LP 145-141
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Gliese 440, also known as LP 145-141 or LAWD 37, is a
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
located from the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
in the constellation
Musca is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe in diameter p ...
, the nearest star in this constellation. It is the fourth closest white dwarf, after
Sirius B Sirius is the brightest star in the night sky. Its name is derived from the Greek word (Latin script: ), meaning 'glowing' or 'scorching'. The star is designated  Canis Majoris, Latinized to Alpha Canis Majoris, and abbre ...
, Procyon B, and van Maanen's star. Despite its closeness, Gliese 440 is intrinsically faint with just 0.05% the
luminosity of the Sun The solar luminosity () is a unit of radiant flux ( power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun. One nominal s ...
, and can not be viewed to the
naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...
with an
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 +11.5.


History of observations

Gliese 440 is known at least from 1917, when its
proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
was published by R. T. A. Innes and H. E. Wood in Volume 37 of ''Circular of the Union Observatory''. The corresponding designation is UO 37. (Note: this designation is not unique for this star, that is all other stars, listed in the table in the Volume 37 of this Circular, also could be called by this name).


Space motion

Gliese 440 may be a member of the Wolf 219
moving group In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...
, which has seven possible members. These stars share a similar motion through space, which may indicate a common origin. This group has an estimated space velocity of 160 km/s and is following a highly
eccentric orbit In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless quantity, dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circu ...
through the
Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...
galaxy.


Properties

White dwarfs are no longer generating energy at their cores through
nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
, and instead are steadily radiating away their remaining heat. Gliese 440 has a DQ
spectral classification ''Spectral'' is a 2016 Hungarian-American military science fiction action film co-written and directed by Nic Mathieu. Written with Ian Fried & George Nolfi, the film stars James Badge Dale as DARPA research scientist Mark Clyne, with Max M ...
, indicating that it is a rare type of white dwarf which displays evidence of atomic or molecular
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
in its spectrum. Gliese 440 is small and faint, like typical white dwarfs, having just 0.0127 times the Sun's radius (1.4 times Earth's radius) and 0.05 percent the Sun's luminosity. Gliese 440 currently has an
effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...
of and will cool as its residual heat escape to the cosmos. The rate of cooling allows its age in the white dwarf stage to be estimated at 1.2 billion years. In 2019, Gliese 440 was observed passing in front of a more distant star. The
bending of starlight Tests of general relativity serve to establish observational evidence for the theory of general relativity. The first three tests, proposed by Albert Einstein in 1915, concerned the "anomalous" precession of the perihelion of Mercury, the bendin ...
by the gravitational field of Gliese 440 was observed by the
Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
, allowing its mass to be directly measured at . The mass fits the expected range of a white dwarf with a carbon-oxygen core. This was the second mass determination of a white dwarf using this method, after Stein 2051 B. Gliese 440 is the remnant of a massive
B-type star 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 ...
that had an estimated 4.4
solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...
es. While it was on the
main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...
, it probably was a
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 ...
B star (in the range B4–B9). Most of the star's original mass was shed after it passed into the
asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...
stage, just prior to becoming a white dwarf.


Search for companions

A survey with the
Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...
revealed no visible orbiting companions, at least down to the limit of detection. Its proximity, mass and temperature have led to it being considered a good candidate to look for Jupiter-like planets. Its relatively large mass and high temperature mean that the system is relatively short-lived and hence of more recent origin.
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 ...
-
Gaia In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...
proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
shows an anomaly that hints to the presence of an
exoplanet 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 det ...
that has a mass of either 0.44 or 0.60 which is between Saturn and Jupiter.


See also

*
List of nearest stars This list covers all known stars, white dwarfs, brown dwarfs, and sub-brown dwarfs within of the Sun. So far, 131 such objects have been found. Only List of nearest bright stars, 22 are bright enough to be visible without a telescope, for whi ...
* List of exoplanets and planetary debris around white dwarfs


References


External links


CC 658
{{Musca Local Bubble Musca White dwarfs 057367 0440