Messier 82

Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa Major. A member of the M81 Group, it is about five times more luminous than the whole Milky Way and has a center one hundred times more luminous than our galaxy's center.[7] The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As the closest starburst galaxy to Earth, M82 is the prototypical example of this galaxy type.[7] SN 2014J, a type Ia supernova, was discovered in the galaxy on 21 January 2014.[8][9][10] In 2014, in studying M82, scientists discovered the brightest pulsar yet known, designated M82 X-2.[11][12][13]

Messier 82
M82 HST ACS 2006-14-a-large web
A mosaic image taken by the Hubble Telescope of Messier 82, combining exposures taken with four colored filters that capture starlight from visible and infrared wavelengths as well as the light from the glowing hydrogen filaments.
Observation data (J2000 epoch)
ConstellationUrsa Major
Right ascension 09h 55m 52.2s[1]
Declination+69° 40′ 47″[1]
Redshift203±4 km/s[1]
Distance11.4-12.4 Mly (3.5-3.8 Mpc)[2]
Apparent magnitude (V)8.41[3][4]
Characteristics
TypeI0[1]
Size~37,000ly in diameter[5]
Apparent size (V)11′.2 × 4′.3[1]
Notable featuresEdge on starburst galaxy
Other designations
NGC 3034, UGC 5322, Arp 337, Cigar Galaxy, PGC 28655, 3C 231[1]
PIA23010-M82-CigarGalaxy-20190305
M82 galaxy (5 March 2019)
M82 Chandra HST Spitzer
Composite image – HST (vis); Spitzer (ir); Chandra (x-ray).
M82(2)
Chandra X-ray observatory image of the galaxy.
Hubble views new supernova in Messier 82
Hubble views new supernova in Messier 82[6]
M 82 supernova
M82 – Dec 2013; supernova – Jan 2014 (bottom)

Discovery

M82 was first discovered by Johann Elert Bode on December 31, 1774 together with M81; he described it as a "nebulous patch", about 0.75 deg away from M81, "very pale and of elongated shape". In 1779, Pierre Méchain independently rediscovered both galaxies and reported them to Charles Messier, who added them to his catalog.[14]

Structure

M82 was previously believed to be an irregular galaxy. In 2005, however, two symmetric spiral arms were discovered in near-infrared (NIR) images of M82. The arms were detected by subtracting an axisymmetric exponential disk from the NIR images. Even though the arms were detected in NIR images, they are bluer than the disk. The arms were previously missed due to M82's high disk surface brightness, the nearly edge-on view of this galaxy (~80°),[7] and obscuration by a complex network of dusty filaments in its optical images. These arms emanate from the ends of the NIR bar and can be followed for the length of 3 disc scales. Assuming that the northern part of M82 is nearer to us, as most of the literature does, the observed sense of rotation implies trailing arms.[15]

Starburst region

In 2005, the Hubble Space Telescope revealed 197 young massive clusters in the starburst core.[7] The average mass of these clusters is around 200,000 solar masses, hence the starburst core is a very energetic and high-density environment.[7] Throughout the galaxy's center, young stars are being born 10 times faster than they are inside the entire Milky Way Galaxy.[16]

In the core of M82, the active starburst region spans a diameter of 500 pc. Four high surface brightness regions or clumps (designated A, C, D, and E) are detectable in this region at visible wavelengths.[7] These clumps correspond to known sources at X-ray, infrared, and radio frequencies.[7] Consequently, they are thought to be the least obscured starburst clusters from our vantage point.[7] M82's unique bipolar outflow (or 'superwind') appears to be concentrated on clumps A and C and is fueled by energy released by supernovae within the clumps which occur at a rate of about one every ten years.[7]

The Chandra X-ray Observatory detected fluctuating X-ray emissions from a location approximately 600 light-years away from the center of M82. Astronomers have postulated that this fluctuating emission comes from the first known intermediate-mass black hole, of roughly 200 to 5000 solar masses.[17] M82, like most galaxies, hosts a supermassive black hole at its center with a mass of approximately 3 x 107 solar masses as measured from stellar dynamics.[18]

Unknown object

In April 2010, radio astronomers working at the Jodrell Bank Observatory of the University of Manchester in the UK reported an object in M82 that had started sending out radio waves, and whose emission did not look like anything seen anywhere in the universe before.[19]

There have been several theories about the nature of this object, but currently no theory entirely fits the observed data.[19] It has been suggested that the object could be an unusual "micro quasar", having very high radio luminosity yet low X-ray luminosity, and being fairly stable, it could be an analogue of the low X-ray luminosity galactic microquasar SS 433.[20] However, all known microquasars produce large quantities of X-rays, whereas the object's X-ray flux is below the measurement threshold.[19] The object is located at several arcseconds from the center of M82 which makes it unlikely to be associated with a supermassive black hole. It has an apparent superluminal motion of four times the speed of light relative to the galaxy center.[21][22] Apparent superluminal motion is consistent with relativistic jets in massive black holes and does not indicate that the source itself is moving above lightspeed.[21]

Starbursts

M82 is being physically affected by its larger neighbor, the spiral M81. Tidal forces caused by gravity have deformed M82, a process that started about 100 million years ago. This interaction has caused star formation to increase tenfold compared to "normal" galaxies.

M82 has undergone at least one tidal encounter with M81 resulting in a large amount of gas being funneled into the galaxy's core over the last 200 Myr.[7] The most recent such encounter is thought to have happened around 2–5×108 years ago and resulted in a concentrated starburst together with a corresponding marked peak in the cluster age distribution.[7] This starburst ran for up to ~50 Myr at a rate of ~10 M per year.[7] Two subsequent starbursts followed, the last (~4–6 Myr ago) of which may have formed the core clusters, both super star clusters (SSCs) and their lighter counterparts.[7]

Stars in M82's disk seem to have been formed in a burst 500 million years ago, leaving its disk littered with hundreds of clusters with properties similar to globular clusters (but younger), and stopped 100 million years ago with no star formation taking place in this galaxy outside the central starburst and, at low levels since 1 billion years ago, on its halo. A suggestion to explain those features is that M82 was previously a low surface brightness galaxy where star formation was triggered due to interactions with its giant neighbor.[23]

Ignoring any difference in their respective distances from the Earth, the centers of M81 and M82 are visually separated by about 130,000 light-years.[24] The actual separation is 300+300
−200
 kly
.[25][2]

2014 supernova

On 21 January 2014 at 19.20 UT, a previously unseen star was observed in M82 at magnitude +11.7 by Dr. Steve J. Fossey, along with a team of 4 of his students, at University College London's training observatory, the University of London Observatory. It had brightened to magnitude +10.9 by 23 January. Examination of earlier observations of M82 found the supernova to be present on 15, 16, 17, 19, 20 and 22 January, brightening from magnitude +14.4 to +11.3; there was no sign of it, to limiting magnitude +17, on 14 January. It was initially suggested that it could become as bright as magnitude +8.5, well within the visual range of small telescopes and large binoculars,[26] but it actually peaked at a rather fainter +10.5 on 31 January 2014.[27] Preliminary analysis classified it as "a young, reddened type Ia supernova". The International Astronomical Union (IAU) has designated it SN 2014J.[28] SN 2014J is one of the closest supernovae to Earth observed in recent decades. SN 1993J was at a very similar distance, in M82's larger companion galaxy M81, and SN 1987A in the Large Magellanic Cloud was much closer. 2014J is the closest type Ia supernova since SN 1972E. [8][9][10]

See also

  • Baby Boom Galaxy – The brightest starburst galaxy in the very distant universe

References

  1. ^ a b c d e f "NASA/IPAC Extragalactic Database". Results for NGC 3034. Retrieved 27 October 2006.
  2. ^ a b Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6.
  3. ^ "M 82". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 14 December 2018.
  4. ^ Armando, Gil de Paz; Boissier; Madore; Seibert; Boselli; et al. (2007). "The GALEX Ultraviolet Atlas of Nearby Galaxies". Astrophysical Journal Supplement. 173 (2): 185–255. arXiv:astro-ph/0606440. Bibcode:2007ApJS..173..185G. doi:10.1086/516636.
  5. ^ "M82 - Cigar Galaxy". astropixels.com. 26 March 2012. Retrieved 15 December 2018.
  6. ^ "Hubble views new supernova in Messier 82". ESA / HUBBLE. Retrieved 12 March 2014.
  7. ^ a b c d e f g h i j k l m Barker, S.; de Grijs, R.; Cerviño, M. (2008). "Star cluster versus field star formation in the nucleus of the prototype starburst galaxy M 82". Astronomy and Astrophysics. 484 (3): 711–720. arXiv:0804.1913. Bibcode:2008A&A...484..711B. doi:10.1051/0004-6361:200809653.
  8. ^ a b "ATel #5786: Classification of Supernova in M82 as a young, reddened Type Ia Supernova". ATel. Retrieved 14 April 2018.
  9. ^ a b "Sudden Supernova In M82 Galaxy Rips Apart The Night Sky (A Bit)". Huffington Post.
  10. ^ a b Plait, Phil (22 January 2014). "KABOOM! Nearby Galaxy M82 Hosts a New Supernova!". Retrieved 14 April 2018 – via Slate.
  11. ^ "Shockingly Bright Dead Star with a Pulse Is an X-ray Powerhouse". Space.com. 8 October 2014.
  12. ^ "Researchers detect brightest pulsar ever recorded". Massachusetts Institute of Technology. 8 October 2014.
  13. ^ "NASA's NuSTAR Telescope Discovers Shockingly Bright Dead Star". NASA. 8 October 2014.
  14. ^ "Messier 82". SEDS.
  15. ^ Mayya, Y. D.; Carrasco, L.; Luna, A. (2005). "The Discovery of Spiral Arms in the Starburst Galaxy M82". Astrophysical Journal. 628 (1): L33–L36. arXiv:astro-ph/0506275. Bibcode:2005ApJ...628L..33M. doi:10.1086/432644.
  16. ^ Happy Sweet Sixteen, Hubble Telescope! Newswise, Retrieved 30 July 2008.
  17. ^ Patruno, A.; Portegies Zwart, S.; Dewi, J.; Hopman, C. (2006). "The ultraluminous X-ray source in M82: an intermediate-mass black hole with a giant companion". Monthly Notices of the Royal Astronomical Society: Letters. 370 (1): L6–L9. arXiv:astro-ph/0602230. Bibcode:2006MNRAS.370L...6P. doi:10.1111/j.1745-3933.2006.00176.x.
  18. ^ Gaffney, N. I.; Lester, D. F. & Telesco, C. M. (1993). "The stellar velocity dispersion in the nucleus of M82". Astrophysical Journal Letters. 407: L57–L60. Bibcode:1993ApJ...407L..57G. doi:10.1086/186805.
  19. ^ a b c "Mysterious radio waves emitted from nearby galaxy". Retrieved 14 April 2018.
  20. ^ Tana Joseph, Thomas Maccarone, Robert Fender: The unusual radio transient in M82: an SS 433 analogue?, 2011-07-25
  21. ^ a b Muxlow, T. W. B.; Beswick, R. J.; Garrington, S. T.; Pedlar, A.; Fenech, D. M.; Argo, M. K.; Van Eymeren, J.; Ward, M.; Zezas, A.; Brunthaler, A.; Rich, R. M.; Barlow, T. A.; Conrow, T.; Forster, K.; Friedman, P. G.; Martin, D. C.; Morrissey, P.; Neff, S. G.; Schiminovich, D.; Small, T.; Donas, J.; Heckman, T. M.; Lee, Y. -W.; Milliard, B.; Szalay, A. S.; Yi, S. (2010). "Discovery of an unusual new radio source in the star-forming galaxy M82: Faint supernova, supermassive black hole or an extragalactic microquasar?". Monthly Notices of the Royal Astronomical Society: Letters. 404 (1): L109–L113. arXiv:1003.0994v1. Bibcode:2010MNRAS.404L.109M. doi:10.1111/j.1745-3933.2010.00845.x.
  22. ^ O'Brien, Tim. "Mystery object in Starburst Galaxy M82 - Jodrell Bank Centre for Astrophysics". www.jb.man.ac.uk. Retrieved 14 April 2018.
  23. ^ Divakara Mayya, Y.; Carrasco, Luis (2009). "M82 as a Galaxy: Morphology and Stellar Content of the Disk and Halo". Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias. 37: 44–55. arXiv:0906.0757. Bibcode:2009arXiv0906.0757D.
  24. ^ Declination separation of 36′.87 and Right Ascension separation of 9′.5 gives via Pythagorean theorem a visual separation of 38′.07; Average distance of 11.65 Mly × sin(38′.07) = 130,000 ly visual separation.
  25. ^ Separation = sqrt(DM812 + DM822 – 2 DM81 DM82 Cos(38′.07)) assuming the error direction is about the same for both objects.
  26. ^ "Astronomy Now: Bright, young supernova outburst in Messier 82, MARK ARMSTRONG, 23 January 2014". Retrieved 14 April 2018.
  27. ^ "Supernova in M82 Passes Its Peak - Sky & Telescope". 17 February 2014. Retrieved 14 April 2018.
  28. ^ "Supernova in Messier 82 discovered by UCL students". www.ucl.ac.uk. Retrieved 14 April 2018.

External links

Coordinates: Sky map 09h 55m 52.2s, +69° 40′ 47″

82 (number)

82 (eighty-two) is the natural number following 81 and preceding 83.

Baby Boom Galaxy

The Baby Boom Galaxy is a starburst galaxy located 12.2 billion light years away. Discovered by NASA's Spitzer Science Center at the California Institute of Technology, the galaxy is the record holder for the brightest starburst galaxy in the very distant universe, with brightness being a measure of its extreme star-formation rate. The Baby Boom Galaxy has been nicknamed "the extreme stellar machine" because it is seen producing stars at a rate of up to 4,000 per year (one star every 2.2 hours). The Milky Way galaxy in which Earth resides turns out an average of just 10 stars per year.

Cigar (disambiguation)

A cigar is a roll of tobacco.

List of black holes

This is a list of black holes (and stars considered probable candidates) organized by size (including black holes of undetermined mass); some items in this list are galaxies or star clusters that are believed to be organized around a black hole. Messier and New General Catalogue designations are given where possible.

List of novae in 2018

The following is a list of all novae that are known to have occurred in 2018. A nova is an energetic astronomical event caused by a white dwarf accreting matter from a star it is orbiting (typically a red giant, whose outer layers are more weakly attached than smaller, denser stars) Alternatively, novae can rarely be caused by a pair of stars merging with each other, however such events are vastly less common than novae caused by white dwarves.

In 2018, 15 novae were discovered in the Milky Way, 14 being classical novae, and 1 being a dwarf nova of a previously known variable star, V392 Persei, which was discovered in 1972. An additional 23 novae were discovered in the Andromeda Galaxy, 8 in Messier 81, 1 in the Triangulum Galaxy, and 1 in Messier 83.

M81 Group

The M81 Group is a galaxy group in the constellations Ursa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the Local Group. The group is estimated to have a total mass of (1.03 ± 0.17)×1012M☉.

The M81 Group, the Local Group, and other nearby groups all lie within the Virgo Supercluster (i.e. the Local Supercluster).

M82 X-2

M82 X-2 is an X-ray pulsar located in the galaxy Messier 82, approximately 12 million light-years from Earth. It is exceptionally luminous, radiating energy equivalent to approximately ten million Suns. This object is part of a binary system: If the pulsar is of an average size, 1.4 M☉, then its companion is at least 5.2 M☉. On average, the pulsar rotates every 1.37 seconds, and revolves around its more massive companion every 2.5 days.M82 X-2 is an ultraluminous X-ray source (ULX), shining about 100 times brighter than theory suggests something of its mass should be able to. Its brightness is many times higher than the Eddington limit, a basic physics guideline that sets an upper limit on the brightness that an object of a given mass should be able to achieve. Possible explanations for violations of the Eddington limit include geometrical effects arising from the funneling of in-falling material along magnetic field lines.

While M82 X-2 was previously known as an X-ray source, it was not until an observation campaign to study the newly discovered supernova SN 2014J in January 2014 that X-2's true nature was uncovered. Scientists looking at data from the NuSTAR spacecraft noticed a pulsing in the X-ray spectrum coming from near the supernova in Messier 82. Data from the Chandra and Swift spacecraft was used to verify the NuSTAR findings and provide the necessary spatial resolution to determine the exact source. After combining the NuSTAR and Chandra data, scientists were able to discern that M82 X-2 emitted both an X-ray beam and continuous broad X-ray radiation.

Messier 81

Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away, with a diameter of 90,000 light years, about half the size of the Milky Way, in the constellation Ursa Major. Due to its proximity to Earth, large size, and active galactic nucleus (which harbors a 70 million M☉supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also makes it a popular target for amateur astronomers.Messier 81 was first discovered by Johann Elert Bode on December 31, 1774. Consequently, the galaxy is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, which was subsequently listed in the Messier Catalogue.

Messier 81 is located approximately 10° northwest of Alpha Ursae Majoris along with several other galaxies in the Messier 81 Group.Messier 81 and Messier 82 can both be viewed easily using binoculars and small telescopes. The two objects are generally not observable to the unaided eye, although highly experienced amateur astronomers may be able to see Messier 81 under exceptional observing conditions with a very dark sky. Telescopes with apertures of 8 inches (20 cm) or larger are needed to distinguish structures in the galaxy. Its far northern declination makes it generally visible for observers in the northern hemisphere. It is not visible to most observers in the southern hemisphere, except those in a narrow latitude range immediately south of the equator.

Most of the emission at infrared wavelengths originates from interstellar dust. This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation regions. The general explanation is that the hot, short-lived blue stars that are found within star formation regions are very effective at heating the dust and thus enhancing the infrared dust emission from these regions.

Only one supernova has been detected in Messier 81. The supernova, named SN 1993J, was discovered on 28 March 1993 by F. García in Spain. At the time, it was the second brightest supernova observed in the 20th century. The spectral characteristics of the supernova changed over time. Initially, it looked more like a type II supernova (a supernova formed by the explosion of a giant star) with strong hydrogen spectral line emission, but later the hydrogen lines faded and strong helium spectral lines appeared, making the supernova look more like a type Ib.Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernova, but did resemble the variations observed in type Ib supernovae. Hence, the supernova has been classified as a type IIb, a transitory class between type II and type Ib. The scientific results from this supernova suggested that type Ib and Ic supernovae were formed through the explosions of giant stars through processes similar to those taking place in type II supernovae. The supernova was also used to estimate a distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Messier 81. As a local galaxy, the Central Bureau for Astronomical Telegrams (CBAT) tracks novae in M81 along with M31 and M33.

Messier 81 is the largest galaxy in the M81 Group, a group of 34 galaxies located in the constellation Ursa Major. At approximately 11.7 Mly (3.6 Mpc) from the Earth, it makes this group and the Local Group, containing the Milky Way, relative neighbors in the Virgo Supercluster.

Gravitational interactions of M81 with M82 and NGC 3077 have stripped hydrogen gas away from all three galaxies, forming gaseous filamentary structures in the group. Moreover, these interactions have allowed interstellar gas to fall into the centers of M82 and NGC 3077, leading to vigorous star formation or starburst activity there.

Messier object

The Messier objects are a set of 110 astronomical objects cataloged by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles ("Catalogue of Nebulae and Star Clusters").

Because Messier was interested in finding only comets, he created a list of non-comet objects that frustrated his hunt for them. The compilation of this list, in collaboration with his assistant Pierre Méchain, is known as the Messier catalogue. This catalogue of objects is one of the most famous lists of astronomical objects, and many Messier objects are still referenced by their Messier number.

The catalogue includes some astronomical objects that can be observed from Earth's Northern Hemisphere such as deep-sky objects, a characteristic which makes the Messier objects extremely popular targets for amateur astronomers.A preliminary version first appeared in the Memoirs of the French Academy of Sciences in 1771,

and the last item was added in 1966 by Kenneth Glyn Jones, based on Messier's observations.

The first version of Messier's catalogue contained 45 objects and was published in 1774 in the journal of the French Academy of Sciences in Paris. In addition to his own discoveries, this version included objects previously observed by other astronomers, with only 17 of the 45 objects being Messier's.

By 1780 the catalogue had increased to 80 objects. The final version of the catalogue containing 103 objects was published in 1781 in the Connaissance des Temps for the year 1784.

However, due to what was thought for a long time to be the incorrect addition of Messier 102, the total number remained 102. Other astronomers, using side notes in Messier's texts, eventually filled out the list up to 110 objects.The catalogue consists of a diverse range of astronomical objects, ranging from star clusters and nebulae to galaxies. For example, Messier 1 is a supernova remnant, known as the Crab Nebula, and the great spiral Andromeda Galaxy is M31. Many further inclusions followed in the next century when the first addition came from Nicolas Camille Flammarion in 1921, who added Messier 104 after finding Messier's side note in his 1781 edition exemplar of the catalogue. M105 to M107 were added by Helen Sawyer Hogg in 1947, M108 and M109 by Owen Gingerich in 1960, and M110 by Kenneth Glyn Jones in 1967.

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.

NGC 4236

NGC 4236 (also known as Caldwell 3) is a barred spiral galaxy located in the constellation Draco.

The galaxy is a member of the M81 Group, a group of galaxies located at a distance of approximately 11.7 Mly (3.6 Mpc) from Earth. The group also contains the spiral galaxy Messier 81 and the starburst galaxy Messier 82. NGC 4236 is located away from the central part of the M81 group at a distance of is 14.5 Mly (4.45 Mpc) from Earth.

NGC 6045

NGC 6045 is a barred spiral galaxy located about 450 million light-years away in the constellation Hercules. NGC 6045 was discovered by astronomer Lewis Swift on June 27, 1886 and is a member of the Hercules Cluster. It is also a LINER galaxy.

SN 2014J

SN 2014J was a type-Ia supernova in Messier 82 (the 'Cigar Galaxy', M82) discovered in mid-January 2014. It was the closest type-Ia supernova discovered for 42 years, and none have been closer as of 2018. The supernova was discovered by chance during an undergraduate teaching session at the University of London Observatory. It peaked on 31 January 2014, reaching an apparent magnitude of 10.5. SN 2014J was the subject of an intense observing campaign by professional astronomers and was bright enough to be seen by amateur astronomers.

Sculptor Galaxy

The Sculptor Galaxy, also known as the Silver Coin or Silver Dollar Galaxy, NGC 253, is an intermediate spiral galaxy in the constellation Sculptor. The Sculptor Galaxy is a starburst galaxy, which means that it is currently undergoing a period of intense star formation.

Starburst galaxy

A starburst galaxy is a galaxy undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy or the star formation rate observed in most other galaxies. For example, the star formation rate of the Milky Way galaxy is approximately 3 M☉/yr, however, starburst galaxies can experience star formation rates that are more than a factor of 100 times greater. In a starburst galaxy, the rate of star formation is so large that the galaxy will consume all of its gas reservoir, from which the stars are forming, on a timescale much shorter than the age of the galaxy. As such, the starburst nature of a galaxy is a phase, and one that typically occupies a brief period of a galaxy's evolution. The majority of starburst galaxies are in the midst of a merger or close encounter with another galaxy. Starburst galaxies include M82, NGC 4038/NGC 4039 (the Antennae Galaxies), and IC 10.

Starburst region

A starburst is an astrophysical process that involves star formation occurring at a rate that is large compared to the rate that is typically observed. This starburst activity will consume the available interstellar gas supply over a timespan that is much shorter than the lifetime of the galaxy. For example, the nebula NGC 6334 has a star formation rate estimated to be 3600 Solar Masses per million years compared the star formation rate of the entire Milky Way of about seven million solar masses per million years. Due to the high amount of star formation a starburst is usually accompanied by much higher gas pressure and a larger ratio of Hydrogen cyanide to Carbon monoxide Emission-lines than are usually observed.

Starburst can occur in entire galaxies or just regions of space. A starburst region is a region of space that is undergoing a large amount of star formation. For example, the Tarantula Nebula is a Nebula in the Large Magellanic Cloud which has one of the highest star formation rates in the Local Group. By contrast a starburst galaxy is an entire galaxy that is experiencing a very high star formation rate. One notable example being Messier 82 in which the gas pressure is 100 times greater than in the local neighborhood and it is forming stars at about the same rate as the Milky Way in a region about 600 parsecs across. At this rate M82 will consume its 200 million Solar Masses of atomic and molecular hydrogen in 100 Mega years (its Free-fall time).Starburst regions can occur in different shapes, for example in Messier 94 the inner ring is a star burst region. Messier 82 has a starburst core of about 600 parsec in diameter. Starbursts are common during galaxy mergers such as the Antennae Galaxies. In the case of mergers the starburst can either be local or galaxy wide depending on the galaxies and how they are merging.

Steve Fossey

Stephen John Fossey is a British astronomer working at UCL Observatory, which is part of University College London (UCL). He is one of the three editors of The Observatory magazine.Fossey's research interests are in the interstellar medium, exoplanets and time-domain astronomy. He co-discovered the transit of the (previously-known) exoplanet HD 80606b (along with Ingo Waldmann and David Kipping) in 2009. Fossey also discovered supernova SN 2014J, the closest supernova for each for several decades, in January 2014.

Ursa Major

Ursa Major (; also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) she-bear," referring to and contrasting it with nearby Ursa Minor, the lesser bear. In antiquity, it was one of the original 48 constellations listed by Ptolemy in the 2nd century AD. Today it is the third largest of the 88 modern constellations.

Ursa Major is primarily known from the asterism of its main seven stars, which has been called the "Big Dipper," "the Wagon," "Charles's Wain," and "the Plough," among other names. In particular, the Big Dipper's stellar configuration mimics the shape of the "Little Dipper." Its two brightest stars, named Dubhe and Merak (α Ursae Majoris and β Ursae Majoris), can be used as the navigational pointer towards the place of the current northern pole star, Polaris in Ursa Minor.

Ursa Major, along with asterisms that incorporate or comprise it, is significant to numerous world cultures, often as a symbol of the north. Its depiction on the flag of Alaska is a modern example of such symbolism.

Ursa Major is visible throughout the year from most of the northern hemisphere, and appears circumpolar above the mid-northern latitudes. From southern temperate latitudes, the main asterism is invisible, but the southern parts of the constellation can still be viewed.

List
See also

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