30 Arietis
Multiple star system in the constellation Aries
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30 Arietis (abbreviated 30 Ari) is a 6th-apparent-magnitude multiple star system[5] in the constellation of Aries. 30 Arietis is the Flamsteed designation. 30 Arietis A and B are separated by 38.1″, or about 1,700 AU at a distance of 145 light-years away. The main components of both systems are both binaries with composite spectra belonging to F-type main-sequence stars, meaning they are fusing hydrogen in their cores. 30 Arietis B also has a second stellar companion, making a total of five stars. The 30 Arietis system is 910 million years old, one fifth the age of the Sun.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aries |
| 30 Arietis A | |
| Right ascension | 02h 37m 00.5235s[1] |
| Declination | +24° 38′ 49.990″[1] |
| Apparent magnitude (V) | 6.50[2] |
| 30 Arietis B | |
| Right ascension | 02h 36m 57.7454s[3] |
| Declination | +24° 38′ 53.000″[3] |
| Apparent magnitude (V) | 7.09[2] |
| Characteristics | |
| Spectral type | F5 V / F6 V[4] |
| B−V color index | 0.410 / 0.510[4] |
| Astrometry | |
| 30 Arietis A | |
| Radial velocity (Rv) | +24.71±7.77[1] km/s |
| Proper motion (μ) | RA: +136.866 mas/yr[1] Dec.: −15.349 mas/yr[1] |
| Parallax (π) | 22.2608±0.0309 mas[1] |
| Distance | 146.5 ± 0.2 ly (44.92 ± 0.06 pc) |
| 30 Arietis B | |
| Radial velocity (Rv) | +12.38±0.31[3] km/s |
| Proper motion (μ) | RA: +140.951 mas/yr[3] Dec.: −10.536 mas/yr[3] |
| Parallax (π) | 22.5107±0.0315 mas[3] |
| Distance | 144.9 ± 0.2 ly (44.42 ± 0.06 pc) |
| Orbit[5][6] | |
| Primary | 30 Arietis A |
| Name | 30 Arietis BC |
| Period (P) | 34000 yr |
| Semi-major axis (a) | 40" (1670 AU) |
| Orbit[6] | |
| Primary | 30 Arietis B |
| Name | 30 Arietis C |
| Period (P) | 80 yr |
| Semi-major axis (a) | 22.3 AU |
| Orbit[7] | |
| Primary | 30 Arietis B |
| Name | 30 Arietis Bb |
| Period (P) | 339.7+0.3 −0.2 d (0.930±0.001 yr) |
| Semi-major axis (a) | 1.05±0.01 AU |
| Eccentricity (e) | 0.45±0.04 |
| Inclination (i) | 2.9±0.3° |
| Longitude of the node (Ω) | 39.0+6.4 −6.3° |
| Periastron epoch (T) | 2458000.5+13.6 −16.0 BJD |
| Argument of periastron (ω) (secondary) | 354+8 −9° |
| Semi-amplitude (K1) (primary) | 281+27 −25 km/s |
| Details | |
| 30 Arietis A | |
| Mass | 1.31 ± 0.04[4] M☉ |
| Radius | 1.37 ± 0.03[4] R☉ |
| Age | 860±630[6] Myr |
| 30 Arietis Ba | |
| Mass | 1.16 ± 0.04[4] M☉ |
| Radius | 1.13 ± 0.03[4] R☉ |
| Age | 910±830[6] Myr |
| 30 Arietis Bb | |
| Mass | 188.1+19.7 −18.5[7] MJup |
| Other designations | |
| CCDM 02370+2439, WDS 02370+2439 | |
| 30 Arietis A: BD+24°376, HD 16246, HIP 12189, HR 765, SAO 75471 | |
| 30 Arietis B: BD+24°375, HD 16232, HIP 12184, HR 764, SAO 75470 | |
| Database references | |
| SIMBAD | A |
| B | |
| Exoplanet Archive | data |
Star system
30 Arietis A and B are separated by 38.1", corresponding to 1,700 AU at a distance of 145 light-years. The pair are at almost the same distance, have very similar proper motions, and are considered almost certain to be gravitationally bound with a likely period around 34,000 years.[6] The main components of both systems are both binaries with composite spectra belonging to F-type main-sequence stars, meaning they are fusing hydrogen in their cores.[4]
30 Arietis A is a spectroscopic binary with an orbital period of 1.1 days.[8] The primary Aa is an F-type main sequence star about 31% more massive than the Sun, while the companion Ab is a faint red dwarf only about 15% the mass of the Sun.
30 Arietis B has been reported to have a red dwarf companion C at a distance of 22 AU,[6] and another companion Bb at about 1 AU.[4] 30 Arietis Bb has a minimum mass consistent with a giant planet, but in 2020, after the orbital inclination was measured, the "planet" was found to fall in the mass range of a red dwarf star.[9] The more distant companion is referred to as C to distinguish it from Bb, and at about 0.5" it has been imaged using adaptive optics.[6]
30 Arietis Bb
30 Arietis Bb (sometimes abbreviated 30 Ari Bb) is a red dwarf which orbits the F-type main sequence star 30 Arietis Ba. The red dwarf, initially believed to be a massive planet or brown dwarf, was announced in a paper published online on September 24, 2009. It was discovered by using precision radial velocity measurements from the echelle spectrograph installed on the Alfred-Jensch Telescope in Karl Schwarzschild Observatory.[4] The object has a minimum mass of nearly 10 times that of Jupiter.[10] In 2020, after the inclination of the planetary orbit was measured to be just 4.14+0.96
−0.90°, the "planet" was found to fall in the mass range of red dwarf stars.[9]