| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 09h 20m 29.01857s[1] |
| Declination | −09° 33′ 20.5054″[1] |
| Apparent magnitude (V) | 4.818[2](4.91 + 7.03 + 10.99)[3] |
| Characteristics | |
| Evolutionary stage | red clump[4] |
| Spectral type | K0III[5] + F4V + K2V[6] |
| Astrometry | |
| Radial velocity (Rv) | +25.60±0.13[7] km/s |
| Proper motion (μ) | RA: −12.48[1]mas/yr Dec.: −27.37[1]mas/yr |
| Parallax (π) | 14.66±0.31 mas[1] |
| Distance | 222 ± 5 ly (68 ± 1 pc) |
| Details | |
| A | |
| Mass | 2.17[2] M☉ |
| Radius | 11[7] R☉ |
| Luminosity | 57.5[2] L☉ |
| Surface gravity (log g) | 2.9[7] cgs |
| Temperature | 4,965±26[2] K |
| Metallicity[Fe/H] | −0.07[7] dex |
| Rotational velocity (v sin i) | 3.3[7] km/s |
| Age | 1.91[2] Gyr |
| B | |
| Radius | 1.82[8] R☉ |
| Luminosity | 5.885[8] L☉ |
| Temperature | 6,664[8] K |
| C | |
| Radius | 0.72[9] R☉ |
| Luminosity | 0.227[9] L☉ |
| Temperature | 4,685[9] K |
| Other designations | |
| CCDM J09204-0934,WDS J09204-0934[10] | |
| A:27 Hya,BD−08°2643,HD 80586,HIP 45811,HR 3709,SAO 136768 | |
| B:BD−09°2801,HD 80550,HIP 45802,SAO 136767 | |
| C:TYC 5463-1518-1 | |
| Database references | |
| SIMBAD | data |
| B | |
| C | |
27 Hydrae is atriple star system[6] system in theequatorialconstellation ofHydra,[10] located 222 light years away from the Sun.[1] It is visible to the naked eye as a faint, orange-hued star with a combinedapparent visual magnitude of 4.82.[2] The system is moving further from the Earth with a heliocentricradial velocity of +25.6 km/s.[7]
The magnitude 4.91[6] primary, component A, is an aginggiant star with astellar classification of K0 III.[5] It is ared clump giant,[4] which indicates it is on thehorizontal branch and is generating energy throughhelium fusion at itscore. The star is 1.9[2] billion years old with 2.17[2] times themass of the Sun. It has swelled to 11[7] times theSun's radius and is radiating 57.5[2] times theSun's luminosity from its enlargedphotosphere at aneffective temperature of 4,965 K.[2] The star is suspected to host alow-mass companion.[11]
The stellar companions to this star, designated components B and C, lie at anangular separation of229.10″ from the primary, and form a binary pair with a separation of 9.20″ as of 2015.[3] The brighter member of the pair, component B, is a seventh magnitudeF-type main-sequence star with a class of F4 V, while its companion is an eleventh magnitudeK-type main-sequence star with a class of K2 V.[6]
TheOkayama Planet Search team published a paper in late 2008 reporting investigations into radial velocity variations observed for a set of evolved stars, showing hints of asubstellar companion orbiting the primary member of the widebinary system 27 Hydrae.[11] Itsorbital period is estimated at 9.3 years, but no planet has been confirmed yet.
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b(unconfirmed) | ≥10MJ | ≈5.9 | 3,400 | — | — | — |
