HD 209458 b
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Exoplanet HD 209458 b |
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| Artist's impression of HD 209458 b in front of its star HD 209458 with a tail through this material discharged from the atmosphere | |
| Constellation | Pegasus |
| Position equinox : J2000.0 |
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| Right ascension | 22h 03m 10.773s |
| declination | + 18 ° 53 ′ 03.548 ″ |
| Orbit data | |
| Central star | HD 209458 |
| Major semi-axis | 0.047 AU |
| eccentricity | 0.0082 +0.0078−0.0082 |
| Period of circulation | 3.525 d |
| Further data | |
| radius | 1.38 ± 0.018 R J |
| Dimensions | 0.69 ± 0.017 M J |
| distance | 48 pc |
| Discovery method | Transit method |
| Orbit inclination | 86.59 ± 0.05 ° |
| history | |
| discovery | Henry et al. |
| Date of discovery | 1999 |
| Catalog names | |
| HD 209458 b, V376 Peg b | |
HD 209458 b is an exoplanet 160 light years from Eartharound the star HD 209458 , which is unofficiallynamed Osiris by its discoverers after the ancient Egyptian god of fertility and death.
description
The planet HD 209458 b has a mass one third less than Jupiter , but its diameter is 1.3 times larger than that of Jupiter due to the heated atmosphere due to its proximity to the central star. This results in a very low density of around 0.3 g / cm³, so that the planet cannot have a particularly large core. HD 209458 b orbits its sun-like central star HD 209458 at a distance of 6.92 million km, i.e. H. the orbit is one eighth the size of Mercury . The orbital period is only 3½ earth days, the average speed around 140 km / s, the eccentricity of the orbit is 0.07. Due to the narrow orbit and the large mass, Osiris is assigned to the class of " hot Jupiter ". Its surface temperature is at least 1000 K appreciated. Spectroscopic observations of the transit in front of the central star with the Keck telescope suggest a retrograde orbit due to the Rossiter-McLaughlin effect . In its atmosphere is water vapor detected.
Discovery story
The Earth is only 3 degrees above the orbital plane of Osiris, so HD 209458 b was the first exoplanet to be detected using the transit method in 1999 . Caused by the passing of the planet, the apparent brightness of the central star decreases by 1.6% every three and a half days for two and a half hours. The albedo of the planet itself, measured by the MOST satellite , is 30%, well below the value of the albedo of Jupiter (52%)
In 2003, with the help of the Hubble Space Telescope, it was possible to observe that the Osiris atmosphere "evaporates" due to its proximity to the central star and forms a tail, similar to a comet . Oxygen and carbon in the form of carbon dioxide and methane have been detected in the planet's atmosphere .
In April 2007, the Hubble Space Telescope detected significant amounts of water vapor in the planet's atmosphere. This makes HD 209458b the first planet outside our solar system on which water has been detected. However, the water vapor spectra could not be confirmed in subsequent investigations. The planet has an atmospheric “tail” consisting predominantly of hydrogen, which extends up to about 200,000 km (roughly equivalent to its diameter) behind it. The strong heating of the atmosphere means that HD 209458 b loses 100,000 to 500,000 tons of hydrogen per second to the surrounding space. This phenomenon has also been demonstrated for the extrasolar planet HD 189733 b . It is estimated that the planet lost around 7% of its mass in this way during its roughly 5 billion years of existence. However, the exact mechanism of hydrogen evaporation is quite complex and the loss rate may also be significantly lower than previously assumed.
With the help of the Spitzer Space Telescope , it was possible in 2005 to measure the planet's infrared radiation during a transit.
Web links
- Astronomie.de: View into the atmosphere of an exoplanet ( Memento from September 28, 2007 in the Internet Archive ) (February 1, 2007)
- Telepolis article on oxygen / carbon detection on Osiris (February 6, 2004)
- ESA press release (March 12, 2003)
- More about the discovery of water vapor (April 11, 2007)
- Yasushi Suto, Y. Ohta, A. Taruya: The Rossiter-McLaughlin effect of transiting extrasolar planetary systems (PDF; 432 kB) Modeling and data on the orbit of HD209458b - Script for IAU 9th Asian-Pacif Regional Meeting 2005. (Eng.)
- 10,000 kilometers per hour - a monstrous storm rages over distant planets. In: Spiegel online . June 24, 2010.
- RA Wittenmyer et al .: System Parameters of the Transiting Extrasolar Planet Hd 209458B. In: The Astrophysical Journal. 632, October 20, 2005, 1157Ð1167. (PDF; engl.)
literature
- T. Castellano, J. Jenkins, DE Trilling, L. Doyle, D. Koch: Detection of Planetary Transits of the Star HD 209458 in the Hipparcos Data Set. In: Astrophysical Journal . Volume 532, Issue 1, 2000, pp. L51-L53.
- D. Charbonneau : HD 209458 and the Power of the Dark Side. (= ASP Conference Series. Vol 294). Astronomical Society of the Pacific, San Francisco 2003, ISBN 1-58381-141-9 , pp. 449-456.
- JJ Fortney, D. Sudarsky, I. Hubeny, CS Cooper, WB Hubbard, A. Burrows, JI Lunine: On the Indirect Detection of Sodium in the Atmosphere of the Planetary Companion to HD 209458. In: Astrophysical Journal. Volume 589, 2003, pp. 615-622.
Individual evidence
- ↑ HD 209458b. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on January 13, 2019 .
- ↑ a b c d e f g HD 209458. In: Extrasolar Planets Encyclopaedia . Retrieved January 13, 2019 .
- ↑ V376 Peg. In: SIMBAD. Center de Données astronomiques de Strasbourg, accessed on January 13, 2019 .
- ^ NASA: Hubble Traces Subtle Signals of Water on Hazy Worlds. December 3, 2013, accessed December 7, 2013 .
- ↑ Exoplanet with organic molecules (astronews)
- ↑ TS Barman: Identification of Absorption Features in an Extrasolar Planet Atmosphere. (preprint) dated April 11, 2007.