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Mensa is a
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
in the
Southern Celestial Hemisphere The southern celestial hemisphere, also called the Southern Sky, is the Southern Hemisphere, southern half of the celestial sphere; that is, it lies south of the celestial equator. This arbitrary sphere, on which seemingly fixed stars form cons ...
near the south
celestial pole The north and south celestial poles are the two points in the sky where Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers at ...
, one of fourteen constellations drawn up in the 18th century by French astronomer
Nicolas-Louis de Lacaille Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a kingdom of France, French astronomer and geodesist who named 14 out of the IAU designated constellations, 88 constellations. From 1750 ...
. Its name is Latin for table, though it originally commemorated
Table Mountain Table Mountain (; ) is a flat-topped mountain forming a prominent landmark overlooking the city of Cape Town in South Africa. It is a significant tourist attraction, with many visitors using the Table Mountain Aerial Cableway, cableway or hik ...
and was known as "Mons Mensae". One of the eighty-eight constellations designated by the
International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
(IAU), it covers a keystone-shaped wedge of sky 153.5
square degree __NOTOC__ A square degree (deg2) is a non- SI unit measure of solid angle. Other denotations include ''sq. deg.'' and (°)2. Just as degrees are used to measure parts of a circle, square degrees are used to measure parts of a sphere. Analogous ...
s in area. Other than the south polar constellation of
Octans Octans is a faint constellation located in the deep southern celestial hemisphere, Southern Sky. Its name is Latin for the eighth part of a circle, but it is named after the octant (instrument), octant, a navigational instrument. Devised by kingd ...
, it is the most southerly of constellations and is observable only south of the 5th parallel of the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar ...
. One of the faintest constellations in the night sky, Mensa contains no apparently bright stars—the brightest, Alpha Mensae, is barely visible in suburban skies. Part of the
Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around , the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal Galaxy, Sagittarius Dwarf ...
, several
star clusters A star cluster is a group of stars held together by self-gravitation. Two main types of star clusters can be distinguished: globular clusters, tight groups of ten thousand to millions of old stars which are gravitationally bound; and open cluste ...
and a
quasar A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...
lie in the area covered by the constellation, and at least three of its star systems have been found to have
exoplanets An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detec ...
.


History

Originally named "Montagne de la Table" or "Mons Mensae", Mensa was created by
Nicolas-Louis de Lacaille Abbé Nicolas-Louis de Lacaille (; 15 March 171321 March 1762), formerly sometimes spelled de la Caille, was a kingdom of France, French astronomer and geodesist who named 14 out of the IAU designated constellations, 88 constellations. From 1750 ...
out of dim Southern Hemisphere stars in honor of
Table Mountain Table Mountain (; ) is a flat-topped mountain forming a prominent landmark overlooking the city of Cape Town in South Africa. It is a significant tourist attraction, with many visitors using the Table Mountain Aerial Cableway, cableway or hik ...
, a South African mountain overlooking
Cape Town Cape Town is the legislature, legislative capital city, capital of South Africa. It is the country's oldest city and the seat of the Parliament of South Africa. Cape Town is the country's List of municipalities in South Africa, second-largest ...
, near the location of Lacaille's observatory. He recalled that the
Magellanic Clouds The Magellanic Clouds (''Magellanic system'' or ''Nubeculae Magellani'') are two irregular dwarf galaxies in the southern celestial hemisphere. Orbiting the Milky Way galaxy, these satellite galaxies are members of the Local Group. Because both ...
were sometimes known as Cape clouds, and that Table Mountain was often covered in clouds when a southeasterly stormy wind blew. Hence he made a "table" in the sky under the clouds. Lacaille had observed and catalogued 10,000 southern stars during a two-year stay at the
Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...
. He devised 14 new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. Mensa was the only constellation that did not honor an instrument symbolic of the
Age of Enlightenment The Age of Enlightenment (also the Age of Reason and the Enlightenment) was a Europe, European Intellect, intellectual and Philosophy, philosophical movement active from the late 17th to early 19th century. Chiefly valuing knowledge gained th ...
. Sir
John Herschel Sir John Frederick William Herschel, 1st Baronet (; 7 March 1792 – 11 May 1871) was an English polymath active as a mathematician, astronomer, chemist, inventor and experimental photographer who invented the blueprint and did botanical work. ...
proposed shrinking the name to one word in 1844, noting that Lacaille himself had abbreviated some of his constellations thus. Although the stars of Mensa do not feature in any ancient mythology, the mountain it is named after has a rich mythology. Called "Tafelberg" in Dutch and German, it has two neighboring mountains called "Devil's Peak" and "Lion's Head". Table Mountain features in the mythology of the
Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...
, notorious for its storms. Explorer
Bartolomeu Dias Bartolomeu Dias ( – 29 May 1500) was a Portuguese mariner and explorer. In 1488, he became the first European navigator to round the Cape Agulhas, southern tip of Africa and to demonstrate that the most effective southward route for ships lies ...
saw the mountain as a mythical anvil for storms.


Characteristics

Mensa is bordered by
Dorado Dorado (, ) 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 mahi-mahi (''Coryphaena hippurus''), which is known as ''dorado'' ("golden") in Sp ...
to the north,
Hydrus Hydrus is a small constellation in the deep Southern Celestial Hemisphere, southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first ap ...
to the northwest and west, Octans to the south,
Chamaeleon Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius f ...
to the east and
Volans Volans is a constellation in the southern sky. It represents a flying fish; its name is a shortened form of its original name, Piscis Volans. Volans was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirks ...
to the northeast. Covering 153.5 square degrees and 0.372% of the night sky, it ranks 75th of the 88 constellations in size. The three-letter abbreviation for the constellation, as adopted by the IAU in 1922, is "Men". The official constellation boundaries, as set by Belgian astronomer
Eugène Delporte Eugene is a common male given name that comes from the Greek εὐγενής (''eugenēs''), "noble", literally "well-born", from εὖ (''eu''), "well" and γένος (''genos''), "race, stock, kin".equatorial coordinate system The equatorial coordinate system is a celestial coordinate system widely used to specify the positions of astronomical object, celestial objects. It may be implemented in spherical coordinate system, spherical or Cartesian coordinate system, rect ...
, the
right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...
coordinates of these borders lie between and , while the
declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...
coordinates are between −69.75° and −85.26°. The whole constellation is visible to observers south of latitude 5°N.


Features


Stars


Bright stars

Lacaille gave eleven stars in the constellation
Bayer designation A Bayer designation is a stellar designation in which a specific star is identified by a Greek alphabet, Greek or Latin letter followed by the genitive case, genitive form of its parent constellation's Latin name. The original list of Bayer design ...
s, using the
Greek alphabet The Greek alphabet has been used to write the Greek language since the late 9th or early 8th century BC. It was derived from the earlier Phoenician alphabet, and is the earliest known alphabetic script to systematically write vowels as wel ...
to label them Alpha through to Lambda Mensae (excluding Kappa).
Gould Gould may refer to: People * Gould (name), a surname Places United States * Gould, Arkansas, a city * Gould, Colorado, an unincorporated community * Gould, Ohio, an unincorporated community * Gould, Oklahoma, a town * Gould, West Virginia, an ...
later added Kappa, Mu, Nu, Xi and Pi Mensae. Stars as dim as these were not generally given designations; however, Gould felt their closeness to the South Celestial Pole warranted their naming. Alpha Mensae is the brightest star with a barely visible
apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
of 5.09, making it the only constellation with no star above magnitude 5.0. Overall, there are 22 stars within the constellation's borders brighter than or equal to
apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
6.5. * Alpha Mensae is a solar-type star (
class Class, Classes, or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used d ...
G7V) 33.32 ± 0.02
light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s from Earth. Enter the star name in the identifier bo
here
take reciprocal of parallax (in mas) and multiply by 3260 to get distance in light-years
It came to within 11 light-years from Earth around 250,000 years ago and would have been considerably brighter back then—nearly of second magnitude. An
infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are of ...
has been detected around this star, indicating the presence of a
circumstellar disk A Circumstellar disc (or circumstellar disk) is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the res ...
at a radius of over 147 
astronomical unit The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...
s (AU). The estimated temperature of this dust is below 22 K. Search for HIPPARCOS no. of the star: 29271 However, data from
Herschel Space Observatory The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telesco ...
failed to confirm this excess, leaving the finding in doubt. No planetary companions have yet been discovered around it. It has a
red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
companion star at an
angular separation Angular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors in three-dimensional space, or the central angle subtended by the radii through two points on a sphere. When t ...
of 3.05 
arcseconds A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
; equivalent to a
projected separation This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outs ...
of roughly 30 AU. (details on the stellar properties of the companion star) * Gamma Mensae is the second-brightest star in the constellation, at magnitude 5.19. Located 104.9 ± 0.5 light-years from Earth, it is an ageing (10.6 billion year-old) star around 1.04 times as massive as the Sun. It has swollen to around 5 times the
solar radius Solar radius is a unit of distance used to express the size of objects in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: 1\,R_ = 6.957 ...
, becoming an orange giant of spectral type K2III. * Beta Mensae is slightly fainter at magnitude 5.31. Located 660 ± 10 light-years from Earth, it is a yellow giant of spectral type G8III, around 3.6 times as massive and 513 times as luminous as the Sun. It is 270 million years old, and lies in front of the Large Magellanic Cloud. *
Zeta Zeta (, ; uppercase Ζ, lowercase ζ; , , classical or ''zē̂ta''; ''zíta'') is the sixth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 7. It was derived from the Phoenician alphabet, Phoenician letter zay ...
and Eta Mensae have infrared excesses suggesting they too have circumstellar disks of dust. Zeta Mensae is an ageing white giant of spectral type A5 III around 394 ± 4 light-years from Earth, and Eta Mensae is an orange giant of spectral type K4 III, lying 650 ± 10 light-years away from Earth. * Pi Mensae is a solar-type (G1) star 59.62 ± 0.07 light-years distant. In 2001, a
substellar A substellar object, sometimes called a substar, is an astronomical object, the mass of which is smaller than the smallest mass at which hydrogen fusion can be sustained (approximately 0.08 solar masses). This definition includes brown dwarfs and f ...
companion was discovered in an
eccentric Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off- center, in geometry * Eccentricity (graph theory) of a ...
orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...
. Incorporating more accurate
Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...
data yields a mass range for the companion to be anywhere from 10.27 to 29.9 times that of Jupiter. This confirms its substellar nature with the upper limit of mass putting it in the
brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...
range. The discovery of a second substellar companion—a
super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...
—was announced on 16 September 2018. It takes 6.27 days to complete its orbit and is the first exoplanet detected by the
Transiting Exoplanet Survey Satellite Transiting Exoplanet Survey Satellite (TESS) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission. It was launched on ...
(TESS) submitted for publication.


Planet-hosting stars

* HD 38283 (Bubup) is a Sun-like star of spectral type F9.5V of magnitude 6.7, located 124.3 ± 0.1 light-years distant. In 2011, a
gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...
with an Earth-like
orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...
of 363 days and a
minimum mass In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars, binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial velocit ...
a third that of Jupiter was discovered by the
radial velocity method Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in th ...
. * HD 39194 is an orange dwarf of spectral type K0V and magnitude 8.08, located 86.21 ± 0.09 light-years distant. Three planets in close orbit were discovered by the
High Accuracy Radial Velocity Planet Searcher The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. ...
(HARPS) in 2011. The three take 5.6, 14 and 34 days to complete an orbit around their star, and have minimum masses 3.72, 5.94 and 5.14 times that of the Earth respectively.


Variable stars

* TZ Mensae is an
eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved ...
that varies between magnitude 6.2 and 6.9 every 8.57 days. It is composed of two white main sequence stars in close orbit. One of these is of spectral type A0V, has a radius twice as that of the Sun and is 2.5 times as massive. The other, an A8V spectral type, has a radius 1.4 times that of the Sun and is 1.5 times as massive. * UX Mensae is another eclipsing binary system composed of two young stars around 1.2 times as massive as the Sun and 2.2 ± 0.5 billion years of age, orbiting each other every 4.19 days. The system is 338.2 ± 0.9 light-years distant. * TY Mensae is another eclipsing binary system classified as a
W Ursae Majoris variable A W Ursae Majoris variable, also known as a low mass contact binary, is a type of eclipsing binary variable star. These stars are close binaries of spectral types F, G, or K that share a common envelope of material and are thus in contact with one ...
; the two components are so close that they share a common envelope of stellar material. The larger star has been calculated to be 1.86 times as massive, have 1.85 times the diameter and is 13.6 times as luminous, while the smaller is 0.4 times as massive, 0.84 times the diameter, and 1.7 times as luminous as the Sun. Their surface temperatures have been calculated at 8164 and 7183 K respectively. * YY Mensae is an orange giant of spectral type K1III around 2.2 times as massive as the Sun, with 12.7 times its diameter and 70 times its luminosity. A rapidly rotating star with a period of 9.5 days, it is a strong emitter of X-rays and belongs to a class of star known as
FK Comae Berenices variables FK or fk may refer to: Arts and entertainment * Flyer Killer, fictional automated robots in the ''Terminator'' film franchise * Fox Kids, a former American children's television programming block * Funky Kong, a video game character Place * F ...
. These stars are thought to have formed with the merger of two stars in a contact binary system. With an apparent magnitude of 8.05, it is 707 ± 6 light-years distant. * AH Mensae is a
cataclysmic variable In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae (), since those with an outburst brightness visible to ...
star system composed of a white dwarf and a red dwarf that orbit each other every 2 hours 57 minutes. The stars are close enough that the white dwarf strips material off the red dwarf, creating an accretion disc that periodically ignites with a resulting brightening of the system. *
TU Mensae TU Mensae is a cataclysmic variable star of ( SU Ursae Majoris subtype) in the constellation Mensa. A close binary, it consists of a white dwarf and low-mass star orbiting each other in 2 hours 49 minutes. The stars are close enough that t ...
is another cataclysmic variable composed of a red dwarf and white dwarf. The orbital period of 2 hours 49 minutes is one of the longest for cataclysmic variable systems exhibiting brighter outbursts, known as
superhump In astronomy, a superhump is a periodic brightness variation in a cataclysmic variable star system, with a period within a few percent of the orbital period of the system. History Superhumps were first seen in SU Ursae Majoris (SU UMa) stars, a su ...
s. The normal outbursts result in an increase in brightness lasting around a day every 37 days, while the superhumps last 5–20 days and take place every 194 days. * AO Mensae is a faint star of magnitude 9.8. An
orange dwarf A K-type main-sequence star, also referred to as a K-type dwarf, or orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("r ...
that has 80% the size and mass of the Sun, it is also a
BY Draconis variable BY Draconis variables are variable stars of late spectral types, usually K or M, and typically belong to the main sequence. The name comes from the archetype for this category of variable star system, BY Draconis. They exhibit variations in thei ...
. These are a class of stars with
starspot Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in gene ...
s prominent enough that the star changes brightness as it rotates. It is a member of the
Beta Pictoris moving group The Beta Pictoris moving group is a young moving group of stars located relatively near Earth. A moving group, in astronomy, is a group of stars that share a common motion through space as well as a common origin. This moving group is named for Be ...
, a loose association of young stars moving across the galaxy.


Other stars

* WISE 0535−7500 is a
binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...
composed of two
sub-brown dwarf A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs (i.e. through the collapse of a gas cloud) but that has a planetary mass, therefore by definition below the limi ...
s of
spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...
cooler than Y1 located 47 ± 3 light-years away. Unable to be separated by observations to date, they are presumed to be of similar mass—8 to 20 times that of Jupiter—and are less than one AU apart.


Deep-sky objects

The
Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a dwarf galaxy and satellite galaxy of the Milky Way. At a distance of around , the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal Galaxy, Sagittarius Dwarf ...
lies partially within Mensa's boundaries, although most of it lies in neighbouring Dorado. It is a
satellite galaxy A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and Luminosity, luminous host galaxy (also known as the primary galaxy). Satellite galaxies and their constituents ...
of the Milky Way, located at a distance of 163,000 light-years. Among its stars within Mensa are
W Mensae W Mensae (W Men) is an unusual yellow supergiant star in the Large Magellanic Cloud in the southern constellation Mensa. It is an R Coronae Borealis variable and periodically decreases in brightness by several magnitudes. W Men is very ...
, an unusual yellow-white supergiant that belongs to a rare class of star known as a
R Coronae Borealis variable An R Coronae Borealis variable (abbreviated RCB, R CrB) is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation (a few tenths of a magnitude), and one irregular, unpredictably-sudden fading by 1 to 9 magni ...
, HD 268835, a blue
hypergiant A hypergiant ( luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term ''hypergiant'' is defined as luminosity class 0 (zero) in the MK ...
that is girded by a vast circumstellar disk of dust, and R71, a
luminous blue variable Luminous blue variables (LBVs) are rare, massive, evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of th ...
star that brightened in 2012 to over a million times as luminous as the Sun. Also within the galaxy is NGC 1987, a
globular cluster A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting ...
estimated to be around 600 million years old that has a significant number of red ageing stars, and
NGC 1848 Mensa is a constellation in the Southern Celestial Hemisphere near the south celestial pole, one of fourteen constellations drawn up in the 18th century by French astronomer Nicolas-Louis de Lacaille. Its name is Latin for table, though ...
, a 27 million year old
open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...
. Mensa contains several described open clusters, most of which can be only be clearly observed from large telescopes.
PKS 0637-752 PKS 0637-752 is a quasar located six billion light years in the constellation of Mensa. It is noted for having a bright and largest astrophysical jet at redshift of z = 0.651. Discovered by Einstein Observatory in 1980 through X-rays, PKS 0637-7 ...
is a distant quasar with a calculated
redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...
of z = 0.651. It was chosen as the first target of the then newly-operational
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 ...
in 1999. The resulting images revealed a gas jet approximately 330,000 light-years long. It is visible at
radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3  hertz (Hz) and 300  gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
, optical and
x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...
wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...
s.


Notes


References


Citations

*


External links


The Deep Photographic Guide to the Constellations: Mensa


{{DEFAULTSORT:Mensa (Constellation) Southern constellations Constellations listed by Lacaille