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.[19] 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).
Space motion
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.[20] This group has an estimated space velocity of 160km/s and is following a highly eccentric orbit through the Milky Way galaxy.[21]
Properties
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.[22]
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 of 7,800K 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.[6][7]
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 was observed by the Hubble Space Telescope, allowing its mass to be directly measured at 0.56±0.08M☉. 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.[7]
A survey with the Hubble Space Telescope revealed no visible orbiting companions, at least down to the limit of detection.[25][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.[24]
↑ Gliese, W.; Jahreiß, H. (1991). "Gl 440". Preliminary Version of the Third Catalogue of Nearby Stars. Archived from the original on 2016-03-04. Retrieved 2015-09-21.
↑ Perryman; etal. (1997). "HIP 57367". The Hipparcos and Tycho Catalogues. Archived from the original on 2016-03-04. Retrieved 2015-09-21.
↑ Luyten, Willem Jacob (1979). "LHS 30". LHS Catalogue, 2nd Edition. Archived from the original on 2016-03-04. Retrieved 2015-10-15.
↑ Luyten, Willem Jacob (1979). "NLTT 28447". NLTT Catalogue. Archived from the original on 2016-03-04. Retrieved 2015-10-15.
↑ Van Altena W. F.; Lee J. T.; Hoffleit E. D. (1995). "GCTP 2716". The General Catalogue of Trigonometric Stellar Parallaxes (Fourthed.). Archived from the original on 2016-03-04. Retrieved 2015-09-21.
↑ Perryman; etal. (1997). "HIP 57367". The Hipparcos and Tycho Catalogues. Archived from the original on 2016-03-04. Retrieved 2015-09-21.
↑ Hog; etal. (2000). "TYC 8981-4417-1". The Tycho-2 Catalogue. Archived from the original on 2016-03-04. Retrieved 2015-10-15.
↑ Eggen, O. J.; Greenstein, J. L. (1965). "Spectra, colors, luminosities, and motions of the white dwarfs". Astrophysical Journal. 141: 83–108. Bibcode:1965ApJ...141...83E. doi:10.1086/148091.— see table 5.
↑ Bell, R. A. (1962). "Observations of some southern white dwarfs". The Observatory. 82: 68–71. Bibcode:1962Obs....82...68B.
1 2 Siess, Lionel (2000). "Computation of Isochrones". Institut d'Astronomie et d'Astrophysique, Université libre de Bruxelles. Archived from the original on 2011-05-05. Retrieved 2007-03-24.
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