosphere and outermost atmospheric layer of the Sun. It takes the shape of a vast, bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding interst ...
is under study by the Interstellar Boundary Explorer (IBEX), a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...
satellite mapping the boundary between the Solar System and interstellar space.


See also

* Gould Belt * List of nearest stars and brown dwarfs *
List of nearby stellar associations and moving groups This is a list of nearby stellar associations and moving groups. A stellar association is a very loose star cluster, looser than an open cluster. A moving group is the remnant of such a stellar association. Members of stellar associations an ...
* Orion Arm * Perseus Arm *
Voyager program The Voyager program is an American scientific program that employs two robotic interstellar probes, '' Voyager 1'' and '' Voyager 2''. They were launched in 1977 to take advantage of a favorable alignment of Jupiter and Saturn, to fly near ...
– probes left heliosphere in the 2010s


References


Further reading


"A Breeze from the Stars"
at NASA Science
"Voyager Makes an Interstellar Discovery"
at NASA Science

*


External links

* {{Portal bar, Stars, Spaceflight, Solar System, Science