W Mensae
Encyclopedia
W Mensae is a variable star
in the southern constellation Mensa
. The star is classified as a yellow-white supergiant
(spectral class
F8 Iab).
W Mensae is very distant, being located in the neighboring galaxy Large Magellanic Cloud
. Despite its great luminosity
, the star has a maximum apparent brightness
of +13.8m, too dim to be visible even for a small telescope
. It belongs to the very rare R Coronae Borealis
class of variables which are often called "inverse nova
e" since they experience once a while very large drops in brightness. W Mensae is not an exception, since at minimum its brightness is less than +18.3m. The variability of the star was discovered in 1927 by W. J. Luyten
.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
in the southern constellation Mensa
Mensa (constellation)
Mensa is a constellation in the southern sky, created in the 18th century. Its name is Latin for table. It covers a keystone-shaped wedge of sky stretching from approximately 4h to 7.5h of right ascension, and −71 to −85.5 degrees of declination. Other than the south polar constellation...
. The star is classified as a yellow-white supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
(spectral class
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
F8 Iab).
W Mensae is very distant, being located in the neighboring galaxy Large Magellanic Cloud
Large Magellanic Cloud
The Large Magellanic Cloud is a nearby irregular galaxy, and is a satellite of the Milky Way. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center...
. Despite its great luminosity
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
, the star has a maximum apparent brightness
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of +13.8m, too dim to be visible even for a small telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...
. It belongs to the very rare R Coronae Borealis
R Coronae Borealis variable
A R Coronae Borealis variable is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation , and one irregular unpredictably sudden fading by 1 to 9 magnitudes...
class of variables which are often called "inverse nova
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
e" since they experience once a while very large drops in brightness. W Mensae is not an exception, since at minimum its brightness is less than +18.3m. The variability of the star was discovered in 1927 by W. J. Luyten
Willem Jacob Luyten
Willem Jacob Luyten was a Dutch-American astronomer.-Life:Jacob Luyten was born in Semarang, Java, at the time part of the Dutch East Indies. His mother was Cornelia M. Francken and his father Jacob Luyten, a French teacher.At the age of 11 he observed Halley's comet, which started his...
.