61 Ursae Majoris

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61 Ursae Majoris
Stellar characteristics
ConstellationUrsa Major
Right ascension (Epoch J2000)11h 41m 03.02s
Declination (Epoch J2000)+34° 12' 05.89"
Spectral typeG8 Ve
Distance from Sol31.1 ly
Other designations61 UMa, HR 4496, Gl 434, Hip 56997, HD 101501, BD+35 2270, SAO 62655, FK5 1300, LTT 13200.
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61 Ursae Majoris is located about 31.1 light-years from Sol. It lies in the southeastern corner of the constellation Ursa Major, the Great Bear, which also encompasses the Big Dipper or Plow (Plough). The star is a yellow-orange main sequence dwarf star of spectral and luminosity type G8 Ve, with about 81 percent of Sol's mass, 84 to 89 percent of its diameter[1][2], and around 57 percent of its luminosity. The star may be only 40 to 105 percent as enriched as Sol with elements heavier than hydrogen ("metallicity"), based on its abundance of iron[3]. It is a New Suspected Variable star designated as NSV 5291. While chromospheric activity measurements suggest that the star may be as young as 500 million years[4], the lack of an easily observable dust disk -- as is found at Epsilon Eridani -- suggests that the stars could be well over a billion years old.

The failure, thus far, to find large substellar objects like brown dwarfs or a Jupiter- or Saturn-class planet in a "torch" orbit (closer than the Mercury to Sun distance) around 61 Ursae Majoris -- with even the highly sensitive radial-velocity methods of Geoffrey W. Marcy and R. Paul Butler -- bodes well for the possibility of Earth-type terrestrial planets around this star[5]. The orbit of an Earth-like planet (with liquid water) around this star would be centered around 0.77 AU -- somewhat farther than the orbital distance of Venus in the Solar System -- with an orbital period under 273 days or more than two thirds of an Earth year. However, if this star is as young as chromospheric activity alone would suggest, then it is likely that only primitive organisms like bacteria that can survive heavy meteorite or cometary bombardment would be likely to survive on any Earth-type planet that has cooled sufficiently to allow carbon-based lifeforms to develop.

(Data from SolStation.com)


  1. (Morossi and Malagnini, 1985, page 369)
  2. (Johnson and Wright, 1983, page 673)
  3. (Cayrel de Strobel et al, 1991, page 292)
  4. (see HD 101501 in Table 2 from Don Barry, 1988)
  5. (Cumming et al, 1999)