HD 209458

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HD 209458
Pegasus constellation map.svg
Cercle rouge 100%25.svg
HD 209458 (100x100)

HD 209458 (circled) in the constellation Pegasus.
Observation data
Epoch J2000       Equinox J2000
Constellation Pegasus
Right ascension 22h 03m 10.77275s [1]
Declination +18° 53′ 03.5494″ [1]
Apparent magnitude  (V)7.65 [2]
Characteristics
Evolutionary stage main sequence
Spectral type F9 V [3] or G0 V [4]
Apparent magnitude  (B)8.244 [2]
Apparent magnitude  (K)6.308±0.026 [2]
B−V color index +0.574±0.014 [5]
Variable type EP [6]
Astrometry
Radial velocity (Rv)−14.78±0.16 [1]  km/s
Proper motion (μ)RA: 29.766(28)  mas/yr [1]
Dec.: −17.976(25)  mas/yr [1]
Parallax (π)20.7694 ± 0.0266  mas [1]
Distance 157.0 ± 0.2  ly
(48.15 ± 0.06  pc)
Absolute magnitude  (MV)4.28±0.10 [5]
Details
Mass 1.148±0.022 [7]   M☉
Radius 1.203±0.061 [7]   R☉
Luminosity 1.77±0.14 [7]   L☉
Temperature 6071±20 [7]   K
Metallicity [Fe/H]0.00±0.02 [5]   dex
Rotation 14.4 days[ citation needed ]
Rotational velocity (v sin i)4.228±0.007 [8]  km/s
Age 3.5±1.4 [7]   Gyr
Other designations
V376 Peg, BD+18°4917, HIP  108859, SAO  107623, 2MASS J22031077+1853036 [9]
Database references
SIMBAD data
Exoplanet Archive data
Extrasolar Planets
Encyclopaedia 		data
HD 209458 (center) HD209458.jpg
HD 209458 (center)

HD 209458 is a star with an orbiting exoplanet in the constellation Pegasus. It has an apparent visual magnitude of 7.65 [2] and an absolute magnitude of 4.28. [5] Because it is located at a distance of 157 light-years (48 parsecs ) from the Sun as measured via parallax, it is not visible to the unaided eye. With good binoculars or a small telescope it should be easily detectable. The system is drifting closer with a heliocentric radial velocity of −14.8 km/s. [1]

Contents

The spectrum of HD 209458 presents as a late F- or early G-type main-sequence star with a stellar classification of F9 V [3] or G0 V, [4] respectively. It is roughly 3.5 [7]  billion years old and is spinning with a projected rotational velocity of 4.2 km/s. [8] The star displays a moderate amount of magnetic activity in its chromosphere. [10] It has a 15% greater mass than the Sun and a 20% larger radius. The abundance of iron, a measure of the metallicity of the star, is solar. [7] HD 209458 is radiating 1.8 times the luminosity of the Sun from its photosphere at an effective temperature of 6,071 K. [7]

Because the planet transits the star, the star is dimmed by about 2% every 3.5 days making it an extrinsic variable. The variable star designation for HD 209458 is V376 Pegasi. It is the prototype of the variable class "EP" in the General Catalogue of Variable Stars, defined as stars showing eclipses by their planets. [6] [11]

Planetary system

A light curve of planet HD 209458 b transiting the star, adapted from Brown et al. (2001) V376PegLightCurve.png
A light curve of planet HD 209458 b transiting the star, adapted from Brown et al. (2001)

In 1999, two teams working independently (one team consisted of astronomers at the Geneva Observatory, the Center for Astrophysics | Harvard & Smithsonian, and the Wise Observatory; the second group was the California and Carnegie Planet Search team) discovered an extrasolar planet orbiting the star by using the radial velocity planet search method. Soon after the discovery, separate teams led by David Charbonneau and Gregory W. Henry were able to detect a transit of the planet across the surface of the star making it the first known transiting extrasolar planet. [4] [13] The planet received the designation HD 209458 b.

The planet is now under even more public scrutiny with the announcement that its atmosphere contains water vapor. Astronomers had made careful photometric measurements of several stars known to be orbited by planets, in the hope that they might observe a dip in brightness caused by the transit of the planet across the star's face. This would require the planet's orbit to be inclined such that it would pass between the Earth and the star, and previously no transits had been detected.

Travis Barman at Lowell Observatory in Flagstaff, Arizona analyzed the emission spectrum of this planet in 2007, and believes that its atmosphere contains water vapor, [14] although previous research in 2007 [15] suggests that the atmosphere is composed mostly of silicate clouds. A spectrum taken in 2020 detected either sodium or titanium oxide in the planet's atmosphere. [16] A later study in 2021 did not find any molecular absorption features in the planetary atmosphere at all. [17]

The HD 209458 planetary system [8]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 0.682+0.014
−0.015  MJ 		0.04707+0.00045
−0.00047		3.52474859(38)<0.008186.71±0.05 ° 1.359+0.016
−0.019  RJ

See also

Related Research Articles

<span class="mw-page-title-main">HD 209458 b</span> Gas giant exoplanet orbiting HD 209458

HD 209458 b is an exoplanet that orbits the solar analog HD 209458 in the constellation Pegasus, some 157 light-years from the Solar System. The radius of the planet's orbit is 0.047 AU, or one-eighth the radius of Mercury's orbit. This small radius results in a year that is 3.5 Earth-days long and an estimated surface temperature of about 1,000 °C. Its mass is 220 times that of Earth 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.

<span class="mw-page-title-main">Gliese 876</span> Star in the constellation Aquarius

Gliese 876 is a red dwarf star 15.2 light-years away from Earth in the constellation of Aquarius. It is one of the closest known stars to the Sun confirmed to possess a planetary system with more than two planets, after GJ 1061, YZ Ceti, Tau Ceti, and Wolf 1061; as of 2018, four extrasolar planets have been found to orbit the star. The planetary system is also notable for the orbital properties of its planets. It is the only known system of orbital companions to exhibit a near-triple conjunction in the rare phenomenon of Laplace resonance. It is also the first extrasolar system around a normal star with measured coplanarity. While planets b and c are located in the system's habitable zone, they are giant planets believed to be analogous to Jupiter.

HD 74156 is a yellow dwarf star in the constellation of Hydra, 187 light years from the Solar System. It is known to be orbited by two giant planets.

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<span class="mw-page-title-main">HD 187123</span> Star in the constellation Cygnus

HD 187123 is a single, yellow-hued star with two exoplanetary companions in the northern constellation of Cygnus. It has an apparent visual magnitude of 7.83, making it an 8th magnitude star that is too faint to be visible with the naked eye. However, it should be easy target with binoculars or small telescope. The system is located at a distance of 150 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −17 km/s.

<span class="mw-page-title-main">HD 192263</span> Star in the constellation Aquila

HD 192263 is a star with an orbiting exoplanet in the equatorial constellation of Aquila. The system is located at a distance of 64 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of −10.7 km/s. It has an absolute magnitude of 6.36, but at that distance the apparent visual magnitude is 7.79. It is too faint to be viewed with the naked eye, but with good binoculars or small telescope it should be easy to spot.

HD 114729 is a Sun-like star with an orbiting exoplanet in the southern constellation of Centaurus. Based on parallax measurements, it is located at a distance of 124 light years from the Sun. It is near the lower limit of visibility to the naked eye, having an apparent visual magnitude of 6.68 The system is drifting further away with a heliocentric radial velocity of 26.3 km/s. The system has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.373″·yr−1.

HD 179949 is a 6th magnitude star in the constellation of Sagittarius. It is a yellow-white dwarf, a type of star hotter and more luminous than the Sun. The star is located about 90 light years from Earth and might be visible under exceptionally good conditions to an experienced observer without technical aid; usually binoculars are needed.

HD 130322 is a star with a close orbiting exoplanet in the constellation of Virgo. The distance to this system is 104 light years, as determined using parallax measurements. It is drifting closer to the Sun with a radial velocity of −12.4 km/s. With an apparent visual magnitude of 8.04, it is too dim to be visible to the naked eye; requiring binoculars or a small telescope to view. Being almost exactly on the celestial equator the star is visible everywhere in the world except for the North Pole. The star shows a high proper motion, traversing the celestial sphere at an angular rate of 0.197 arcsec yr−1.

<span class="mw-page-title-main">HD 189733</span> Binary star system in the constellation Vulpecula

HD 189733, also catalogued as V452 Vulpeculae, is a binary star system 64.5 light-years away in the constellation of Vulpecula. The primary star is suspected to be an orange dwarf star, while the secondary star is a red dwarf star. 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).

HD 38529 is a binary star approximately 138 light-years away in the constellation of Orion.

HD 224693, also named Axólotl, is a star in the equatorial constellation of Cetus, and is positioned near the western constellation border with Aquarius. It can be viewed with a small telescope but is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.23. Based on parallax measurements, the object is located at a distance of approximately 306 light years from the Sun. It is drifting further away with a radial velocity of 1.5 km/s.

<span class="mw-page-title-main">XO-1b</span> Extrasolar planet in the constellation Corona Borealis

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<span class="mw-page-title-main">HAT-P-2b</span> Extrasolar planet

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<span class="mw-page-title-main">HD 189733 b</span> Hot Jupiter exoplanet in the constellation Vulpecula

HD 189733 b is an exoplanet in the constellation of Vulpecula approximately 64.5 light-years away from our Solar System. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 11.2% higher than that of Jupiter and a radius 11.4% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.0 kilometers per second, making it a hot Jupiter with poor prospects for extraterrestrial life.

HD 114762 b is a small red dwarf star, in the HD 114762 system, formerly thought to be a massive gaseous extrasolar planet, approximately 126 light-years (38.6 pc) away in the constellation of Coma Berenices. This optically undetected companion to the late F-type main-sequence star HD 114762 was discovered in 1989 by Latham, et al., and confirmed in an October 1991 paper by Cochran, et al. It was thought to be the first discovered exoplanet

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<span class="mw-page-title-main">Discoveries of exoplanets</span> Detecting planets located outside the Solar System

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References

  1. 1 2 3 4 5 6 7 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 3 4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv: 1108.4971 . Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID   119257644.
  3. 1 2 Gray, R. O.; et al. (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars". The Astronomical Journal. 121 (4): 2148. Bibcode:2001AJ....121.2148G. doi:10.1086/319956. S2CID   117076031.
  4. 1 2 3 Charbonneau, David; et al. (2000). "Detection of Planetary Transits Across a Sun-like Star". The Astrophysical Journal Letters. 529 (1): L45–L48. arXiv: astro-ph/9911436 . Bibcode:2000ApJ...529L..45C. doi:10.1086/312457. PMID   10615033. S2CID   16152423.
  5. 1 2 3 4 Mazeh, Tsevi; et al. (2000). "The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458". The Astrophysical Journal. 532 (1): L55–L58. arXiv: astro-ph/0001284 . Bibcode:2000ApJ...532L..55M. doi:10.1086/312558. PMID   10702131. S2CID   6139784.
  6. 1 2 "GCVS query result: V376 Peg". General Catalog of Variable Stars . Sternberg Astronomical Institute, Moscow, Russia. Retrieved 2009-05-17.
  7. 1 2 3 4 5 6 7 8 Del Burgo, C.; Allende Prieto, C. (2016). "Accurate parameters for HD 209458 and its planet from HST spectrophotometry". Monthly Notices of the Royal Astronomical Society. 463 (2): 1400–1408. arXiv: 1703.01449 . Bibcode:2016MNRAS.463.1400D. doi:10.1093/mnras/stw2005. S2CID   119244708.
  8. 1 2 3 Bonomo, A. S.; et al. (June 2017). "The GAPS Programme with HARPS-N at TNG. XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets". Astronomy & Astrophysics . 602: A107. arXiv: 1704.00373 . Bibcode:2017A&A...602A.107B. doi:10.1051/0004-6361/201629882.
  9. ↑ "HD 209458". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2009-05-17.
  10. ↑ Ben-Jaffel, Lotfi (December 2007). "Exoplanet HD 209458b: Inflated Hydrogen Atmosphere but No Sign of Evaporation". The Astrophysical Journal. 671 (1): L61–L64. arXiv: 0711.1432 . Bibcode:2007ApJ...671L..61B. doi:10.1086/524706.
  11. ↑ Samus, N. N. (2009). "GCVS Variability Types and Distribution Statistics of Designated Variable Stars According to their Types of Variability" . Retrieved 2010-08-02.
  12. ↑ Brown, Timothy M.; et al. (May 2001). "Hubble Space Telescope Time-Series Photometry of the Transiting Planet of HD 209458". The Astrophysical Journal. 552 (2): 699–709. arXiv: astro-ph/0101336 . Bibcode:2001ApJ...552..699B. doi:10.1086/320580. S2CID   51819558.
  13. ↑ "Astronomers witness silhouette of planet crossing distant star" (Press release). Kamuela, Hawaii: W. M. Keck Observatory. November 7, 1999. Retrieved August 13, 2019.
  14. ↑ Barman, T. (2007). "Identification of Absorption Features in an Extrasolar Planet Atmosphere". The Astrophysical Journal Letters. 661 (2): L191–L194. arXiv: 0704.1114 . Bibcode:2007ApJ...661L.191B. doi:10.1086/518736. S2CID   13964464.
  15. ↑ Richardson, L. J.; et al. (2007). "A spectrum of an extrasolar planet". Nature. 445 (7130): 892–895. arXiv: astro-ph/0702507 . Bibcode:2007Natur.445..892R. doi:10.1038/nature05636. PMID   17314975. S2CID   4415500.
  16. ↑ Santos, N. C.; et al. (2020). "Broadband transmission spectroscopy of HD 209458b with ESPRESSO: Evidence for Na, TiO, or both". Astronomy & Astrophysics. 644: A51. arXiv: 2011.03746 . Bibcode:2020A&A...644A..51S. doi:10.1051/0004-6361/202039454. S2CID   226281853.
  17. ↑ Casasayas-Barris, N.; et al. (2021). "The atmosphere of HD 209458b seen with ESPRESSO". Astronomy & Astrophysics. 647: A26. arXiv: 2101.04094 . Bibcode:2021A&A...647A..26C. doi:10.1051/0004-6361/202039539. S2CID   231573096.
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