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HD 189733

HD 189733, also catalogued as V452 Vulpeculae, is a binary star system approximately 63 light-years away in the constellation of Vulpecula (the Fox). The primary star is suspected to be an orange dwarf star,[1] while the secondary star is a red dwarf star.[3] Given that this system has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula (M27).

As of 2005, it has been confirmed that an extrasolar planet orbits the primary star within the system.[6]


Stellar system

HD 189733 A is an orange dwarf star of the spectral type K1.5V. The star has a mass of 82 percent that of the Sun, a radius 75 percent, and a luminosity of 26.4 percent. The star is between 89 and 102 percent as enriched in iron as the Sun, making the star more than 600 million years old.

The star has starspots which affect its luminosity by 1.5 percent in visible light.[7] As a result, it is listed in the General Catalogue of Variable Stars as a BY Draconis variable with the variable star designation V452 Vul.[4]

Discovered in 2006 by the infrared 2MASS astronomical survey, 2MASS J20004297+2242342 or HD 189733 B is a dim red dwarf star of spectral type M. The companion was observed at a separation of 216 astronomical units away from the primary star. Orbiting in a clockwise orbit (which is nearly perpendicular to the orbital plane of transiting planet HD 189733 b), the orbital period is estimated around 3,200 years long.[8]

Planetary system
Planet HD 189733 (A)b orbiting star HD 189733 A

HD 189733 A has one known planet, designated HD 189733 b, a gaseous giant 13% larger than Jupiter close enough to complete an orbit every two days. Using spectrometry it was found in 2007 that this planet contains significant amounts of water vapour. This planet is the second extrasolar planet where definitive evidence for water has been found.[9]

The chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above 1,000 °C (1,830 °F) is far from being habitable, this finding increases the likelihood that water, an essential component of life, would be found on a more Earth-like planet in the future.[10]

Astronomers have created a rough map of HD 189733b's cloud-top features using data from the Spitzer infrared space telescope.

Although Spitzer could not resolve the planet into a disk, by measuring changes as the planet rotated, the team created a simple longitudinal map. That is, they measured the planet's brightness in a series of pole-to-pole strips across the planet's visible cloud-tops, then assembled those strips into an overall picture.

Probably due to strong winds, the hottest point on the planet seems to be "offset by about 30 degrees longitudinally" from the substellar point ("high noon").[11]

In late 2008, the spectral signature of carbon dioxide was found in HD 189733b's atmosphere.[12]
The HD 189733 system Companion
(in order from star) Mass Semimajor axis
(AU) Orbital period
(days) Eccentricity
b 1.13 ± 0.03 MJ 0.03099 ± 0.0006 2.21857 ± 0.00002 0.0010 ± 0.0002

See also

* List of extrasolar planets
* 2MASS The Two Micron All-Sky Survey
* ELODIE spectrograph


References

1. ^ a b c d e f g h i j k "SIMBAD query result: V* V452 Vul -- Variable of BY Dra type". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+189733. Retrieved 2009-05-22.
2. ^ a b c d e van Leeuwen, F. (2007). "HIP 98505". Hipparcos, the New Reduction. http://webviz.u-strasbg.fr/viz-bin/VizieR-5?-out.add=.&-source=I/311/hip2&recno=98174. Retrieved 2009-12-08.
3. ^ a b c d e f g h "SIMBAD query result: 2MASS J20004297+2242342 -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=2MASS+J20004297+2242342. Retrieved 2009-05-22.
4. ^ a b "GCVS query result: V452 Vul". General Catalog of Variable Stars. Sternberg Astronomical Institute, Moscow, Russia. http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=V452+Vul. Retrieved 2009-05-22.
5. ^ a b Gerard T. van Belle and Kaspar von Braun (2009). "Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars" (abstract). The Astrophysical Journal 694 (2): 1085–1098. doi:10.1088/0004-637X/694/2/1085. http://www.iop.org/EJ/abstract/0004-637X/694/2/1085/. (web Preprint)
6. ^ Bouchy et al. (2005). "ELODIE metallicity-biased search for transiting Hot Jupiters II. A very hot Jupiter transiting the bright K star HD 189733". Astronomy and Astrophysics 444: L15–L19. http://www.aanda.org/articles/aa/full/2005/46/aahi291/aahi291.html.
7. ^ Winn, J. N. et al. (2007). "The Transit Light Curve Project. V. System parameters and stellar rotation period of HD 189733". The Astronomical Journal 133 (4): 1828–1835. doi:10.1086/512159. http://www.iop.org/EJ/article/1538-3881/133/4/1828/205718.html.
8. ^ Bakos et al.; Pál, András; Latham, David W.; Noyes, Robert W.; Stefanik, Robert P. (2006). "A Stellar Companion in the HD 189733 System with a Known Transiting Extrasolar Planet". The Astrophysical Journal Letters 641 (1): L57–L60. doi:10.1086/503671. http://www.iop.org/EJ/article/1538-4357/641/1/L57/20339.html.
9. ^ "Water vapour found on exoplanet". BBC News. 2007-07-11. http://news.bbc.co.uk/1/hi/sci/tech/6292076.stm. Retrieved 2007-07-12.
10. ^ "'Clear Signs of Water' on Distant Planet". 2007-07-11. http://www.space.com/scienceastronomy/070711_water_planet.html. Retrieved 2008-02-02.
11. ^ "CfA Press Release - First Map of an Extrasolar Planet". 2007-05-09. http://www.cfa.harvard.edu/press/2007/pr200713.html. Retrieved 2008-12-06.
12. ^ "Carbon dioxide discovered on distant planet". Nature News. 2008-11-25. http://www.nature.com/news/2008/081121/full/news.2008.1248.html. Retrieved 2008-11-25.


External links

* "HD 189733 / V452 Vul / BD+22 3887 AB". SolStation. http://www.solstation.com/stars2/hd189733.htm. Retrieved 2008-06-21.
* "Where is HD 189733?". NASA. Astronomy Picture of the Day. 2008-03-21. http://apod.nasa.gov/apod/ap080321.html. Retrieved 2008-06-21.
* "HD 189733". Exoplanets. http://media4.obspm.fr/exoplanets/base/etoile.php?nom=HD+189733. Retrieved 2009-05-22.

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