HD 155358
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| Observation data Epoch J2000 |
|
|---|---|
| Constellation (pronunciation) |
Hercules |
| Right ascension | 17h 09m 34.6168s[1] |
| Declination | +33° 21′ 21.078″[1] |
| Apparent magnitude (V) | 7.5 |
| Characteristics | |
| Spectral type | G0[1] |
| Astrometry | |
| Radial velocity (Rv) | -9.1 km/s |
| Proper motion (μ) | RA: -223.50 mas/yr Dec.: -216.77 mas/yr |
| Parallax (π) | 23.04 ± 0.69[1] mas |
| Distance | 142 ± 4 ly (43 ± 1 pc) |
| Details | |
| Mass | 0.89[2] M☉ |
| Surface gravity (log g) | 4.19[1] |
| Temperature | 5,868[1] K |
| Metallicity | 21% solar[3] |
| Age | 11.9 Gyr[2] years |
| Other designations | |
HD 155358 is a low metalicity yellow dwarf star, which is known to be orbited by two extrasolar planets.[3] The two planets gravitationally interact: modelling the planets assuming their masses are the same as the empirically-determined lower limits, they exchange eccentricities on a timescale of 2700 years, and their arguments of periastron precess on a timescale of 2300 years.[3]
The star is 11.9 billion years old and has a mass 0.89 times that of the Sun.[2] It is notable for being the lowest metallicity planet-bearing star known, with an iron-to-hydrogen ratio 21% of the solar value.[3] These two planets around this star were both announced on May 10, 2007.
Contents |
[edit] Observation
With a visual magnitude of 7.5, this star can not be observed with the unaided eye. Hence it was discovered only after the introduction of the telescope. In 1859 it was catalogued in the Bonner Durchmusterung by the Prussian astronomer F. W. Argelander, who listed an estimated visual magnitude of 7.2.[4] In 1958 it was identified as a star with a relatively large proper motion by the Nizamiah Observatory, Hyderabad.[5] It was suggested in 1979 that this star may lie within 25 parsecs of the Sun. (Up to that time it had never been catalogued as a nearby star.)[6]
Beginning in 2001, this star underwent observation using the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. Changes were observed in the radial velocity motion of the star, indicating a gravitational influence from orbiting objects. Based on the motion of the star over time, astronomers were able to deduce that there are at least two planets in orbit around HD 155358.[7]
[edit] Planetary system
[edit] HD 155358 b
| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
| Orbital elements | ||
| Semimajor axis | (a) | 0.628±0.02 AU |
| Eccentricity | (e) | 0.112±0.037 |
| Orbital period | (P) | 195±1.1 d |
| Angular distance | (θ) | 14.707 mas |
| Longitude of periastron |
(ω) | 162±20° |
| Time of periastron | (T0) | 2,453,950 ±10.4 JD |
| Semi-amplitude | (K) | 34.6±3 m/s |
| Physical characteristics | ||
| Mass | (m) | >0.89 MJ |
| Discovery information | ||
| Discovery date | May 10, 2007 | |
| Discoverer(s) | Cochran et al. | |
| Detection method | Radial velocity | |
| Discovery status | Published | |
HD 155358 b is a gas giant planet that orbits the star HD 155358. This planet orbits at a distance about 63% of distance between Earth and the Sun and has a moderate eccentricity. The planet mass is 89% of Jupiter, though, only a minimum mass is known, and this planet may be more massive than Jupiter, depending on inclination of the orbit and true mass of the star (component A). It takes over half a year to orbit the star.
[edit] HD 155358 c
| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
| Orbital elements | ||
| Semimajor axis | (a) | 1.224±0.081 AU |
| Eccentricity | (e) | 0.176±0.174 |
| Orbital period | (P) | 530.3±27.2 d |
| Angular distance | (θ) | 28.665 mas |
| Longitude of periastron |
(ω) | 279±38° |
| Time of periastron | (T0) | 2,454,420.3 ±79.3 JD |
| Semi-amplitude | (K) | 14.1±1.6 m/s |
| Physical characteristics | ||
| Mass | (m) | >0.504 MJ |
| Discovery information | ||
| Discovery date | May 10, 2007 | |
| Discoverer(s) | Cochran et al. | |
| Detection method | Radial velocity | |
| Discovery status | Published | |
HD 155358 c is a gas giant planet that orbits at 1.224 AU and takes 530.3 days to orbit HD 155358. This planet orbits in an eccentric orbit. This planet has at least half of the mass of Jupiter.
[edit] References
- ^ a b c d e f g Results for HD 155358. SIMBAD Astronomical Database. Centre de Données astronomiques de Strasbourg. Retrieved on 2007-09-04.
- ^ a b c Nordstrom B., Mayor M., Andersen J., Holmberg J., Pont F., Jorgensen B.R., Olsen E.H., Udry S., Mowlavi N. (2004). The Geneva-Copenhagen Survey of Solar neighbourhood. Centre de Données astronomiques de Strasbourg. Retrieved on 2007-09-04.
- ^ a b c d Cochran, W. et al. (2007). "A Planetary System Around HD 155358: The Lowest Metallicity Planet Host Star". The Astrophysical Journal 665 (2): 1407–1412. doi:.
- ^ Argelander, Friedrich W. (1902). Bonner Durchmusterung des noerdlichen Himmels, 2nd Edition.
- ^ Goyal, A. N. (1999). "Stars with large proper motions in the astrographic zones +32° and +33° (List II)". Journal des Observateurs 41: 121.
- ^ Halliwell, M. J. (1979). "Possible nearby stars brighter than tenth magnitude". Astrophysical Journal Supplement Series 41: 173–190. doi:.
- ^ Johnson, Rebecca. "Astronomers Discover Multi-Planet System; May Alter Theories of Planet Formation", University of Texas, May 23, 2007. Retrieved on 2007-09-04.
