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 among others, the Local Interstellar Cloud, which contains the Solar System, and the G-Cloud. It is at least 300 light years across 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).
The exceptionally sparse matter, namely gas, of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years and remains in an excited state, emitting in the X-ray band. It was once thought that the most likely candidate for the remains of this supernova was Geminga, a pulsar in the constellation Gemini. Later, however, it has been suggested that multiple supernovae in subgroup B1 of the Pleiades moving group were more likely responsible, becoming a remnant supershell.
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|Designations||Local Hot Bubble, LHB, Local Bubble, Local Interstellar Bubble|
The Solar System has been traveling through the region currently occupied by the Local Bubble for the last five to ten million years. Its current location lies in the Local Interstellar Cloud (LIC), a minor region of denser material within the Bubble. The LIC formed where the Local Bubble and the Loop I Bubble met. The gas within the LIC has a density of approximately 0.3 atoms per cubic centimeter.
The Local Bubble is not spherical, but seems to be narrower in the galactic plane, becoming somewhat egg-shaped or elliptical, and may widen above and below the galactic plane, becoming shaped like an hourglass. It abuts other bubbles of less dense interstellar medium (ISM), including, in particular, the Loop I Bubble. The Loop I Bubble was cleared, heated and maintained by supernovae and stellar winds in the Scorpius–Centaurus Association, some 500 light years from the Sun. The Loop I Bubble contains the star Antares (also known as Alpha Scorpii), as shown on the diagram above right. Several tunnels connect the cavities of the Local Bubble with the Loop I Bubble, called the "Lupus Tunnel". Other bubbles which are adjacent to the Local Bubble are the Loop II Bubble and the Loop III Bubble.
Launched in February 2003 and active until April 2008, a small space observatory called Cosmic Hot Interstellar Plasma Spectrometer (CHIPS or CHIPSat) examined the hot gas within the Local Bubble. The Local Bubble was also the region of interest for the Extreme Ultraviolet Explorer mission (1992–2001), which examined hot EUV sources within the bubble. Sources beyond the edge of the bubble were identified, but attenuated by the denser interstellar medium.
2MASS J154043.42−510135.7 (2M1540) is a red dwarf of spectral type M7, located in Norma at approximately 17 light-years from Earth. It was discovered in 2014. It is the nearest known M7 dwarf.AD Leonis
AD Leonis (Gliese 388) is a red dwarf star. It is located relatively near the Sun, at a distance of about 16 light years, in the constellation Leo. AD Leonis is a main sequence star with a spectral classification of M3.5V. It is a flare star that undergoes random increases in luminosity.DENIS J081730.0−615520
DENIS J081730.0−615520 (also known as 2MASS 08173001−6155158) is a T brown dwarf approximately 16 ly (4.9 pc) away in the constellation Carina. It was discovered by Etienne Artigau and his colleagues in April 2010. The star belongs to the T6 spectral class implying a photosphere temperature of about 950 K. It has a mass of about 15 MJ (Jupiter masses) or about 1.5% the mass of the Sun.DENIS J081730.0-615520 is the second-nearest isolated T dwarf to the Sun (after UGPS J0722−0540) and the fifth-nearest (also after ε Indi Bab and SCR 1845-6357B) if one takes into account T dwarfs in multiple star systems. It is also the brightest T dwarf in the sky (in the J-band); it had been missed before due to its proximity to the galactic plane.DEN 0255−4700
DENIS 0255−4700 is an extremely faint brown dwarf approximately 16 light years from the Solar System in the southern constellation of Eridanus. It is the closest isolated L brown dwarf (no undiscovered L dwarves are expected to be closer), and only after the binary Luhman 16. It is also the faintest brown dwarf (with the absolute magnitude of MV=24.44) having measured visible magnitude. A number of nearer T and Y-type dwarfs are known, specifically WISE 0855−0714, Epsilon Indi B and C, SCR 1845-6357 B, DEN 1048−3956, and UPGS 0722−05.DEN 1048−3956
DEN 1048−3956 is a brown dwarf about 13.1 light years from Earth in the southern constellation of Antlia, among the closest interstellar objects to Earth. This substellar object is very dim with an apparent magnitude of about 17, and will require a telescope with a camera to be seen. It was discovered in 2000 by Xavier Delfosse (Institute of Astrophysics of the Canary Islands, now Observatoire de Grenoble) and Thierry Forveille (Canada–France–Hawaii Telescope Corporation), with the assistance of nine other astronomers.
In 2005 a powerful flare from this object was detected by radio astronomy.EZ Aquarii
EZ Aquarii is a triple star system approximately 11.3 ly (3.5 pc) from the Sun in the constellation Aquarius. It is also known as Luyten 789-6 and Gliese 866 and all three components are M-type red dwarfs. The pair EZ Aquarii AC form a spectroscopic binary with a 3.8-day orbit and a 0.03 AU separation. This pair share an orbit with EZ Aquarii B that has an 823-day period. The A and B components of Luyten 789-6 together emit X-rays.The configuration of the inner binary pair may permit a circumbinary planet to orbit near their habitable zone. EZ Aquarii is approaching the Solar System and, in about 32,300 years, will be at its minimal distance of about 8.2 ly (2.5 pc) from the Sun. The ChView simulation shows that currently its nearest neighbouring star is Lacaille 9352 at about 4.1 ly (1.3 pc) from EZ Aquarii.Gliese 1002
Gliese 1002 is a red dwarf star. It is located relatively near our Sun, at a distance of about 15.8 light years, in the constellation Cetus.
This appears to be a relatively quiescent star, and no flare activity has been detected.Gliese 674
Not to be confused with Gliese 676.Gliese 674 (Gliese–Jahreiß 674) is a pre-main-sequence red dwarf approximately 15 light years away in the southern constellation of Ara.Gliese 687
Gliese 687, or GJ 687 (Gliese–Jahreiß 687) is a red dwarf in the constellation Draco. This is one of the closest stars to the Sun and lies at an approximate distance of less than 15 light years. Even though it is close by, it has a magnitude of about 9, so it can only be seen through a moderately sized telescope. Gliese 687 has a high proper motion, advancing 1.304 arcseconds per year across the sky. It has a net relative velocity of about 39 km/s. It is known to have a Neptune-mass planet.. In old books and articles it is refeered as Argelander Oeltzen 17415.LHS 288
LHS 288 (Luyten 143-23) is a red dwarf around 15.8 light years from the Sun, the closest in the constellation Carina (near Eta Carinae). It is far too faint to be seen with the unaided eye, with an apparent magnitude of 13.92.
Recent studies suggest it may harbour a planet with a mass as small as 2.4 Jupiter, but the possibility that it passed over an undetected faint star could not be eliminated.LHS 292
LHS 292 is a red dwarf in the constellation Sextans. It is far too faint to be seen with the unaided eye and requires a large amateur telescope to be seen visually. It lies relatively close to the Sun at a distance of about 14.8 light years. It is a flare star, which means it can suddenly increase in brightness for short periods of time.
It has the space velocity components [U, V, W] = [28, −16, −14] km/s.Luyten 726-8
Luyten 726-8, also known as Gliese 65, is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. Luyten 726-8B is also known under the variable star designation UV Ceti, being the archetype for the class of flare stars.Orion Arm
The Orion Arm is a minor spiral arm of the Milky Way some 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length, containing the Solar System, including the Earth. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion Bridge, and formerly, the Local Spur and Orion Spur.
The arm is named for the Orion constellation, which is one of the most prominent constellations of Northern Hemisphere winter (Southern Hemisphere summer). Some of the brightest stars and most famous celestial objects of the constellation (e.g. Betelgeuse, Rigel, the three stars of Orion's Belt, the Orion Nebula) are within it as shown on the interactive map below.
The arm is between the Carina–Sagittarius Arm (the local portions of which are toward the Galactic Center) and the Perseus Arm (the local portion of which is the main outer-most arm and one of two major arms of the galaxy).
Long thought to be a minor structure, namely a "spur" between the two arms mentioned, evidence was presented in mid 2013 that the Orion Arm might be a branch of the Perseus Arm, or possibly an independent arm segment.Within the arm, the Solar System is close to its inner rim, in a relative cavity in the arm's Interstellar Medium known as the Local Bubble, about halfway along the arm's length, approximately 8,000 parsecs (26,000 light-years) from the Galactic Center.Ross 154
Ross 154 (V1216 Sgr) is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44, making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of
6.5 cm (3 in) under ideal conditions. The distance to this star can be estimated from parallax measurements, which places it at 9.69 light-years (2.97 parsecs) away from Earth. It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.Teegarden's Star
Teegarden's Star (SO J025300.5+165258, 2MASS J02530084+1652532, LSPM J0253+1652) is an M-type red dwarf in the constellation Aries, about 12 light-years from the Solar System. Although it is near Earth it is a dim magnitude 15 and can only be seen through large telescopes. This star was found to have a very large proper motion of about 5 arcseconds per year. Only seven stars with such large proper motions are currently known.WISE 0350−5658
WISE J035000.32−565830.2 (designation abbreviated to WISE 0350−5658) is a brown dwarf of spectral class Y1, located in constellation Reticulum, the nearest known star/brown dwarf in this constellation. Being approximately 17.7 light-years from Earth, it is one of the Sun's nearest neighbors.WISE 0855−0714
WISE 0855−0714 (full designation WISE J085510.83−071442.5) is a sub-brown dwarf 2.23±0.04 parsecs (7.27±0.13 light-years) from Earth, the discovery of which was announced in April 2014 by Kevin Luhman using data from the Wide-field Infrared Survey Explorer (WISE). As of 2014, WISE 0855−0714 has the third-highest proper motion (8118±8 mas/yr) after Barnard's Star (10300 mas/yr) and Kapteyn's Star (8600 mas/yr) and the fourth-largest parallax (449±8 mas) of any known star or brown dwarf, meaning it is the fourth-closest extrasolar system to the Sun. It is also the coldest object of its type found in interstellar space, having a temperature in the range 225 to 260 K (−48 to −13 °C; −55 to 8 °F).Wolf 424
Wolf 424 is a binary star system comprising two red dwarf stars at a distance of approximately 14.2 light years from the Sun. It is located in the constellation Virgo, between the stars ε Virginis and ο Virginis.
The close binary nature of this star was discovered by Dutch American astronomer Dirk Reuyl in 1941, based upon an elongation of the star found in photographs. The two stars in the Wolf 424 system orbit about each other with a semi-major axis of 4.1 AU and an eccentricity of 0.3. The stars have an orbital period of 15.5 years and have a combined apparent magnitude of about 12.5.
Wolf 424A is a cool main sequence red dwarf star of approximately 0.14 solar masses (147 Jupiters) and a radius of 0.17 solar radii. Its companion, Wolf 424B, is a cool main sequence red dwarf star of approximately 0.13 solar masses (136 Jupiters) and a radius of 0.14 solar radii. They are two of the dimmest known objects within 15 light years of the Sun. In 1967, it was discovered that both are flare stars that undergo random increases in luminosity. The system has been designated FL Virginis, and may experience sunspot activity. The stars may undergo variation in the level of flare activity over periods lasting several years.YZ Ceti
YZ Ceti is a red dwarf star in the constellation Cetus. Although it is relatively close to the Sun at just 12 light years, this star cannot be seen with the naked eye. It is classified as a flare star that undergoes intermittent fluctuations in luminosity. YZ Ceti is about 13 percent the mass of the Sun and 17% of its radius.
This star is unusually close to Tau Ceti, a star of spectral class G8. The two are only about 1.6 light years apart, a little more than a third of the distance from the Sun to the Solar System's nearest neighbor, Proxima Centauri.
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