HD 188753

Starbox begin
name = HD 188753 Starbox image


caption = HD 188753 on DSS2 sky survey 0.4° view Starbox observe
epoch = J2000.0
constell = Cygnus
ra = RA|19|54|58.37
dec = DEC|+41|52|17.5
appmag_v = +7.43Starbox character
class = GV / K0V / MV
r-i =
v-r =
b-v =
u-b = Starbox astrometry
radial_v = -23.5
prop_mo_ra = -52.76
prop_mo_dec = 284.44
parallax = 22.31
p_error = 0.78
dist_ly = 149
dist_pc = 46
absmag_v = 4.17Starbox visbin
primary = HD 188753 A
name = HD 188753 BC
period = 25.7
axis =
axis_unitless = 12.3 AU
eccentricity = 0.5
inclination =
node =
periastron =
periarg = Starbox detail
mass = 1.06
radius = 1.28
gravity =
luminosity = 1.6
temperature = 5750
age = 5600 millionStarbox catalog
names = ADS 13125, BD+41 3535, HIP 98001, HO 581, SAO 48968, WDS 19550+4152Starbox reference
Simbad = HD+188753

HD 188753 is a triple star system approximately 149 light-years away in the constellation of Cygnus (the Swan). In 2005, an extrasolar planet was announced to be orbiting the primary star (designated HD 188753 A) in the system. However, follow-up measurements did not confirm the planet's existence and questioned whether the original data supported the planet hypothesis in the first place.

Stellar components

The primary star, HD 188753 A, is a Solar twin, yellow dwarf star with an unsure spectral type. It is calculated that the star has a mass that is greater than the Sun's, a larger radius, and a brighter luminosity. Because of its temperature, scientists believe that the star is approximately 5600 million years old.

Orbiting this at a distance separated from the primary star at approximately midway between the Sun-Saturn and Sun-Uranus distance: 12.3 AU, are two stars orbiting each other. These have a total mass of 1.63 solar masses and orbit the primary with an eccentricity of 0.50 (an earlier estimate put the eccentricity at 0.26±0.07 [ [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1978Obs....98..122B&db_key=AST&data_type=HTML&format= On the circularity of orbit of certain spectroscopic binaries ] ] ).

The secondary (HD 188753 B) has a spectral class of K0 (orange dwarf), and its companion (HD 188753 C) is an M2-type (red dwarf). These orbit each other in 156 days, and the primary in 25.7 years.

Disproven planet

In 2005 the discovery of a planet orbiting the primary star of the triple star system was announced. The planet, which received the designation HD 188753 Ab, was announced by a Polish astronomer working in the United States, Dr. Maciej Konacki. [ [http://www.nature.com/news/2005/050711/full/050711-6.html Access : The triple sunset that should not exist : Nature News ] ] This planet was not the first known planet in a triple star system - for example, the planet 16 Cygni Bb had been discovered earlier, orbiting one of the components of a wide triple system also in the constellation of Cygnus.

Since HD 188753 Ab was orbiting in a multi-star system, Konacki referred to planets of this type as "Tatooine planets" after Luke Skywalker's home world. [ [http://mr.caltech.edu/media/Press_Releases/PR12716.html Caltech Press Release, 7/13/2005, Dr. Maciej Konacki ] ] The detection of this planet has been challenged by Eggenberger et al. [http://www.ncac.torun.pl/~maciej/Planets/HD188753Ab.html Maciej Konacki, Home Page ] ] [ [http://arxiv.org/abs/astro-ph/0702574 [astro-ph/0702574 No evidence of a hot Jupiter around HD 188753 A ] ]

The planet, a Hot Jupiter gas giant slightly more massive than Jupiter, was thought to orbit the star HD 188753 A once every 80 hours or so (3.3 days), at a distance of about 8 gigameters, a twentieth of the distance between Earth and the Sun. The existence of HD 188753 Ab (a hot Jupiter) in a relatively close triple star system challenged the current models of planet formation. The current idea is that giant planets form in the outer reaches of their system (in similar orbits as Jupiter and Saturn). Once formed, some of these planets may migrate close to their stars, becoming hot Jupiters. The issue with HD 188753 Ab is that any protoplanetary disk would have been ended around 1 astronomical unit from the primary star (due to the presence of the secondary stars). A Jovian planet should not have been able to form so close to the primary, and with no disk material beyond 1 AU, a planet should not have been able to form beyond that distance to migrate inward. [ cite journal | author=Hatzes AP, Wuchterl G | title=Astronomy: giant planet seeks nursery place | journal=Nature | volume=436 | issue=7048 | year=2005 | pages=182–3 | pmid=16015311 | doi=10.1038/436182a] One of the possibilities suggested that the planet formed before the secondary stars had reached their current configuration. This suggests that the two secondary stars were once more distant than they are now.

However, an attempt to confirm the discovery failed. In 2007, a team at the Geneva Observatory concluded that the claimed planet does not exist and that the data provided in the original discovery paper did not support the existence of the proposed planet either. [ [http://arxiv.org/abs/astro-ph/0702574 No evidence of a hot Jupiter around HD 188753 A ] ] Konacki issued a response to this, claiming that the precision of the follow-up measurements was not in fact sufficient to confirm or deny the planet's existence and that he planned to release an update in 2007, though as of 2008 no update has been published.

See also

* 51 Pegasi
* Alpha Centauri
* Polaris
* Rizq

References

External links

* [http://www.extrasolar.net/startour.asp?StarCatId=&StarId=257 HD 188753 A] , [http://www.extrasolar.net/startour.asp?StarCatId=&StarId=258 B] , and [http://www.extrasolar.net/startour.asp?StarCatId=&StarId=259 C] . "Extrasolar Visions". Retrieved on 2008-06-23.
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