Ross 248
Star in the constellation Andromeda
From Wikipedia, the free encyclopedia
Ross 248, also called HH Andromedae or Gliese 905, is a red dwarf star approximately 10.30 light-years (3.16 parsecs)[10] from Earth in the northern constellation of Andromeda. Despite its proximity it is too dim to be seen with the naked eye.[11] It was first catalogued by Frank Elmore Ross in 1926 with his second list of proper-motion stars.[12] It was too dim to be included in the Hipparcos survey. In about 40,000 years, Voyager 2 will pass 1.7 light-years (9.7 trillion miles) from the star.
  Ross 248 Location of Ross 248 in the constellation Andromeda | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 23h 41m 55.03630s[1] |
| Declination | +44° 10′ 38.8189″[1] |
| Apparent magnitude (V) | 12.23 - 12.34[2] |
| Characteristics | |
| Spectral type | M6 V[3] |
| U−B color index | +1.48[citation needed] |
| B−V color index | +1.92[citation needed] |
| Variable type | BY Dra[2] |
| Astrometry | |
| Radial velocity (Rv) | −77.29±0.19[1] km/s |
| Proper motion (μ) | RA: 112.527 mas/yr[1] Dec.: −1,591.650 mas/yr[1] |
| Parallax (π) | 316.4812±0.0444 mas[1] |
| Distance | 10.306 ± 0.001 ly (3.1597 ± 0.0004 pc) |
| Absolute magnitude (MV) | 14.79[4] |
| Details | |
| Mass | 0.145[5] M☉ |
| Radius | 0.190[5] R☉ |
| Luminosity | 0.0022[6] L☉ |
| Surface gravity (log g) | 5.13[6] cgs |
| Temperature | 2,930[5] K |
| Metallicity [Fe/H] | +0.23[5] dex |
| Rotation | 2.07±0.01[7] days |
| Rotational velocity (v sin i) | 0.1[8] km/s |
| Age | 2.6[5] Gyr |
| Other designations | |
| HH Andromedae, HH And, 2MASS J23415498+4410407, G 171-010, GCTP 5736.00, GJ 905, LHS 549.[9] | |
| Database references | |
| SIMBAD | data |
Within the next 80,000 years, Ross 248 is predicted to be the nearest star to the Sun for around 9,000 years, overtaking the current nearest star, the triple system Alpha Centauri.
Characteristics
This star has about 14% of the Sun's mass and 19% of the Sun's radius, but only 0.2% of the Sun's luminosity. It has a stellar classification of M6 V,[3] which indicates it is a type of main-sequence star known as a red dwarf. This is a chromospherically-active star.[14] With high probability, there appears to be a long-term cycle of variability with a period of 4.2 years. This variability causes the star to range in visual magnitude from 12.23 to 12.34.[13] In 1950, this became the first star to have a small variation in magnitude attributed to spots on its photosphere as it rotates,[15] a class known as BY Draconis variables.[2]
Examining the proper motion of Ross 248 has found no evidence of a brown dwarf or stellar companion orbiting between 100–1,400 AU,[16] and other unsuccessful searches have been attempted using both the Hubble Space Telescope Wide Field Planetary Camera[4] and by near-infrared speckle interferometry.[17] Long-term observations by the Sproul Observatory show no astrometric perturbations by any unseen companion.[15]
Distance from the Sun
The space velocity components of this star in the galactic coordinate system are [U, V, W] = [−32.9±0.7, −74.3±1.3, 0.0±1.4] km/s.[10] The trajectory of Ross 248 will bring it closer to the Solar System. In 1993, Matthews projected that in about 33,000 years it would enter a period of about 9,000 years as the closest star to the Sun, as close as 3.024 light-years (0.927 parsecs) in 36,000 years.[18] A more precise estimate in 2022 has it approaching to within 3.048 ly (0.9345 pc) in 36,500 years.[19]
Any future spacecraft that escaped the Solar System with a velocity of 25.4 km/s would reach this star 37,000 years from now, when the star just passes its nearest approach. By comparison, the Voyager 1 has an escape velocity of 16.6 km/s.[20]
Voyager 2 is not headed toward any particular star, although in roughly 42,000 years, it will pass the star Ross 248 at a distance of 1.7 light-years.[21]
The closest stellar neighbors to Ross 248 are the binary systems Groombridge 34, at 1.8 light-years away, and Kruger 60, at 4.5 light-years.[22]
