- 18 Scorpii
Starbox begin
name = 18 Scorpii Starbox observe
epoch =J2000.0
constell =Scorpius
ra = 16h 15m 37s
dec = -08° 22' 06"
appmag_v = 5.50 Starbox character
class = G2 Va
b-v = +0.64
u-b = 0.18
variable = No Starbox astrometry
radial_v = 11
parallax = 71.30
p_error = 0.89
prop_mo_ra = -496
prop_mo_dec = 232
absmag_v = 4.77 Starbox detail
mass = 1.01 ± 0.03
radius = 1.02–1.03
metal = 104%
luminosity = 1.08
temperature = 5800
age = 4.2 × 109 |?
rotation = 23 days Starbox catalog
names = HR 6060, HD 146233, BD-07 4242, HIP 79672, SAO 141066, GC 21864, CCDM 16156-082218 Scorpii is a
star located some 45.7light year s fromEarth 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,cite journal | author = Cayrel de Strobel, G. | year = 1996 | title = Stars Resembling the Sun | journal =Astronomy & Astrophysics Review | volume =7 | issue = 3 | pages = 243–288 | doi = 10.1007/s001590050006] and Porto de Mello & da Silva (1997) identified it as asolar twin .cite journal | author = Porto de Mello, G. F., and da Silva, L. | year = 1997 | title = HR 6060: The Closest Ever Solar Twin? | journal =The Astrophysical Journal | volume =482 | issue = 2 | pages = L89–L92 | doi = 10.1086/310693 ] Some scientists therefore believe the prospects forlife in its vicinity are good.Star characteristics
18 Scorpii is a yellow
main sequence star of spectral and luminosity type G2 Va.cite journal | author = Porto de Mello, G. F., & da Silva, L. | year = 1997 | title = HR 6060: The Closest Ever Solar Twin? | journal =The Astrophysical Journal | volume =545 | issue = 2 | pages = L89–L92 | doi = 10.1086/310693] Meléndez & Ramírez (2007) found itsmetallicity to be about 1.04 times that of the Sun.cite journal | author = Meléndez, J., & Ramírez, I. | year = 2007 | title = HIP 56948: A Solar Twin with a Low Lithium Abundance | journal =The Astrophysical Journal | volume =669 | issue = 2 | pages = L89–L92 | doi = 10.1086/523942]According to Lockwood (2002), it has a temporal photometric behavior very similar to the Sun.cite journal | author = G. W. Lockwood, et al. | month = May | year = 2002 | url = http://schwab.tsuniv.edu/papers/baas/aas2002poster.pdf | format = PDF | title = Gauging the Sun: Comparative photometric and magnetic activity measurements of sunlike stars, 1984-2001 | journal = Bulletin of the American Astronomical Society | volume = 34 | pages = 651 ] Its brightness variation over its entire activity cycle is 0.09%, about the same as the Sun's brightness variations during recent solar cycles.cite journal | author = Hall, J. C., & Lockwood, G. W. | title = The Sun-Like Activity of the Solar Twin 18 Scorpii | journal = The Astronomical Journal | volume = 133 | issue = 5 | year = 2007 | pages = 2206–2008 | doi = 10.1086/513195] Using the technique of
Zeeman-Doppler imaging , Petit et al. (2008) have detected its surface magnetic field, showing that its intensity and geometry are very similar to the large-scale solar magnetic field.cite journal | author = Petit, P., Dintrans, B., et al. | title = Toroidal versus poloidal magnetic fields in Sun-like stars : a rotation threshold | journal = Monthly Notices of the Royal Astronomical Society | volume = 388 | issue = 1 | year = 2008 | pages = 80]However, 18 Scorpii's cycle is significantly shorter than the Sun's, and its overall chromospheric activity level is noticeably higher.cite journal | author = Hall, J. C., & Lockwood, G. W. | title = Evidence of a Pronounced Activity Cycle in the Solar Twin 18 Scorpii | journal = The Astrophysical Journal | volume = 545 | issue = 2 | year = 2000 | pages = L43–L45 | doi = 10.1086/317331]
18 Scorpii is a solitary star, and radial velocity measurements have not yet revealed the presence of planets orbiting it.cite journal | author = Marcy, G. W., et al. | title = Five New Extrasolar Planets | journal = The Astrophysical Journal | volume = 619 | issue = 1 | year = 2005 | pages = 570–584 | doi = 10.1086/426384]
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.Prospects for life
18 Scorpii was identified in September 2003 by astrobiologist
Margaret Turnbull from theUniversity of Arizona inTucson as one of the most promising nearby candidates for hosting life based on her analysis of theHabCat list of stars.See also
*
List of stars
*List of nearest stars
*37 Geminorum
*Planetary habitability
*Solar twin
*Space colonization
*HD 98618 References
External links
* [http://www.solstation.com/stars2/18sco.htm NASA article on 18 Scorpii]
* [http://www.stellar-database.com/Scripts/search_star.exe?Name=18+scorpii 18 Scorpii entry in the stellar database]
* [http://www.lowell.edu/media/releases.php?release=20070215 Astronomers Measure Sun-Like Brightness Changes of the Solar Twin, 18 Scorpii]
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