18 Scorpii
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| Observation data Epoch J2000.0 |
|
|---|---|
| Constellation (pronunciation) |
Scorpius |
| Right ascension | 16h 15m 37s |
| Declination | -08° 22' 06" |
| Apparent magnitude (V) | 5.50 |
| Characteristics | |
| Spectral type | G2 Va |
| U-B color index | 0.18 |
| B-V color index | +0.64 |
| Variable type | No |
| Astrometry | |
| Radial velocity (Rv) | 11 km/s |
| Proper motion (μ) | RA: -496 mas/yr Dec.: 232 mas/yr |
| Parallax (π) | 71.30 ± 0.89 mas |
| Distance | 45.7 ± 0.6 ly (14 ± 0.2 pc) |
| Absolute magnitude (MV) | 4.77 |
| Details | |
| Mass | 1.01 ± 0.03 M☉ |
| Radius | 1.02–1.03 R☉ |
| Luminosity | 1.08 L☉ |
| Temperature | 5800 K |
| Metallicity | 104% |
| Rotation | 23 days |
| Age | 4.2 × 109 years |
| Other designations | |
18 Scorpii is a star located some 45.7 light years from Earth at the northern edge of the Scorpius constellation.
18 Scorpii has many physical properties in common with the Sun. Cayrel de Strobel (1996) included it in her review of the stars most similar to the Sun,[1] and Porto de Mello & da Silva (1997) identified it as a solar twin.[2] Some scientists therefore believe the prospects for life in its vicinity are good.
Contents |
[edit] Star characteristics
18 Scorpii is a yellow main sequence star of spectral and luminosity type G2 Va.[2] Meléndez & Ramírez (2007) found its metallicity to be about 1.04 times that of the Sun.[3]
According to Lockwood (2002), it has a temporal photometric behavior very similar to the Sun.[4] Its brightness variation over its entire activity cycle is 0.09%, about the same as the Sun's brightness variations during recent solar cycles.[5] However, 18 Scorpii's cycle is significantly shorter than the Sun's, and its overall chromospheric activity level is noticeably higher.[5][6]
18 Scorpii is a solitary star, and radial velocity measurements have not yet revealed the presence of planets orbiting it.[7]
Though 18 Scorpii is only slightly more metal-rich overall than the Sun, its lithium abundance is about three times as high; for this reason, Meléndez & Ramírez (2007) have suggested that 18 Scorpii be called a "quasi solar twin", reserving the term solar twin for stars (such as HIP 56948) that match the Sun, within the observational errors, for all parameters.[3]
[edit] Prospects for life
18 Scorpii was identified in September 2003 by astrobiologist Margaret Turnbull from the University of Arizona in Tucson as one of the most promising nearby candidates for hosting life based on her analysis of the HabCat list of stars.
[edit] See also
- List of stars
- List of nearest stars
- 37 Geminorum
- Planetary habitability
- Solar twin
- Space colonization
- HD 98618
[edit] References
- ^ Cayrel de Strobel, G. (1996). "Stars Resembling the Sun". Astronomy & Astrophysics Review 7 (3): 243–288. doi:.
- ^ a b Porto de Mello, G. F., and da Silva, L. (1997). "HR 6060: The Closest Ever Solar Twin?". The Astrophysical Journal 482 (2): L89–L92. doi:.
- ^ a b Meléndez, J., & Ramírez, I. (2007). "HIP 56948: A Solar Twin with a Low Lithium Abundance". The Astrophysical Journal 669 (2): L89–L92. doi:.
- ^ G. W. Lockwood, et al. (May 2002). "Gauging the Sun: Comparative photometric and magnetic activity measurements of sunlike stars, 1984-2001" (PDF). Bulletin of the American Astronomical Society 34: 651.
- ^ a b Hall, J. C., & Lockwood, G. W. (2007). "The Sun-Like Activity of the Solar Twin 18 Scorpii". The Astronomical Journal 133 (5): 2206–2008. doi:.
- ^ Hall, J. C., & Lockwood, G. W. (2000). "Evidence of a Pronounced Activity Cycle in the Solar Twin 18 Scorpii". The Astrophysical Journal 545 (2): L43–L45. doi:.
- ^ Marcy, G. W., et al. (2005). "Five New Extrasolar Planets". The Astrophysical Journal 619 (1): 570–584. doi:.
