Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Musca [2] |
Right ascension | 11h 45m 42.91694s [3] |
Declination | −64° 50′ 29.4620″ [3] |
Apparent magnitude (V) | 11.50 [4] |
Characteristics | |
Spectral type | DQ6 [5] |
U−B color index | -0.59 [4] |
B−V color index | +0.19 [4] |
Astrometry | |
Proper motion (μ) | RA: 2661.640 mas/yr [3] Dec.: -344.933 mas/yr [3] |
Parallax (π) | 215.6753 ± 0.0181 mas [3] |
Distance | 15.123 ± 0.001 ly (4.6366 ± 0.0004 pc) |
Details | |
Mass | 0.56 ± 0.08 [6] M☉ |
Radius | 0.01 R☉ |
Luminosity | 0.0005 [7] L☉ |
Surface gravity (log g) | 8.27 ± 0.05 [7] cgs |
Temperature | 8,500 ± 300 [7] K |
Age | (as white dwarf) [7] 1.44 Gyr |
Other designations | |
Database references | |
SIMBAD | data |
Location of Gliese 440 in the constellation Musca |
Gliese 440, also known as LP 145-141 or LAWD 37, [4] is an isolated white dwarf located 15.1 light-years (4.6 parsecs ) from the Solar System in the constellation Musca. [16] According to a 2009 paper, it is the fourth closest known white dwarf to the Sun (after Sirius B, Procyon B, and van Maanen's star.) [17]
Gliese 440 is known at least from 1917, when its proper motion was published by R. T. A. Innes and H. E. Wood in Volume 37 of Circular of the Union Observatory. [18] The corresponding designation is UO 37. [10] (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).
Gliese 440 may be a member of the Wolf 219 moving group, which has seven possible members. These stars share a similar motion through space, which may indicate a common origin. [19] This group has an estimated space velocity of 160 km/s and is following a highly eccentric orbit through the Milky Way galaxy. [20]
White dwarfs are no longer generating energy at their cores through nuclear fusion, and instead are steadily radiating away their remaining heat. Gliese 440 has a DQ spectral classification, indicating that it is a rare type of white dwarf which displays evidence of atomic or molecular carbon in its spectrum. [21]
In 2019, Gliese 440 was observed passing in front of a more distant star. The bending of starlight by the gravitational field of Gliese 440 observed by the Hubble Space Telescope allowed its mass to be directly measured. The estimated mass of Gliese 440 is 0.56±0.08 M☉, which fits the expected range of a white dwarf with a carbon-oxygen core. This measurement marked the first direct gravitational mass determination of a single white dwarf. [6]
Gliese 440 has only 56% of the Sun's mass, [6] but it is the remnant of a massive main-sequence star that had an estimated 4.4 solar masses. [22] While it was on the main sequence, it probably was a spectral class B star (in the range B4–B9). [23] Most of the star's original mass was shed after it passed into the asymptotic giant branch stage, just prior to becoming a white dwarf.
A survey with the Hubble Space Telescope revealed no visible orbiting companions, at least down to the limit of detection. [24] [5]
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. [22]
Hipparcos-Gaia proper motion shows an anomaly that hints to the presence of an exoplanet that has a mass of either 0.44 or 0.60 MJ which is between Saturn and Jupiter. [25] [26]
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 of celestial objects on the sky. This permitted the first high-precision measurements of the intrinsic brightnesses, proper motions, and parallaxes of stars, enabling better calculations of their distance and tangential velocity. When combined with radial velocity measurements from spectroscopy, astrophysicists were able to finally measure all six quantities needed to determine the motion of stars. The resulting Hipparcos Catalogue, a high-precision catalogue of more than 118,200 stars, was published in 1997. The lower-precision Tycho Catalogue of more than a million stars was published at the same time, while the enhanced Tycho-2 Catalogue of 2.5 million stars was published in 2000. Hipparcos' follow-up mission, Gaia, was launched in 2013.
Gliese 570 is a quaternary star system approximately 19 light-years away. The primary star is an orange dwarf star. The other secondary stars are themselves a binary system, two red dwarfs that orbit the primary star. A brown dwarf has been confirmed to be orbiting in the system. In 1998, an extrasolar planet was thought to orbit the primary star, but it was discounted in 2000.
Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at about 8.7 light years from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.
HD 114729 is a Sun-like star with an orbiting exoplanet in the southern constellation of Centaurus. Based on parallax measurements, it is located at a distance of 124 light years from the Sun. It is near the lower limit of visibility to the naked eye, having an apparent visual magnitude of 6.68 The system is drifting further away with a heliocentric radial velocity of 26.3 km/s. The system has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.373″·yr−1.
Gliese 674(GJ 674) is a small red dwarf star with an exoplanetary companion in the southern constellation of Ara. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 9.38 and an absolute magnitude of 11.09. The system is located at a distance of 14.8 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −2.9 km/s. It is a candidate member of the 200 million year old Castor stream of co-moving stars.
Gliese 687, or GJ 687 (Gliese–Jahreiß 687) is a red dwarf in the constellation Draco. This is one of the closest stars to the Sun and lies at an approximate distance of less than 15 light years. Even though it is close by, it has a magnitude of about 9, so it can only be seen through a moderately sized telescope. Gliese 687 has a high proper motion, advancing 1.304 arcseconds per year across the sky. It has a net relative velocity of about 39 km/s. It is known to have a Neptune-mass planet. Old books and articles refer to it as Argelander Oeltzen 17415.
Gliese 673 is an orange dwarf star in the constellation Ophiuchus. It has a stellar classification of K7V. Main sequence stars with this spectra have a mass in the range of 60–70% of solar mass (M☉).
Pi Cassiopeiae, Latinized from π Cassiopeiae, is a close binary star system in the constellation Cassiopeia. It is visible to the naked eye with an apparent visual magnitude of +4.949. Based upon an annual parallax shift of 18.63 mas as seen from Earth, this system is located about 175 light years from the Sun.
Gliese 86 is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was orbiting the star.
Gliese 752 is a binary star system in the Aquila constellation. This system is relatively nearby, at a distance of 19.3 light-years.
Stein 2051 is a nearby binary star system, containing a red dwarf and a degenerate star, located in constellation Camelopardalis at about 18 ly from Earth.
HD 203842, also known as HR 8191 or rarely 30 G. Equueli, is a solitary, yellowish-white hued star located in the constellation Equuleus. It has an apparent magnitude of 6.32, placing it near the limit for naked eye visibility, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 374 light years, and it is currently drifting closer with a somewhat constrained heliocentric radial velocity of −21.8 km/s. At its current distance HD 203842's brightness is diminished by 0.15 magnitudes due to interstellar dust and it has an absolute magnitude of +1.06.
35 Pegasi is a single star in the northern constellation of Pegasus. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.80. The star is located approximately 155 light years away from the Sun based on parallax, and is drifting further away with a radial velocity of +54 km/s. The star has a relatively high proper motion, traversing the celestial sphere at the rate of 0.318 arc seconds per annum.
Gliese 809 is a red dwarf star in the constellation Cepheus, forming the primary component of a multi-star system. A visual magnitude of 8.55 makes it too faint to see with the naked eye. It is part of the Gliese Catalogue of Nearby Stars and is located about 23 light-years (ly) from the Solar System. Gliese 809 has about 70.5% the radius of the Sun and 61.4% of the Sun's mass. It has a metallicity of −0.06, which means that the abundance of elements other than hydrogen and helium is just 87.1% that of the Sun.
Gliese 180, is a small red dwarf star in the equatorial constellation of Eridanus. It is invisible to the naked eye with an apparent visual magnitude of 10.9. The star is located at a distance of 39 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −14.6 km/s. It has a high proper motion, traversing the sky at the rate of 0.765 arcseconds per year.
GJ 3323 is a nearby single star located in the equatorial constellation Eridanus, about 0.4° to the northwest of the naked eye star Psi Eridani. It is invisible to the naked eye with an apparent visual magnitude 12.20. Parallax measurements give a distance estimate of 17.5 light-years from the Sun. It is drifting further away with a radial velocity of +42.3 km/s. Roughly 104,000 years ago, the star is believed to have come to within 7.34 ± 0.16 light-years of the Solar System.
Gliese 251, also known as HIP 33226 or HD 265866, is a star located about 18 light years away from the Solar System. Located in the constellation of Gemini, it is the nearest star in this constellation. It is located near the boundary with Auriga, 49 arcminutes away from the bright star Theta Geminorum; due to its apparent magnitude of +9.89 it cannot be observed with the naked eye. The closest star to Gliese 251 is QY Aurigae, which is located 3.5 light years away.
Gliese 908 is a red dwarf star, located in constellation Pisces at 19.3 light-years from Earth. It is a BY Draconis variable star with a variable star designation of BR Piscium. Its apparent magnitude varies between magnitude 8.93 and magnitude 9.03 as a result of starspots and varying chromospheric activity.
HD 39194 is a star located in the southern circumpolar constellation Mensa. It has an apparent magnitude of 8.07, making it readily visible in binoculars but not to the naked eye. The object is relatively close at a distance of 86 light years but is receding with a heliocentric radial velocity of 13.9 km/s.