D. Charbonneau T. Brown David Latham M. Mayor G.W. Henry G. Marcy R.P. Butler S.S. Vogt
Discovery site
High Altitude Observatory Geneva Observatory
Discovery date
September 9, 1999
Detection method
Radial velocity
Orbital characteristics[3]
Semi-major axis
0.04707 AU (7,042,000 km)
Eccentricity
<0.0081
Orbital period (sidereal)
3.52474859(38) d 84.59396616 h
Inclination
86.710°±0.050°
Time of periastron
2452826.629283(87) JD
Argument of periastron
83[citation needed]
Semi-amplitude
84.27+0.69 −0.70 m/s
Star
HD 209458
Physical characteristics[3]
Mean radius
1.359+0.016 −0.019RJ
Mass
0.682+0.014 −0.015MJ
Mean density
0.333+0.014 −0.013 g/cm3
Surface gravity
9.2 m/s2 (0.94 g)
Albedo
0.096±0.016 (geometric)[4]
Temperature
1499±15 K (1,226 °C; 2,239 °F, dayside)[5] 972±44 K (699 °C; 1,290 °F, nightside)[5]
HD 209458 b is an exoplanet that orbits the solar analog HD 209458 in the constellation Pegasus, some 157 light-years (48 parsecs) from the Solar System. The radius of the planet's orbit is 0.047 AU (7.0 million km; 4.4 million mi), or one-eighth the radius of Mercury's orbit (0.39 AU (36 million mi; 58 million km)). This small radius results in a year that is 3.5 Earth-days long and an estimated surface temperature of about 1,000 °C (1,800 °F; 1,300 K). Its mass is 220 times that of Earth (0.69 Jupiter masses) and its volume is some 2.5 times greater than that of Jupiter. The high mass and volume of HD 209458 b indicate that it is a gas giant.
HD 209458 b represents a number of milestones in exoplanetary research. It was the first of many categories:
a transiting extrasolar planet
The first planet detected through more than one method
an extrasolar planet known to have an atmosphere
an extrasolar planet observed to have an evaporating hydrogen atmosphere
an extrasolar planet found to have an atmosphere containing the elements oxygen and carbon
one of the first two extrasolar planets to be directly observed spectroscopically
The first extrasolar gas giant to have its superstorm measured
the first planet to have its orbital speed measured, determining its mass directly.[6]
Based on the application of newer theoretical models, as of April 2007, it is thought to be the first extrasolar planet found to have water vapor in its atmosphere.[7][8][9][10]
In July 2014, NASA announced finding very dry atmospheres on HD 209458 b and two other exoplanets (HD 189733 b and WASP-12b) orbiting Sun-like stars.[11]
HD 209458 b has been nicknamed "Osiris" after the Egyptian god.[12][13] This nickname has been acknowledged by the IAU, but as of 2023[update] it has not yet been approved as an official proper name.[14]
^Cite error: The named reference Charbonneau2000 was invoked but never defined (see the help page).
^Cite error: The named reference Henry2000 was invoked but never defined (see the help page).
^ abCite error: The named reference Bonomo2017 was invoked but never defined (see the help page).
^Cite error: The named reference Brandeker2022 was invoked but never defined (see the help page).
^ abCite error: The named reference Zellem2014 was invoked but never defined (see the help page).
^Cite error: The named reference Ignas was invoked but never defined (see the help page).
^Cite error: The named reference Space.com water was invoked but never defined (see the help page).
^Signs of water seen on planet outside solar system, by Will Dunham, Reuters, Tue Apr 10, 2007 8:44PM EDT
^Cite error: The named reference NASA-20131203 was invoked but never defined (see the help page).
^Cite error: The named reference ApJ-20130910 was invoked but never defined (see the help page).
^Cite error: The named reference NASA-20140724 was invoked but never defined (see the help page).
^Cite error: The named reference Vidal-Madjar2004 was invoked but never defined (see the help page).
^Cite error: The named reference Vidal-Madjar2008 was invoked but never defined (see the help page).
^Cite error: The named reference IAUnaming was invoked but never defined (see the help page).
HD209458b is an exoplanet that orbits the solar analog HD209458 in the constellation Pegasus, some 157 light-years (48 parsecs) from the Solar System...
HD209458 is a star with an orbiting exoplanet in the constellation Pegasus. It has an apparent visual magnitude of 7.65 and an absolute magnitude of...
stars: HD 189733 b, HD209458b, and WASP-12b. On October 6, 2005, a team of astronomers announced the discovery of transiting planet HD 189733 b. The planet...
fluxes could have had their envelopes stripped by photoevaporation. HD209458b is an example of a gas giant that is in the process of having its atmosphere...
(992 °C; 1,817 °F). This is between the predicted temperatures of HD 189733 b and HD209458b (1,180 K (910 °C; 1,660 °F)–1,392 K (1,119 °C; 2,046 °F)), before...
about 1,540 K (2,310 °F; 1,270 °C) above the predicted temperature of HD209458b (1,400 K (2,100 °F; 1,100 °C)), which had inaugurated the category of...
in the past. Main article: Extraterrestrial atmosphere Atmosphere of HD209458b The circulation of the atmosphere occurs due to thermal differences when...
optical and near-infrared wavelengths. In 2014, a magnetic field around HD209458b was inferred from the way hydrogen was evaporating from the planet. It...
HD209458b, XO-1b, WASP-12b, WASP-17b, and WASP-19b. In July 2014, NASA announced finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b...
discoveries did not come until the 2010s. In 2014, a magnetic field around HD209458b was inferred from the way hydrogen was evaporating from the planet. In...
layers Extrasolar planet atmospheres: including those of HD 189733 b and HD209458b, Tau Boötis b, HAT-P-11b, XO-1b, WASP-12b, WASP-17b, and WASP-19b. Stellar...
Jonathan (2014-07-02). "The 4.5 μm full-orbit phase curve of the hot Jupiter HD 209458b". The Astrophysical Journal. 790 (1): 53. arXiv:1405.5923. Bibcode:2014ApJ...
November 27 – A hydrogen atmosphere is discovered on the extrasolar planet HD209458b, nicknamed Osiris, by the Hubble Space Telescope. It is the first atmosphere...
water absorption in the atmosphere of HD209458b. A planet about 150 light years away from earth, HD209458b was known previously to contain an evaporating...
dwarfs. For example, the extrasolar planet HD209458b has a mass of 0.69 MJ, while the brown dwarf Gliese 229 b has a mass of 60.4 MJ. Theoretical models...
atmosphere effects. The actual temperature from spectroscopic analysis for HD209458b (Osiris) is 1,130 K, but the effective temperature is 1,359 K.[citation...
uplifted in the wake of the meteorite impact 9.8 billion years (4 Gya): HD209458b, first planet detected through its transit, forms. Messier 85, lenticular...
Nicolas B. Cowan; Adam P. Showman; Curtis S. Cooper; S. Thomas Megeath (10 May 2007). "A map of the day–night contrast of the extrasolar planet HD 189733b"...
substantial, approximately 500 K (227 °C; 440 °F) for a model based on HD209458b. They appear to be more common around F- and G-type stars and less so...
Cheetham, A.; de Wit, W. J.; Norris, B.; Olguin, F. A.; Tuthill, P. (December 2017). "The protoplanetary system HD 100546 in H α polarized light from SPHERE/ZIMPOL:...
March 2017. "HD209458b". Extrasolar Planets Encyclopaedia. Archived from the original on 2010-01-16. Retrieved 2010-02-16. "Planet CoRoT-7 b". Extrasolar...
planetary transit observed (by already known exoplanet) was caused by HD209458b. The most massive transiting exoplanet is KELT-1b which masses 27.23...
Global Information