Discover

'GJ 440' (also known by the designation WD 1142-645) is a white dwarf located 15 light years from the solar system.^[1] A white dwarf is a star that is no longer generating energy at its core through nuclear fusion, and instead is steadily radiating away its remaining heat. GJ 440 has a DQ spectral classification—a rare type of white dwarf that displays evidence of atomic or molecular carbon in its spectrum.^[2]
This star has only 50% of the Sun's mass, but it is the remnant of a massive main sequence star that had an estimated 4.4 solar masses.^[3] While it was on the main sequence, it probably was a spectral class B star (in the range B6-B9).^[4] Most of the star's original mass was shed after it passed into the red giant 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.^[5]
GJ 440 may be a member of the Wolf 219 moving group that has seven possible members. These stars share a similar motion through space, which may indicate a common origin.^[6] The groups has an estimated space velocity of 160 km/s and are following highly eccentric orbits around the Milky Way galaxy.^[7]

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References

References

1. The Solar Neighborhood. VI. New Southern Nearby Stars Identified by Optical Spectroscopy, Henry, Todd J.; Walkowicz, Lucianne M.; Barto, Todd C.; Golimowski, David A., , , The Astronomical Journal, 2002
2. White Dwarf Stars, Kawaler, S.; Dahlstrom, M., , , American Scientist, 2000
3. Imaging planets around nearby white dwarfs, Burleigh, M. R.; Clarke, F. J.; Hodgkin, S. T., , , Monthly Notices of the Royal Astronomical Society, 2002
4. Computation of Isochrones
5. A Search for Faint Companions to Nearby Stars Using the Wide Field Planetary Camera 2, D. J. Schroeder ''et al'', , , The Astronomical Journal, 2000
6. Spectra, colors, luminosities, and motions of the white dwarfs, Eggen, O. J.; Greenstein, J. L., , , Astrophysical Journal, 1965 — see table 5.
7. Observations of some southern white dwarfs, , R. A., Bell, The Observatory, 1962