Gliese 436
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Leo |
| Right ascension | 11h 42m 11.0941s[1] |
| Declination | +26° 42′ 23.652″[1] |
| Apparent magnitude (V) | 10.67[2] |
| Characteristics | |
| Spectral type | M2.5 V[2] |
| Apparent magnitude (B) | ~12.20[1] |
| Apparent magnitude (V) | ~10.68[1] |
| Apparent magnitude (J) | 6.900 ±0.024[1] |
| Apparent magnitude (H) | 6.319 ±0.023[1] |
| Apparent magnitude (K) | 6.073 ±0.016[1] |
| B−V color index | 1.52[2] |
| Astrometry | |
| Radial velocity (Rv) | 10[1] km/s |
| Proper motion (μ) | RA: 896.34[1] mas/yr Dec.: −813.70[1] mas/yr |
| Parallax (π) | 97.73 ± 2.27[1] mas |
| Distance | 33.4 ± 0.8 ly (10.2 ± 0.2 pc) |
| Absolute magnitude (MV) | 10.63[2] |
| Details | |
| Mass | 0.41±0.05[2] M☉ |
| Radius | 0.42[3] R☉ |
| Luminosity | 0.019 L☉ |
| Temperature | 3318[3] K |
| Metallicity | [M/H]=-0.32[4] |
| Rotation | <3 km/s[2] |
| Age | 6.5–9.9×109[5] years |
| Other designations | |
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Ross 905, GJ 436, LTT 13213, GCTP 2704.10, LHS 310, AC+27:28217, Vyssotsky 616, HIP 57087, GEN# +9.80120068, LP 319-75, G 121-7, LSPM J1142+2642, 1RXS J114211.9+264328, ASCC 683818, G 147-68, UCAC2 41198281, BPS BS 15625-0002, G 120-68, 2MASS J11421096+2642251, USNO-B1.0 1167-00204205, CSI+27-11394, MCC 616, VVO 171, CSI+27-11395, HIC 57087, NLTT 28288, Zkh 164, CSI+26-11395, [RHG95] 1830, GCRV 7104, LFT 838, PM 11395+2700[1]
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| Database references | |
| SIMBAD | data |
| Extrasolar Planets Encyclopaedia |
data |
Gliese 436 is a red dwarf star approximately 33 light-years away in the constellation of Leo. In 2004, the existence of an extrasolar planet orbiting the star was confirmed. There are indications that there may be an additional low-mass planet in the system, but this is not yet confirmed.
Contents |
Star
Stellar models for this star give an estimated size of about 42% of the Sun's radius. The same model predicts a surface temperature of about 3318 K.[3] Gl 436 is older than the Sun by several billion years but it only has an abundance of heavy elements (with masses greater than helium-4) equal to 44%[4] of the Sun's. The projected rotation velocity is less than 3 km/s, and the chromosphere has only a low level of magnetic activity.[2]
This star is a member of the "old-disk population" with velocities in the galactic coordinate system of U=+44, V=−20 and W=+20 km/s.[2]
Planetary system
The star is orbited by one known planet, designated Gliese 436 b. The planet has an orbital period of 2.6 Earth Days and transits the star as viewed from Earth. It has a mass of 22.2 times Earth's Mass and is roughly 55,000 km in diameter, giving it a mass and radius similar to the ice giant planets Uranus and Neptune in our solar system. In general, Doppler spectroscopy measurements do not measure the true mass of the planet, but instead measure the product m sin i, where m is the true mass and i is the inclination of the orbit (the angle between the line-of-sight and the normal to the planet's orbital plane), a quantity that is generally unknown. However, for Gliese 436 b, the transits enable the determination of the inclination, as they show that the planet's orbital plane is very nearly in the line of sight (i.e. that the inclination is close to 90 degrees). Hence the mass quoted is the actual mass. The planet is thought to be largely composed of hot ices with an outer envelope of hydrogen and helium, and is termed a "hot Neptune".[6] The planet's orbit is eccentric. Because tidal forces would tend to circularise the orbit of the planet on short timescales, this suggested that Gliese 436 b is being perturbed by an additional planet orbiting the star.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | 0.041 ± 0.05 MJ | 0.0291 ± 0.0004 | 2.64385 ± 0.00009 | 0.150 ± 0.012 |
Possible second planet
In 2008, a second planet, designated "Gliese 436 c" was claimed to have been discovered, with an orbital period of 5.2 days and an orbital semimajor axis of 0.045 AU.[8] The planet was thought to have a mass of roughly 5 Earth masses and have a radius about 1.5 times larger than the Earth's.[9] Despite being announced in the media as being the smallest known extrasolar planet, it would still have been more massive than the three planets orbiting the pulsar PSR B1257+12, which have been known since 1992. Due to its size, the planet was thought to be a rocky, terrestrial planet.[10] Gliese 436 c was announced by Spanish scientists in April 2008 by analyzing its influence on the orbit of Gliese 436 b.[9] Further analysis showed that the transit length of the inner planet is not changing, a situation which rules out most possible configurations for this system. Also, if it did orbit at these parameters, the system would be the only "unstable" orbit on UA's Extrasolar Planet Interactions chart. The existence of this "Gliese 436 c" was thus regarded as unlikely,[11] and the discovery was eventually retracted at the Transiting Planets conference in Boston, 2008.[12]
Despite the retraction, studies have concluded that the possibility that there is an additional planet orbiting Gliese 436 remains plausible.[13] With the aid of an unnoticed transit automatically recorded at NMSU on January 11, 2005, and observations by amateur astronomers, it has been suggested that there is a trend of increasing inclination of the orbit of Gliese 436 b, though this trend remains unconfirmed. This trend is compatible with a perturbation by a planet of less than 12 Earth masses on an orbit within about 0.08 AU of the star.[14] This is still unconfirmed.[15]
References
- ^ a b c d e f g h i j k l "Query Result:LHS 310 -- High proper-motion Star". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=LHS+310. Retrieved 2007-11-28.
- ^ a b c d e f g h Butler, R. Paul et al. (2004). "A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436". The Astrophysical Journal 617 (1): 580–588. arXiv:astro-ph/0408587. Bibcode 2004ApJ...617..580B. doi:10.1086/425173. http://www.iop.org/EJ/article/0004-637X/617/1/580/60944.html. Retrieved 2009-12-26.
- ^ a b c Johnson, H. M.; Wright, C. D. (1983). "Predicted infrared brightness of stars within 25 parsecs of the sun" (abstract). Astrophysical Journal Supplement Series 53: 643–711. Bibcode 1983ApJS...53..643J. doi:10.1086/190905.—see page 673.
- ^ a b Bean, Jacob L.; Benedict, G. Fritz; Endl, Michael (2006). "Metallicities of M Dwarf Planet Hosts from Spectral Synthesis" (abstract). The Astrophysical Journal 653 (1): L65–L68. arXiv:astro-ph/0611060. Bibcode 2006ApJ...653L..65B. doi:10.1086/510527.—for the metallicity, note that
or 44% - ^ Saffe, C.; Gómez, M.; Chavero, C. (2006). "On the Ages of Exoplanet Host Stars". Astronomy & Astrophysics 443 (2): 609–626. arXiv:astro-ph/0510092. Bibcode 2005A&A...443..609S. doi:10.1051/0004-6361:20053452.
- ^ Gillon, M. et al. (2007). "Detection of transits of the nearby hot Neptune GJ 436 b". Astronomy and Astrophysics 472 (2): L13–L16. Bibcode 2007A&A...472L..13G. doi:10.1051/0004-6361:20077799.
- ^ Deming, D. et al. (2007). "Spitzer Transit and Secondary Eclipse Photometry of GJ 436b". The Astrophysical Journal 667 (2): L199–L202. Bibcode 2007ApJ...667L.199D. doi:10.1086/522496.
- ^ Ribas, I.; Font-Ribera, S. and Beaulieu, J. P. (2008). "A ~5 M⊙ Super-Earth Orbiting GJ 436?: The Power of Near-Grazing Transits". The Astrophysical Journal 677 (1): L59–L62. Bibcode 2008ApJ...677L..59R. doi:10.1086/587961.
- ^ a b Reuters
- ^ "New Super-Earth is Smallest Yet". Space.com. http://www.space.com/scienceastronomy/080409-smallest-exoplanet.html. Retrieved 2008-04-10.
- ^ Alonso, R. et al. (2008). "Limits to the planet candidate GJ 436c". Astronomy and Astrophysics 487 (1): L5–L8. Bibcode 2008A&A...487L...5A. doi:10.1051/0004-6361:200810007.
- ^ Schneider, J.. "Notes for star GJ 436". The Extrasolar Planets Encyclopaedia. http://exoplanet.eu/star.php?st=GJ+436. Retrieved 2008-09-07.
- ^ Bean, J. L. and Seifahrt, A. (2008). "Observational Consequences of the Recently Proposed Super-Earth Orbiting GJ436". Astronomy and Astrophysics 487 (2): L25–L28. Bibcode 2008A&A...487L..25B. doi:10.1051/0004-6361:200810278.
- ^ Coughlin, J. L. et al. (2008). "New Observations and a Possible Detection of Parameter Variations in the Transits of Gliese 436b". The Astrophysical Journal 689 (2): L149–L152. Bibcode 2008ApJ...689L.149C. doi:10.1086/595822.
- ^ Pont et al.; Gilliland, R. L.; Knutson, H.; Holman, M.; Charbonneau, D. (2008). "Transit infrared spectroscopy of the hot Neptune around GJ 436 with the Hubble Space Telescope". Monthly Notices of the Royal Astronomical Society Letters 393 (1): L6–L10. Bibcode 2009MNRAS.393L...6P. doi:10.1111/j.1745-3933.2008.00582.x.
External links
- "Gliese 436 / AC+27 28217". SolStation company. http://www.solstation.com/stars2/gl436.htm. Retrieved 2007-11-28.
- "GJ 436". Exoplanets. http://media4.obspm.fr/exoplanets/base/etoile.php?nom=GJ+436. Retrieved 2009-05-20.
Coordinates: 11h 42m 11.0941s, +26° 42′ 23.652″
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