Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a

starburst galaxy A starburst galaxy is one 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 formatio ...

approximately 12 million

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distance, astronomical distances and is equivalent to about 9.46 Orders of magnitude (numbers)#1012, trillion kilometers (), or 5.88 ...

s away in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...

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) bear," referring to and contrasting it with nearby Ursa ...

. It is the second-largest member of the

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 ...

, with the D₂₅ isophotal diameter of . It is about five times more luminous than 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 eye. ...

and its central region is about one hundred times more luminous. The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As one of the closest starburst galaxies to Earth, M82 is the prototypical example of this galaxy type.

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 . The supernova was discovered by chance during an ...

, a

type Ia supernova A Type Ia supernova (read: "type one-A") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. The other star can be anything from a giant star to an even smaller white ...

, was discovered in the galaxy on 21 January 2014. In 2014, in studying M82, scientists discovered the brightest pulsar yet known, designated

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 sy ...

Discovery

M82, with M81, was discovered by

Johann Elert Bode Johann Elert Bode (; 19 January 1747 – 23 November 1826) was a German astronomer known for his reformulation and popularisation of the Titius–Bode law. Bode determined the orbit of Uranus and suggested the planet's name. Life and career ...

in 1774; he described it as a "nebulous patch", this one about degree away from the other, "very pale and of elongated shape". In 1779,

Pierre Méchain Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was born i ...

independently rediscovered both objects and reported them to

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose ...

, who added them to his catalog.

Structure

M82 was believed to be an irregular galaxy. In 2005, however, two symmetric

spiral arm Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...

(NIR) images of M82. The arms were detected by subtracting an

axisymmetric Rotational symmetry, also known as radial symmetry in geometry, is the property a shape has when it looks the same after some rotation by a partial turn. An object's degree of rotational symmetry is the number of distinct orientations in which i ...

exponential disk from the NIR images. Even though the arms were detected in NIR images, they are bluer than the disk. The arms had been missed due to M82's high disk

surface brightness In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on it ...

, the nearly edge-on view of this galaxy (~80°), and obscuration by a complex network of dusty filaments in its optical images. These arms emanate from the ends of the NIR

bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * 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.

Starburst region

In 2005, the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

revealed 197 young massive clusters in the starburst core. The average mass of these clusters is around 200,000 solar masses, hence the starburst core is a very energetic and high-density environment. Throughout the galaxy's center, young stars are being born 10 times faster than they are inside the entire

Milky Way Galaxy 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 eye. ...

. 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. These clumps correspond to known sources at

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

, and

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a tr ...

frequencies. Consequently, they are thought to be the least obscured starburst clusters from our vantage point. M82's unique bipolar outflow (or ' superwind') appears to be concentrated on clumps A and C, and is fueled by energy released by

supernovae A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

within the clumps which occur at a rate of about one every ten years. The

Chandra X-ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...

detected fluctuating

emissions about 600 light-years from the center of M82. Astronomers have postulated that this comes from the first known intermediate-mass black hole, of roughly 200 to 5000

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es. M82, like most galaxies, hosts a

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions of times the mass of the Sun (). Black holes are a class of astronomical ob ...

at its center. This one has mass of approximately 3 × 10⁷ solar masses, as measured from stellar dynamics.

Unknown object

In April 2010, radio astronomers working at the

Jodrell Bank Observatory Jodrell Bank Observatory () in Cheshire, England, hosts a number of radio telescopes as part of the Jodrell Bank Centre for Astrophysics at the University of Manchester. The observatory was established in 1945 by Bernard Lovell, a radio astro ...

of the

University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The university owns and operates majo ...

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. There have been several theories about the nature of this object, but currently no theory entirely fits the observed data. 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 SS 433 is one of the most exotic star systems observed. It is located in the Milky Way galaxy, and is an eclipsing X-ray binary system, with the primary being a stellar-mass black hole. The spectrum of the secondary companion star sugg ...

.Tana Joseph, Thomas Maccarone, Robert Fender:
The unusual radio transient in M82: an SS 433 analogue?
', 2011-07-25 However, all known microquasars produce large quantities of X-rays, whereas the object's X-ray flux is below the measurement threshold. 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 Faster-than-light (also FTL, superluminal or supercausal) travel and communication are the conjectural propagation of matter or information faster than the speed of light (). The special theory of relativity implies that only particles with z ...

motion of four times the speed of light relative to the galaxy center. Apparent superluminal motion is consistent with relativistic jets in massive black holes and does not indicate that the source itself is moving above lightspeed.

Starbursts

M82 is being physically affected by its larger neighbor, the

spiral In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:M81. Tidal forces caused by

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

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. The most recent such encounter is thought to have happened around 2–5 years ago and resulted in a concentrated starburst together with a corresponding marked peak in the cluster age distribution. This starburst ran for up to ~50 Myr at a rate of ~10 ''M''_⊙ per year. 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. 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 Halo, halos or haloes usually refer to: * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head HALO, halo, halos or haloes may also refer to: Arts and entertainment Video games * ''Halo'' (franch ...

. A suggestion to explain those features is that M82 was previously a

low surface brightness galaxy A low-surface-brightness galaxy, or LSB galaxy, is a diffuse galaxy with a surface brightness that, when viewed from Earth, is at least one magnitude lower than the ambient night sky. Most LSBs are dwarf galaxy, dwarf galaxies, and most of their ...

where star formation was triggered due to interactions with its giant neighbor. 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. The actual separation is .

Supernovae

As a starburst galaxy, Messier 82 is prone to frequent supernova, caused by the collapse of young, massive stars. The first (although false) supernova candidate reported was SN 1986D, initially believed to be a supernova inside the galaxy until it was found to be a variable short-wavelength infrared source instead. The first confirmed supernova recorded in the galaxy was SN 2004am, discovered in March 2004 from images taken in November 2003 by the

Lick Observatory The Lick Observatory is an astronomical observatory owned and operated by the University of California. It is on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, United States. The observatory is managed by t ...

Supernova Search. It was later determined to be a

Type II supernova A Type II supernova (plural: ''supernovae'' or ''supernovas'') results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, but no more than 40 to 50 times, the mass of the Sun () to undergo this ...

. In 2008, a radio transient was detected in the galaxy, designated SN 2008iz and thought to be a possible radio-only supernova, being too obscured in visible light by dust and gas clouds to be detectable. A similar radio-only transient was reported in 2009, although never received a formal designation and was similarly unconfirmed. Prior to accurate and thorough supernova surveys, many other supernovae likely occurred in previous decades. The

European VLBI Network The European VLBI Network (EVN) is a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa and Puerto Rico, which performs very high angular resolution observations of cosmic radio sources usin ...

studied a number of potential supernova remnants in the galaxy in the 1980s and 90s. One supernova remnant displayed clear expansion between 1986 and 1997 that suggested it originally went supernova in the early 1960s, and two other remnants show possible expansion that could indicate an age almost as young, but could not be confirmed at the time.

2014 supernova

On 21 January 2014 at 19.20 UT, a new distinct star was observed in M82, at apparent magnitude +11.7, by astrophysics lecturer

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 ...

and four of his students, at the

University of London Observatory UCL Observatory (called the University of London Observatory until 2015) at Mill Hill in London is an astronomical teaching observatory. It is part of the Department of Physics and Astronomy at University College London. History The Observator ...

. It had brightened to magnitude +10.9 two days later. Examination of earlier observations of M82 found the supernova to figure on the intervening day as well as on 15 through 20 January, brightening from magnitude +14.4 to +11.3; it could not be found, to limiting magnitude +17, from images caught of 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, but peaked at fainter +10.5 on the last day of the month. Preliminary analysis classified it as "a young, reddened

". The International Astronomical Union (IAU) has designated it SN 2014J.

SN 1993J SN 1993J is a supernova observed in the galaxy M81. It was discovered on 28 March 1993 by F. Garcia in Spain. At the time, it was the second-brightest type II supernova observed in the twentieth century behind SN 1987A, peaking at a visible ap ...

was also at relatively close distance, in M82's larger companion galaxy M81.

SN 1987A SN 1987A was a type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately from Earth and was the closest observed supernova since Kepler's Supernova. 1987A's light reached Earth on ...

in the

Large Magellanic Cloud The Large Magellanic Cloud (LMC), or Nubecula Major, is a satellite galaxy of the Milky Way. At a distance of around 50 kiloparsecs (≈160,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the ...

was much closer. 2014J is the closest type Ia supernova since

SN 1972E SN1972E was a supernova in the galaxy NGC 5253 that was discovered 13 May 1972 with an apparent B magnitude of about 8.5, shortly after it had reached its maximum brightness. In terms of apparent brightness, it was the second-brightest supernova ...

Notes

References

External links

M82, SEDS Messier pages

M82 at Chandra

SST: Galaxy on Fire!

M82 at NASA/IPAC EXTRAGALACTIC DATABASEESA/Hubble images of M82
*

* ttp://deepspacemap.com/#?l=69.6772,31.037,11 M82 at Deep Space Map {{DEFAULTSORT:Messier 082 Starburst galaxies Irregular galaxies M81 Group Ursa Major (constellation) 082 NGC objects 05322 28655 337

231 Year 231 ( CCXXXI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. At the time, it was known as the Year of the Consulship of Claudius and Sallustus (or, less frequently, year 984 ''Ab urbe c ...

Discoveries by Johann Elert Bode Astronomical objects discovered in 1774