Superbubble

A superbubble or supershell is a cavity which is hundreds of light years across and is populated with hot (106 K) gas atoms, less dense than the surrounding interstellar medium, blown against that medium and carved out by multiple supernovae and stellar winds. The winds, passage and gravity of newly born stars strip superbubbles of any other dust or gas.[2] The Solar System lies near the center of an old superbubble, known as the Local Bubble, whose boundaries can be traced by a sudden rise in dust extinction of exterior stars at distances greater than a few hundred light years.

Superbubble N70 in LMC
The superbubble Henize 70, also known as N70 or DEM301, in the Large Magellanic Cloud[1]

Formation

The most massive stars, with masses ranging from eight to roughly one hundred solar masses and spectral types of O and early B, are usually found in groups called OB associations. Massive O stars have strong stellar winds, and most of these stars explode as supernovae at the end of their lives.

The strongest stellar winds release kinetic energy of 1051 ergs (1044 J) over the lifetime of a star, which is equivalent to a supernova explosion. These winds can form stellar wind bubbles dozens of light years across.[3] Inside OB associations, the stars are close enough that their wind bubbles merge, forming a giant bubble called a superbubble. When stars die, supernova explosions, similarly, drive blast waves that can reach even larger sizes, with expansion velocities up to several hundred km s−1. Stars in OB associations are not gravitationally bound, but they drift apart at small speeds (of around 20 km s−1), and they exhaust their fuel rapidly (after a few millions of years). As a result, most of their supernova explosions occur within the cavity formed by the stellar wind bubbles.[4][5] These explosions never form a visible supernova remnant, but instead expend their energy in the hot interior as sound waves. Both stellar winds and stellar explosions thus power the expansion of the superbubble in the interstellar medium.

The interstellar gas swept up by superbubbles generally cools, forming a dense shell around the cavity. These shells were first observed in line emission at twenty-one centimeters from hydrogen,[6] leading to the formulation of the theory of superbubble formation. They are also observed in X-ray emission from their hot interiors, in optical line emission from their ionized shells, and in infrared continuum emission from dust swept up in their shells. X-ray and visible emission are typically observed from younger superbubbles, while older, larger objects seen in twenty-one centimeters may even result from multiple superbubbles combining, and so are sometimes distinguished by calling them supershells.

Large enough superbubbles can blow through the entire galactic disk, releasing their energy into the surrounding galactic halo or even into the intergalactic medium.[7][8]

Examples

Superbubble LHA 120-N 44 in the Large Magellanic Cloud
Very Large Telescope image of superbubble LHA 120-N 44 in the Large Magellanic Cloud. Credit: ESO/Manu Mejias.

References

  1. ^ a b Henize 70: A SuperBubble In The LMC, Astronomy Picture of the Day, 1999-11-30
  2. ^ Thomson, Jason (2016-05-18). "Sublime image reveals superbubbles, star formation, and satellite galaxies". Retrieved 2016-10-03.
  3. ^ Castor, J.; McCray, R.; Weaver, R. (1975). "Interstellar Bubbles". Astrophysical Journal Letters. 200: L107–L110. Bibcode:1975ApJ...200L.107C. doi:10.1086/181908.
  4. ^ Tomisaka, K.; Habe, A.; Ikeuchi, S. (1981). "Sequential explosions of supernovae in an OB association and formation of a superbubble". Astrophys. Space Sci. 78 (2): 273–285. Bibcode:1981Ap&SS..78..273T. doi:10.1007/BF00648941.
  5. ^ McCray, R.; Kafatos, M. (1987). "Supershells and Propagating Star Formation". Astrophys. J. 317: 190–196. Bibcode:1987ApJ...317..190M. doi:10.1086/165267.
  6. ^ Heiles, C. (1979). "H I shells and supershells". Astrophys. J. 229: 533–544. Bibcode:1979ApJ...229..533H. doi:10.1086/156986.
  7. ^ Tomisaka, K.; Ikeuchi, S. (1986). "Evolution of superbubble driven by sequential supernova explosions in a plane-stratified gas distribution". Publ. Astron. Soc. Jpn. 38: 697–715. Bibcode:1986PASJ...38..697T.
  8. ^ Mac Low, M.-M.; McCray, R. (1988). "Superbubbles in Disk Galaxies". Astrophys. J. 324: 776–785. Bibcode:1988ApJ...324..776M. doi:10.1086/165936.
  9. ^ "A Cosmic Superbubble". ESO Photo Release. Retrieved 20 July 2011.
  10. ^ Nemiroff, R.; Bonnell, J., eds. (6 February 2006). "N44 Superbubble". Astronomy Picture of the Day. NASA.
  11. ^ Monogem Ring, The Internet Encyclopedia of Science
  12. ^ Yurii Pidopryhora, Felix J. Lockman, and Joseph C. Shields. The Ophiuchus Superbubble: A Gigantic Eruption from the Inner Disk of the Milky Way, The Astrophysical Journal 656:2, 928-942 (2007)
  13. ^ "Huge 'Superbubble' of Gas Blowing Out of Milky Way". PhysOrg.com. 2006-01-13. Retrieved 2008-07-04.
  14. ^ STIS and GHRS Observations of Warm and Hot Gas Overlying the Scutum Supershell (GS 018−04+44), The Astrophysical Journal
  15. ^ Observational Evidence of Supershell Blowout in GS 018-04+44: The Scutum Supershell, The Astrophysical Journal, Volume 532, Issue 2, pp. 943–969.

External links

Advanced Composition Explorer

Advanced Composition Explorer (ACE) is a NASA Explorers program Solar and space exploration mission to study matter comprising energetic particles from the solar wind, the interplanetary medium, and other sources.

Real-time data from ACE is used by the NOAA Space Weather Prediction Center to improve forecasts and warnings of solar storms. The ACE robotic spacecraft was launched August 25, 1997, and entered a Lissajous orbit close to the L1 Lagrangian point (which lies between the Sun and the Earth at a distance of some 1.5 million km from the latter) on December 12, 1997. The spacecraft is currently operating at that orbit. Because ACE is in a non-Keplerian orbit, and has regular station-keeping maneuvers, the orbital parameters in the adjacent information box are only approximate.

As of 2019, the spacecraft is still in generally good condition, and is projected to have enough propellant to maintain its orbit until 2024. NASA Goddard Space Flight Center managed the development and integration of the ACE spacecraft.

Anticenter shell

The anticenter shell or anticenter superbubble is a region near the anticenter of the Milky Way Galaxy that emits 21 cm radiation. It is located at 06h 27m +15°, or l = 197°, b = +2° in galactic coordinates, near the border of the constellations Gemini and Orion. It is a supershell (a very large superbubble) within our galaxy that is spherical in shape and features jets of gas.

Discovered in 1970, this galactic object has subsequently been variously classified by researchers as a spiral arm of the Milky Way in 1972, a nearby tidally-stripped dwarf galaxy in 1975, and a high-velocity cloud in 1979.The name Snickers for the anticenter shell arose from the description in 1975 by Christian Simonson, a University of Maryland astronomer who believed it to be a small "peanut" of a galaxy just outside the Milky Way.

Simonson's colleagues coined the name Snickers (in reference to the American chocolate bars Milky Way and Snickers) due to its proximity to the Milky Way. Less popularly, the anticenter superbubble is also referred to as 0627-15 from its equatorial coordinates.The anticenter shell is approximately 55,000 light years (17 kpc) from the sun. Its dimensions are difficult to determine by radio observation due to its location near the Zone of Avoidance, the regions of the sky obscured by interstellar dust along the galactic equator.

Astrophysical X-ray source

Astrophysical X-ray sources are astronomical objects with physical properties which result in the emission of X-rays.

There are a number of types of astrophysical objects which emit X-rays, from galaxy clusters, through black holes in active galactic nuclei (AGN) to galactic objects such as supernova remnants, stars, and binary stars containing a white dwarf (cataclysmic variable stars and super soft X-ray sources), neutron star or black hole (X-ray binaries). Some solar system bodies emit X-rays, the most notable being the Moon, although most of the X-ray brightness of the Moon arises from reflected solar X-rays. A combination of many unresolved X-ray sources is thought to produce the observed X-ray background. The X-ray continuum can arise from bremsstrahlung, either magnetic or ordinary Coulomb, black-body radiation, synchrotron radiation, inverse Compton scattering of lower-energy photons by relativistic electrons, knock-on collisions of fast protons with atomic electrons, and atomic recombination, with or without additional electron transitions.Furthermore, celestial entities in space are discussed as celestial X-ray sources. The origin of all observed astronomical X-ray sources is in, near to, or associated with a coronal cloud or gas at coronal cloud temperatures for however long or brief a period.

Dorado

Dorado (English pronunciation: ) is a constellation in the southern sky. It was named in the late 16th century and is now one of the 88 modern constellations. Its name refers to the dolphinfish (Coryphaena hippurus), which is known as dorado in Portuguese, although it has also been depicted as a swordfish. Dorado contains most of the Large Magellanic Cloud, the remainder being in the constellation Mensa. The South Ecliptic pole also lies within this constellation.

Even though the name Dorado is not Latin but Portuguese, astronomers give it the Latin genitive form Doradus when naming its stars; it is treated (like the adjacent asterism Argo Navis) as a feminine proper name of Greek origin ending in -ō (like Io or Callisto or Argo), which have a genitive ending -ūs.

Green Bank Telescope

The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world's largest fully steerable radio telescope. The Green Bank site was part of the National Radio Astronomy Observatory (NRAO) until September 30, 2016. Since October 1, 2016, the telescope has been operated by the newly separated Green Bank Observatory. The telescope honors the name of the late Senator Robert C. Byrd who represented West Virginia and who pushed the funding of the telescope through Congress.

The Green Bank Telescope operates at meter to millimeter wavelengths. Its 100-meter diameter collecting area, unblocked aperture, and good surface accuracy provide superb sensitivity across the telescope's full 0.1–116 GHz operating range. The GBT is fully steerable, and 85% of the entire local celestial hemisphere is accessible. It is used for astronomy about 6500 hours every year, with 2000–3000 hours per year going to high-frequency science. Part of the scientific strength of the GBT is its flexibility and ease of use, allowing for rapid response to new scientific ideas. It is scheduled dynamically to match project needs to the available weather. The GBT is also readily reconfigured with new and experimental hardware. The high-sensitivity mapping capability of the GBT makes it a necessary complement to the Atacama Large Millimeter Array, the Expanded Very Large Array, the Very Long Baseline Array, and other high-angular resolution interferometers. Facilities of the Green Bank Observatory are also used for other scientific research, for many programs in education and public outreach, and for training students and teachers.

The telescope began regular science operations in 2001, making it one of the newest astronomical facilities of the US National Science Foundation. It was constructed following the collapse of a previous telescope at Green Bank, a 90.44 m paraboloid erected in 1962. The previous telescope collapsed on 15 November 1988 due to the sudden loss of a gusset plate in the box girder assembly, which was a key component for the structural integrity of the telescope.

Karl Gordon Henize

Karl Gordon Henize, Ph.D. (; 17 October 1926 – 5 October 1993) was an American astronomer, space scientist, NASA astronaut, and professor at Northwestern University. He was stationed at several observatories around the world, including McCormick Observatory, Lamont-Hussey Observatory (South Africa), Mount Wilson Observatory, Smithsonian Astrophysical Observatory and Mount Stromlo Observatory (Australia). He was a member of the astronaut support crew for Apollo 15 and Skylab 2, 3, and 4. As a mission specialist on the Spacelab-2 mission (STS-51-F), he flew on Space Shuttle Challenger in July/August 1985. He was awarded the NASA Exceptional Scientific Achievement Medal in 1974.

He died in 1993, during a Mount Everest expedition while testing equipment for NASA.

LHA 120-N 55

LHA 120-N 55 is an emission nebula located within the Large Magellanic Cloud (LMC). It is a glowing clump of gas and dust that gets its light output from the hydrogen atoms shedding electrons within it. It was named in 1956, in a catalogue of H-alpha emission line objects in the LMC.

Local Bubble

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.

Loop I Bubble

The Loop I Bubble is a cavity in the interstellar medium (ISM) of the Orion Arm of the Milky Way. From our Sun's point of view, it is situated towards the Galactic Center of the Milky Way galaxy. Two conspicuous tunnels connect the Local Bubble with the Loop I Bubble cavity (the Lupus Tunnel). The Loop I Bubble is a supershell.The Loop I Bubble is located roughly 100 parsecs, or 330 light years, from the Sun. The Loop I Bubble was created 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). Several tunnels connect the cavities of the Local Bubble with the Loop I Bubble, called the "Lupus Tunnel".

N11 (emission nebula)

N11 (also known as LMC N11, LHA 120-N 11) is the brightest emission nebula in the north-west part of the Large Magellanic Cloud in the Dorado constellation. The N11 complex is the second largest H II region of the Large Magellanic Cloud after the Tarantula Nebula. It covers an area of approximately 6 arc minutes across. It has an elliptical shape and consists of a large bubble surrounded by nine large nebulae. It was named by Karl Henize in 1956.When close-up, the nebula has pink clouds of glowing gas which resembles candy floss. It has been well studied over the years and extends 1,000 light-years across.Its particularly notable features include a huge cavity measuring 80 by 60 pc and a five million year old central cluster (NGC 1761). It is surrounded by several ionized clouds where young O stars are forming. Several massive stars are included within LMC-N11, including LH 9, LH 10, LH 13, LH 14. It includes a supernova remnant N11L. In the very centre of NGC 1761 is a bright multiple star HD 32228 which contains a rare blue Wolf-Rayet star, type WC5 or WC6, and an O-type bright giant.The brightest nebulosity within N11 is the northern region N11B (NGC 1763), also known as the Bean Nebula because of its shape. On the north-east edge of N11B is the more compact N11A, known as the Rose Nebula, which has rose-like petals of gas and dust and are illuminated due to the massive hot stars within its centre. It is also known as IC 2116 and was catalogued as a star HD 32340. The east side of the N11 complex is N11C (NGC 1769), an emission nebula containing at least two compact open clusters. Outside the main "bubble" of N11 to the northeast is N11E, also known as NGC 1773, a small bright nebula containing several massive young stars. The south portion of the bubble is N11F, also called NGC 1760. The western portion of the bubble is faint and poorly-defined.To the south-west of N11 is the 7th magnitude red giant HD 31754, a foreground object. Close to it is the open cluster NGC 1733. There are three more distant galaxies west of N11: the pair PGC 16243 and PGC 16244; and LEDA 89996. To the south of them lies NGC 1731 and TYC 8889-619-1 which are part of the LMC N4 complex. The bright globular cluster NGC 1783 lies to the north of N11.

N44 (emission nebula)

N44 is an emission nebula with superbubble structure located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way in the constellation Dorado. Originally catalogued in Karl Henize's "Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds" of 1956, it is approximately 1,000 light-years wide and 160,000-170,000 light-years distant. N44 has a smaller bubble structure inside known as N44F. The superbubble structure of N44 itself is shaped by the radiation pressure of a 40-star group located near its center; the stars are blue-white, very luminous, and incredibly powerful. N44F has been shaped in a similar manner; it has a hot, massive central star with an unusually powerful stellar wind that moves at 7 million kilometers per hour. This is because it loses material at 100 million times the rate of the Sun, or approximately 1,000,000,000,000,000 tons per year. However, varying density in the N44 nebula has caused the formation of several dust pillars that may conceal star formation. This variable density is likely caused by previous supernovae in the vicinity of N44; many of the stars that have shaped it will eventually also end as supernovae. The past effects of supernovae are also confirmed by the fact that N44 emits x-rays.N44 is classified as an emission nebula because it contains large regions of ionized hydrogen. However, the three strongest emission lines in the nebula are singly ionized oxygen atoms, which emit at an ultraviolet wavelength of 372.7 nm, doubly-ionized oxygen atoms, which emit at a blue-green wavelength of 500.7 nm, and neutral hydrogen atoms, which emit the hydrogen-alpha line at a red wavelength of 656.2 nm.

NGC 1929

NGC 1929 (also known as ESO 56-EN107) is an open cluster associated with the emission nebula located within the N44 nebula in the Dorado constellation and part of the Large Magellanic Cloud. It was discovered by James Dunlop on August 3 1826. Its apparent magnitude is 14.0, and its size is 0.8 arc minutes.

NGC 2366

NGC 2366 is a Magellanic barred irregular dwarf galaxy located in the constellation Camelopardalis.There has been confusion about the various components of NGC 2366 and its neighbouring galaxy NGC 2363. At the southern end of NGC 2366 is the large, luminous HII region known as Markarian 71 (Mrk 71).To the west of Mrk 71 is another dwarf galaxy NGC 2363 which is interacting with NGC 2366. Corwins' notes remarks that there are two galaxies with two NGC numbers clearly attached to each one. "We shall just have to get used to calling the HII region "Markarian 71" (or one of its other names) since it is not N2363 as we've thought all these years."Within the region known as Mrk 71, there are two super star clusters (SSC) which are named 'A' and 'B' or 'Knot A' and 'Knot B'.Other names for the above components include: NGC 2366-I, NGC 2366-II, NGC 2366-III, NGC2366-A, NGC 2366-B, NGC 2366-C, NGC 2363-A, NGC 2363-B.NGC 2366 is an outlying member of the M81 Group.

NGC 3859

NGC 3859 is a spiral galaxy located about 295 million light-years away in the constellation Leo. It was discovered by astronomer Édouard Stephan on March 23, 1884. The galaxy is a member of the Leo Cluster.

Ophiuchus

Ophiuchus () is a large constellation straddling the celestial equator. Its name is from the Greek Ὀφιοῦχος Ophioukhos; "serpent-bearer", and it is commonly represented as a man grasping a snake (Unicode U+26CE ⛎). The serpent is represented by the constellation Serpens. Ophiuchus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. It was formerly referred to as Serpentarius and Anguitenens.

Orion–Eridanus Superbubble

The Orion–Eridanus Superbubble, or Eridanus Soft X-ray Enhancement is a superbubble located west of the Orion Nebula. The region is formed from overlapping supernova remnants that may be associated with the Orion OB1 stellar association; the bubble is approximately 1200 ly across. It is the nearest superbubble to the Local Bubble containing the Sun, with the respective shock fronts being about 500 ly apart.The structure was discovered from 21 cm radio observations by Carl Heiles and interstellar optical emission line observations by Reynolds and Ogden in the 1970s.

Super bubble

Super bubble may refer to:

Superbubble, an astronomical term for a large low-density region of the interstellar medium created by stellar winds

Super Bubble, a brand of bubble gum

Super Bubble Pop, a video game

Super Bubble Bobble, an advanced mode in the game Bubble Bobble

Supernova remnant

A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.

There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, and collapsing inward under the force of its own gravity to form a neutron star or a black hole; or a white dwarf star may accrete material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion.

In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light (or approximately 30,000 km/s). These ejecta are highly supersonic: assuming a typical temperature of the interstellar medium of 10,000 K, the Mach number can initially be > 1000. Therefore, a strong shock wave forms ahead of the ejecta, that heats the upstream plasma up to temperatures well above millions of K. The shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecs before its speed falls below the local sound speed.

One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was observed in February 1987. Other well-known supernova remnants include the Crab Nebula; Tycho, the remnant of SN 1572, named after Tycho Brahe who recorded the brightness of its original explosion; and Kepler, the remnant of SN 1604, named after Johannes Kepler. The youngest known remnant in our galaxy is G1.9+0.3, discovered in the galactic center.

X-ray astronomy

X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. X-ray astronomy is the space science related to a type of space telescope that can see farther than standard light-absorption telescopes, such as the Mauna Kea Observatories, via x-ray radiation.

X-ray emission is expected from astronomical objects that contain extremely hot gases at temperatures from about a million kelvin (K) to hundreds of millions of kelvin (MK). Moreover, the maintenance of the E-layer of ionized gas high in the Earth's Thermosphere also suggested a strong extraterrestrial source of X-rays. Although theory predicted that the Sun and the stars would be prominent X-ray sources, there was no way to verify this because Earth's atmosphere blocks most extraterrestrial X-rays. It was not until ways of sending instrument packages to high altitude were developed that these X-ray sources could be studied.

The existence of solar X-rays was confirmed early in the rocket age by V-2s converted to sounding rocket purpose, and the detection of extraterrestrial X-rays has been the primary or secondary mission of multiple satellites since 1958. The first cosmic (beyond the solar system) X-ray source was discovered by a sounding rocket in 1962. Called Scorpius X-1 (Sco X-1) (the first X-ray source found in the constellation Scorpius), the X-ray emission of Scorpius X-1 is 10,000 times greater than its visual emission, whereas that of the Sun is about a million times less. In addition, the energy output in X-rays is 100,000 times greater than the total emission of the Sun in all wavelengths.

Many thousands of X-ray sources have since been discovered. In addition, the space between galaxies in galaxy clusters is filled with a very hot, but very dilute gas at a temperature between 10 and 100 megakelvins (MK). The total amount of hot gas is five to ten times the total mass in the visible galaxies.

Visible nebula
Pre-stellar nebula
Stellar nebula
Post-stellar nebula
Clouds
Morphology
List-Class article Lists

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.