G-Cloud

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G-Cloud
Interstellar cloud
The Local Interstellar Cloud and neighboring G-cloud complex.svg
The G-Cloud complex and neighboring Local Interstellar Cloud
Observation data
DesignationsG Cloud [1]
See also: Lists of nebulae

The Galactic (G) cloud or G cloud, [2] also known as the G-Cloud (or G-Cloud complex) is an interstellar cloud located next to the Local Interstellar Cloud, within the Local Bubble. It is unknown whether the Solar System is embedded in the Local Interstellar Cloud or in the region where the two clouds are interacting, although the Solar System is currently moving towards the G-Cloud. The G-Cloud contains the stars Alpha Centauri (a triple star system that includes Proxima Centauri) and Altair (and possibly others). [3] [4] [5] [6] [7] [8]

Estimates for the n(H I) particle density in the direction of Alpha Centauri. were made in 2011 by Crawford [9] as 0.1 cm−3 and in 2014 by Gry [10] as 0.098 cm−3.

Related Research Articles

<span class="mw-page-title-main">Molecular cloud</span> Type of interstellar cloud

A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, H2), and the formation of H II regions. This is in contrast to other areas of the interstellar medium that contain predominantly ionized gas.

<span class="mw-page-title-main">Star formation</span> Process by which dense regions of molecular clouds in interstellar space collapse to form stars

Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. As a branch of astronomy, star formation includes the study of the interstellar medium (ISM) and giant molecular clouds (GMC) as precursors to the star formation process, and the study of protostars and young stellar objects as its immediate products. It is closely related to planet formation, another branch of astronomy. Star formation theory, as well as accounting for the formation of a single star, must also account for the statistics of binary stars and the initial mass function. Most stars do not form in isolation but as part of a group of stars referred as star clusters or stellar associations.

<span class="mw-page-title-main">Proxima Centauri</span> Star in the constellation Centaurus

Proxima Centauri is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the 'nearest [star] of Centaurus'. It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude of 11.13, it is too faint to be seen with the unaided eye. Proxima Centauri is a member of the Alpha Centauri star system, being identified as component Alpha Centauri C, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.

<span class="mw-page-title-main">Local Bubble</span> Cavity in the interstellar medium which contains the Local Interstellar Cloud

The Local Bubble, or Local Cavity, is a relative cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way. It contains the closest of celestial neighbours and among others, the Local Interstellar Cloud, the neighbouring G-Cloud, the Ursa Major moving group and the Hyades. It is estimated to be at least 1000 light years in size, and is defined by its neutral-hydrogen density of about 0.05 atoms/cm3, or approximately one tenth of the average for the ISM in the Milky Way (0.5 atoms/cm3), and one sixth that of the Local Interstellar Cloud (0.3 atoms/cm3).

<span class="mw-page-title-main">Sagittarius A*</span> Black hole at the center of the Milky Way

Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.

<span class="mw-page-title-main">Messier 56</span> Globular cluster in the constellation Lyra

Messier 56 is a globular cluster in the constellation Lyra. It was discovered by Charles Messier in 1779. It is angularly found about midway between Albireo and Sulafat. In a good night sky it is tricky to find with large (50–80 mm) binoculars, appearing as a slightly fuzzy star. The cluster can be resolved using a telescope with an aperture of 8 in (20 cm) or larger.

<span class="mw-page-title-main">Extinction (astronomy)</span> Interstellar absorption and scattering of light

In astronomy, extinction is the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer. Interstellar extinction was first documented as such in 1930 by Robert Julius Trumpler. However, its effects had been noted in 1847 by Friedrich Georg Wilhelm von Struve, and its effect on the colors of stars had been observed by a number of individuals who did not connect it with the general presence of galactic dust. For stars lying near the plane of the Milky Way which are within a few thousand parsecs of the Earth, extinction in the visual band of frequencies is roughly 1.8 magnitudes per kiloparsec.

<span class="mw-page-title-main">Local Interstellar Cloud</span> Interstellar cloud in the Milky Way Galaxy

The Local Interstellar Cloud (LIC), also known as the Local Fluff, is an interstellar cloud roughly 30 light-years (9.2 pc) across, through which the Solar System is moving. This feature overlaps with 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 and interplanetary medium end, the furthest that probes have traveled.

<span class="mw-page-title-main">Iota Centauri</span> Star in the constellation Centaurus

Iota Centauri, Latinized from ι Centauri, is a star in the southern constellation of Centaurus. Based upon parallax measurements, it lies at a distance of approximately 58.6 light-years from Earth. Iota Centauri has an apparent visual magnitude of +2.73, making it easily visible to the naked eye.

Xi<sup>1</sup> Centauri Star in the constellation Centaurus

Xi1 Centauri, Latinized from ξ1 Centauri, is a solitary star in the southern constellation of Centaurus. It is visible to the naked eye with an apparent visual magnitude of +4.83. With an annual parallax shift of 14.79 mas, it is located around 221 light years from the Sun. At that distance, the apparent visual magnitude of the star is diminished by an interstellar extinction factor of 0.10 due to intervening dust. Just 17 arc minutes to the east of Xi1 Centauri lies the galaxy NGC 4945.

<span class="mw-page-title-main">NGC 5286</span> Globular cluster in the constellation Centaurus

NGC 5286 is a globular cluster of stars located some 35,900 light years away in the constellation Centaurus. At this distance, the light from the cluster has undergone reddening from interstellar gas and dust equal to E(B – V) = 0.24 magnitude in the UBV photometric system. The cluster lies 4 arc-minutes north of the naked-eye star M Centauri. It was discovered by Scottish astronomer James Dunlop, active in Australia, and listed in his 1827 catalog.

<span class="mw-page-title-main">Exocomet</span> Comet outside the Solar System

An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.

<span class="mw-page-title-main">Proxima Centauri b</span> Terrestrial planet orbiting Proxima Centauri

Proxima Centauri b, sometimes referred to as Alpha Centauri Cb, is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of the larger triple star system Alpha Centauri. It is about 4.2 light-years from Earth in the constellation Centaurus, making it and Proxima d, along with the currently-disputed Proxima c, the closest known exoplanets to the Solar System.

The Local Leo Cold Cloud is a relatively nearby cloud of interstellar gas. It ranges from 11.3 to 24.3 parsecs in distance. The cloud's neutral gas temperature is around 20K, which is cold compared to the 1,000,000K temperature of the Local Bubble in which it is embedded. The hydrogen atom density in this cloud is 3,000 atoms per cubic centimeter, which is dense for interstellar medium. Thermal infrared radiation from dust in the cloud can be detected at 0.1 mm.

<span class="mw-page-title-main">HD 73882</span> Eclipsing binary system in constellation Vela

HD 73882 is a visual binary system with the components separated by 0.6″ and a combined spectral class of O8. One of stars is an eclipsing binary system. The period of variability is listed as both 2.9199 days and 20.6 days, possibly due to the secondary being a spectroscopic binary star.

References

  1. "NAME G Cloud". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 15 March 2014.
  2. Swaczyna, Paweł; Schwadron, Nathan A.; Möbius, Eberhard; Bzowski, Maciej; Frisch, Priscilla C.; Linsky, Jeffrey L.; McComas, David J.; Rahmanifard, Fatemeh; Redfield, Seth; Winslow, Réka M.; Wood, Brian E.; Zank, Gary P. (1 October 2022). "Mixing Interstellar Clouds Surrounding the Sun". The Astrophysical Journal Letters. 937 (2): L32. arXiv: 2209.09927 . Bibcode:2022ApJ...937L..32S. doi: 10.3847/2041-8213/ac9120 . ISSN   2041-8205.
  3. "Our Local Galactic Neighborhood". Interstellar.jpl.nasa.gov. Archived from the original on 21 November 2013. Retrieved 7 October 2015.
  4. Paul Gilster (1 September 2010). "Into the Interstellar Void". Centauri-dreams.org.
  5. "The Interstellar Medium". Archived from the original on 19 April 2012. Retrieved 22 October 2012.
  6. Seth Redfield (2009). "Physical Properties of the Local Interstellar Medium" (PDF). Igpp.ucla.edu.
  7. Frisch., Priscilla (3 February 2003). "Local Interstellar Matter: The Apex Cloud". The Astrophysical Journal. 593 (2): 868–873. arXiv: astro-ph/0302037 . Bibcode:2003ApJ...593..868F. doi:10.1086/376684. S2CID   7087871.
  8. "Short Sharp Science: Spacecraft probes gas cloud swaddling the solar system". Newscientist.com. 2 February 2012.
  9. Crawford, Ian A. (1 April 2011). "Project Icarus: A review of local interstellar medium properties of relevance for space missions to the nearest stars". Acta Astronautica. 68 (7): 691–699. arXiv: 1010.4823 . Bibcode:2011AcAau..68..691C. doi:10.1016/j.actaastro.2010.10.016. ISSN   0094-5765. S2CID   101553.
  10. Gry, Cécile; Jenkins, Edward B. (July 2014). "The interstellar cloud surrounding the Sun: a new perspective". Astronomy & Astrophysics. 567: A58. arXiv: 1404.0326 . Bibcode:2014A&A...567A..58G. doi:10.1051/0004-6361/201323342. ISSN   0004-6361. S2CID   118571335.