81 Cancri
Template:Short description Template:Other stars by Bayer designation
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Cancer |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | 6.49[2] |
| Characteristics | |
| Spectral type | G8V[3] + K1V[3] / L8[4][5] + ~L8[5] |
| B−V Template:Engvar | 0.731±0.004[2] |
| Variable type | Constant[2] |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[6] km/s |
| Proper motion (μ) | RA: −523.619 mas/yr[1] Dec.: +244.282 mas/yr[1] |
| Parallax (π) | 49.1493±0.3467 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | +4.95[2] |
| Orbit[6] | |
| Primary | 81 Cancri A |
| Companion | 81 Cancri B |
| Period (P) | Script error: No such module "val". |
| Semi-major axis (a) | 115.4±0.63″ |
| Eccentricity (e) | 0.433256±0.0034 |
| Inclination (i) | 124.1±0.64° |
| Longitude of the node (Ω) | 317.6±0.46° |
| Periastron epoch (T) | 1982.690±0.0040 |
| Argument of periastron (ω) (secondary) | 170.731±0.81° |
| Argument of periastron (ω) (primary) | 350.731±0.81° |
| Semi-amplitude (K1) (primary) | 11.4908±0.11 km/s |
| Semi-amplitude (K2) (secondary) | 12.1317±0.14 km/s |
| Details | |
| 81 Cnc A | |
| Mass | Script error: No such module "val".[6] Template:Solar mass |
| Radius | 0.82[7] Template:Solar radius |
| Luminosity | 1.03[2] Template:Solar luminosity |
| Surface gravity (log g) | 4.55[7] cgs |
| Temperature | 5,430[7] K |
| Metallicity [Fe/H] | −0.28[7] dex |
| 81 Cnc B | |
| Mass | Script error: No such module "val".[6] Template:Solar mass |
| Radius | 0.81[7] Template:Solar radius |
| Surface gravity (log g) | 4.56[7] cgs |
| Temperature | 5,360[7] K |
| Metallicity [Fe/H] | Script error: No such module "val".[7] dex |
| Other designations | |
| Template:Odlist | |
| Database references | |
| SIMBAD | data |
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81 Cancri is a stellar system in the zodiac constellation of Cancer. It has the Bayer designation Pi1 Cancri, which is Latinized from π1 Cancri, and abbreviated Pi1 Cnc or π1 Cnc; 81 Cancri is the star's Flamsteed designation. The main component of the system is a close binary, while a brown dwarf binary is located at a wide separation. The primary is just bright enough to be visible to the naked eye, having an apparent visual magnitude of 6.49.[2] Its position near the ecliptic means it is subject to lunar occultations.[8]
Based on parallax measurements, this system is located at a distance of Script error: No such module "convert". from the Sun. HD 164595 has a large proper motion, traversing the celestial sphere at an angular rate of Script error: No such module "val". yr−1.[9] It is drifting further away with a line of sight velocity of 49.8 km/s.[6]
Components
81 Cancri was found to be a close visual binary by W. S. Finsen in 1959.[10] Their orbit has a period of Script error: No such module "convert". with an eccentricity of 0.433. The primary is a G-type main-sequence star with a stellar classification of G8V.[3] It has 89%[6] of the mass of the Sun and 82% of the Sun's radius.[7] This star is radiating a similar luminosity as the Sun from its photosphere with an effective temperature of 5,430 K.[7] The secondary is a K-type main-sequence star with a class of K1V.[3] It has a similar mass and temperature as the primary, being only Template:Solar mass lower in mass and a few hundred kelvin cooler.
A brown dwarf component in the system was detected in 2001.[4] The source 2MASSW J0912145+145940 (2M0912+14) in the 2MASS catalogue was identified as having a common proper motion with the AB binary, and subsequent observations confirmed the brown dwarf nature of the companion. The new component, 81 Cancri C, was found to have a spectral type of L8, near to the L-T transition. Separated from the primary components by 43 arcseconds and at a distance of 20.4 parsecs, the brown dwarf has a minimum physical separation of approximately 880 AU.
The brown dwarf was found to be about half a magnitude brighter in the JHK bands than expected, compared to others of similar spectral type and known distance. The system was not found to not be particularly young to some confidence, so it was possible that component C could itself be a close binary not resolved by 2MASS. This was confirmed in 2006[5] as the source was found to be slightly oblong, caused by two components of similar spectral types. These two brown dwarfs, components C and D, have a separation of approximately 11 AU, and their mutual orbit likely takes on order of 150 years due to the small masses involved.
See also
References
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