Ross 154

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Ross 154
Observational Data
Designation HIP 92403
Right ascension 18h 49m 49.36216s[1]
Declination -23° 50′ 10.4291″[1]
Constellation Sagittarius
Type of object Red dwarf
Magnitude Apparent Mag: +10.95
Absolute Mag: +13.59[2]
Astrometry
Distance from Earth 9.68 ly[3]
Radial velocity -10.5±0.1 km/s[1]
Proper motion RA: 637.02 mas/yr[1]
Dec.: -191.64 mas/yr[1]
Parallax 336.72±2.03 mas[1]

Ross 154 is a red dwarf star which is the seventh closest to our Sun. The star is located 9.7 light years away in the constellation of Sagittarius. Because it is a dim, cool red star, it has an apparent magnitude of only 10.95. It is therefore invisible to the unaided eye and requires a 65 mm telescope aperture to be seen. Ross 154 was first discovered in 1925 by Frank Elmore Ross.

Ross 154 is a cool, dim, red dwarf main sequence star of spectral type of M3.5 Ve.[1] The star has some 17 percent of the mass of our Sun, and around 19 to 24 percent of its diameter.[4] Like all class M dwarfs, Ross 154 emits much of its electromagnetic energy in the infrared, with only 5/10,000th of our Sun's visual luminosity.

Ross 154 is a fast rotating star, indicating that it may be less than a billion years in age.[5] The star also has a low velocity relative to the Sun, further showing that it is likely a Population I star.[6] The star only contains around 56 percent of the metallicity of our Sun, based on its abundance of iron.[7] Ross 154 is also a flare star, and will increase its output of x-rays greatly during a flare. As such, the star is often observed using various X-ray observatories such as the Chandra observatory.

There are no known substellar companions around Ross 154. For an Earth-like planet to have liquid water on its surface, such a world would need to be in a close orbit, centered around 0.19 AU if one accounts for the large amount of infrared radiation from Ross 154. Such a world would orbit Ross 154 in 73 days and would be tidally locked to the star.[8] Because Ross 154 is a flare star known for extreme increases in x-rays during flares, it would be unlikely for life as we understand it to survive on such a hypothetical world.

Because of the proximity of Ross 154 to our own solar system, the star is a "Tier 1" target star for NASA's future optical Space Interferometry Mission to detect smaller worlds in relative close orbit around stars. The ESA's future Darwin mission will serve a similar purpose.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Ross 154 from the SIMBAD Astronomical Database
  2. From definition of absolute magnitude, using apparent magnitude (+10.95) and distance (9.68 ly) given here.
  3. Calculated from given parallax of 336.72 mas.
  4. Johnson, H. and Wright, C. (1983). Predicted infrared brightness of stars within 25 parsecs of the sun. The Astrophysical Journal Supplement Series, 53, p.643. Bibcode:1983ApJS...53..643J
  5. Wargelin, B., Kashyap, V., Drake, J., García-Alvarez, D. and Ratzlaff, P. (2008). X-Ray Flaring on the dMe Star, Ross 154. The Astrophysical Journal, 676(1), pp.610-627. arXiv:0712.2791
  6. Veeder, G. (1974). Old disk flare stars. The Astronomical Journal, 79, p.702. Bibcode:1974AJ.....79..702V
  7. Eggen, O. (1996). Distribution and Corrlation of Age, Abundance, and Motion of Lower Main Sequence Stars. The Astronomical Journal, 111, p.466. Bibcode:1996AJ....111..466E
  8. arXiv:astro-ph/0504497