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COROT-7b
Extrasolar planet List of extrasolar planets
Exoplanet Comparison CoRoT-7 b.png
Size comparison of COROT-7b with Earth and Neptune.
Parent star
Star COROT-7
Constellation Monoceros
Right ascension (α) 06h 43m 49.0s[1]
Declination (δ) −01° 03′ 46.0″[1]
Apparent magnitude (mV) 11.668[1]
Distance 489 ± 65[1] ly
(150 ± 20[1] pc)
Spectral type G9V[1]
Mass (m) 0.93 ± 0.03 M☉
Radius (r) 0.87 ± 0.04 R☉
Temperature (T) 5275 ± 75 K
Metallicity [Fe/H] 0.03 ± 0.06
Age 1.2 – 2.3 Gyr
Orbital elements
Semimajor axis (a) 0.0172 ± 0.00029[1] AU
(2.58 Gm)
    0.115 mas
Eccentricity (e) 0
Orbital period (P) 0.853585 ± 0.000024[1] d
    (20.48604 h)
Inclination (i) 80.1 ± 0.3[1]°
Semi-amplitude (K) 3.3[2] m/s
Physical characteristics
Mass (m) 0.0151 ± 0.0025 MJ
(4.8 ± 0.8[2] M⊕)
Radius (r) 0.15 RJ
(1.68 ± 0.09[1] R⊕)
Density (ρ) 5600 ± 1300[2] kg/m3
Temperature (T) 1300–1800[3] K
Discovery information
Discovery date February 3, 2009
Discoverer(s) Rouan et al. (COROT)
Detection method Transit
Discovery site Polar orbit
Discovery status Announced
Other designations
CoRoT-Exo-7b
Database references
Extrasolar Planets
Encyclopaedia		 data
SIMBAD data

COROT-7b (previously named COROT-Exo-7b)[4][5] is a reported exoplanet orbiting around the star COROT-7. It was first detected photometrically by the French-led COROT mission and reported in early 2009. It is the smallest exoplanet to have its diameter measured, at 1.7 times that of the Earth (which would give it a volume 4.9 times Earth's). The HARPS spectrograph was subsequently used to measure the mass of COROT-7b by the radial velocity method at about 4.8 Earth masses, giving it a density of 5.6 ± 1.3 g cm−3, similar to Earth's.[2] From this, it was concluded that the planet is not composed of pure iron. The likely composition is a predominantly rocky one, similar to Earth's, but with less iron and/or more water, due to the greater compression.[2] It orbits very close to its star (1/23rd the distance from the Sun to Mercury[6]) with an orbital period of exactly 20 hours, 29 minutes, and 9.7 seconds. The star, in the constellation Monoceros, is 150 parsecs (490 ly) away and is slightly smaller than the Sun.

Contents

Discovery

Artist conception of COROT-7b transiting yellow dwarf COROT-7.

COROT-7b was found by observing its parent star's periodic decrease in apparent magnitude caused by the planet's transit in front of the star as seen from Earth. Measuring this dip in brightness, together with a size estimate for the star, allows one to calculate the planet's size. (See Transit method.)

The discovery of COROT-7b was announced on 3 February 2009, during the COROT Symposium 2009 in Paris.[7] It will be published in a forthcoming special issue of the journal Astronomy and Astrophysics dedicated to results from COROT.[8]

Characteristics

Artist’s impression of COROT-7b.

The planet has a maximum surface temperature between 1800 to 2600 °C (3300 to 4700 degrees Fahrenheit).[2] Due to the high temperature, it may be covered in lava.[3] The composition and density of the planet are still being examined, with one possibility being that it is rocky like Earth. It may also belong to a class of planets that are thought to contain up to 40% water (in the form of ice and/or vapor) in addition to rock.[2] However, the fact that it formed so close to its parent star may mean that it is depleted of volatiles.[9] A strong possibility exists that the planet's rotation is tidally locked to the orbital period, so that temperatures and geologic conditions on the sides of the planet facing towards and away from the star may be dramatically different. Theoretical work also suggests that CoRoT-7b could be a Chthonian planet (the remains of a Neptune-like planet from which much of the initial mass has been removed due to close proximity to its parent star).[10][11]

With an orbital period of just 20 hours, the planet has the shortest orbit ever seen in any planet, extrasolar or otherwise.[12]

According to Suzanne Aigrain, a researcher at the University of Exeter who is part of the COROT team, the planet is much more earthlike than previously found exoplanets and probably has a solid surface somewhere.[12]

Any departure from circularity of its orbit (due to the influence of host star and neighboring planets) could generate intense volcanic activity similar to that of Io via tidal heating.[13]

Possible atmosphere

Due to the high temperatures on the illuminated side of the planet, and the likelihood that all surface volatiles have been depleted, silicate rock vaporization may have produced a tenuous atmosphere (with a pressure approaching 1 Pa or 10−2 bar at 2500 K) consisting predominantly of sodium, O2, O and silicon monoxide, as well as smaller amounts of potassium and other metals.[9][6] Magnesium (Mg), Aluminium (Al), Calcium (Ca), Silicon (Si), and Iron (Fe) may rain out from such an atmosphere on the planet's daylight side in the form of particles of minerals, such as enstatite, corundum and spinel, wollastonite, silica, and iron (II) oxide, that would condense at altitudes below 10 km. Titanium (Ti) may be depleted (and possibly iron similarly) by being transported towards the night side before condensing as perovskite and geikelite.[9] Sodium (and to a lesser extent, potassium), being more volatile, would be less subject to condensation into clouds, and would dominate the outer layers of the atmosphere.[9][6]

See also

  • COROT-7c: another close-orbiting super-Earth not detected by COROT
  • COROT is a CNES space mission to discover planets using the photometric transit method
  • Spitzer Space Telescope or SST
  • HARPS or High Accuracy Radial Velocity Planet Search
  • GJ 1214 b, another exoplanet with well determined radius and mass in the super-Earth range

References

  1. ^ a b c d e f g h i j A. Léger; et al. (2009). "Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius". Astronomy and Astrophysics (accepted). http://xxx.lanl.gov/abs/0908.0241. 
  2. ^ a b c d e f g Queloz, D.; et al. (2009). "The CoRoT-7 planetary system: two orbiting Super-Earths". Astronomy and Astrophysics 506: 303. doi:10.1051/0004-6361/200913096. http://www.aanda.org/articles/aa/pdf/forth/aa13096-09.pdf.  Also available from exoplanet.eu
  3. ^ a b "COROT discovers smallest exoplanet yet, with a surface to walk on". European Space Agency. 3 February 2009. http://www.esa.int/esaCP/SEM7G6XPXPF_index_0.html. Retrieved 2009-02-04. 
  4. ^ "Notes for planet CoRoT-7 b". Extrasolar Planets Encyclopedia. http://exoplanet.eu/planet.php?p1=CoRoT-7&p2=b. Retrieved 2009-03-17. 
  5. ^ Schneider, J. (10 March 2009). "Change in CoRoT planets names". Exoplanets mailing list. http://listes.obs.ujf-grenoble.fr/wws/arc/exoplanets/2009-03/msg00003.html. Retrieved 2009-03-19. 
  6. ^ a b c Lutz, Diana (2009-09-29). "Simulation suggests rocky exoplanet has bizarre atmosphere". Washington University in St. Louis News & Information. Washington University in St. Louis. http://news-info.wustl.edu/news/page/normal/14753.html. Retrieved 2009-10-02. 
  7. ^ Rouan et al. (3 February 2009). "CoRoT-exo-7b Has CoRoT discovered the first transiting Super-Earth around a main sequence star?". Corot Symposium – Paris. http://www.colloquium.eu/congres/09COROT/docs/slides/03mardi/11h/d_rouan/alancer.pdf. Retrieved 2009-05-13. 
  8. ^ University of Exeter (3 February 2009). "European team finds smallest transiting extrasolar planet ever". InSciences. http://insciences.org/article.php?article_id=1948. Retrieved 2009-02-04. 
  9. ^ a b c d Schaefer, L.; Fegley, B. (2009-10-01). "Chemistry of Silicate Atmospheres of Evaporating Super-Earths". The Astrophysical Journal (American Astronomical Society) 703: L113–L117. doi:10.1088/0004-637X/703/2/L113. http://www.iop.org/EJ/abstract/1538-4357/703/2/L113. Retrieved 2009-10-02. 
  10. ^ "Exoplanets Exposed to the Core". Astrobiology Magazine. 25 April 2009. http://www.astrobio.net/index.php?option=com_news&task=detail&id=3105. Retrieved 2009-07-13. 
  11. ^ "Super-Earth 'began as gas giant'". BBC News. 10 January 2010. http://news.bbc.co.uk/1/hi/sci/tech/8446125.stm. Retrieved 2010-01-10. 
  12. ^ a b "Tiniest exoplanet found". Nature. 3 February 2009. http://www.nature.com/news/2009/090203/full/news.2009.78.html. Retrieved 2009-02-07. 
  13. ^ Jaggard, Victoria (2010-02-05). ""Super Earth" May Really Be New Planet Type: Super-Io". National Geographic web site daily news. National Geographic Society. http://news.nationalgeographic.com/news/2010/02/100205-new-type-planet-corot-7b-io/. Retrieved 2010-02-12. 

External links

Coordinates: Sky map 06h 43m 49.0s, −01° 03′ 46.0″


COROT-7b
Extrasolar planet List of extrasolar planets
File:Exoplanet Comparison CoRoT-7
Size comparison of COROT-7b with Earth and Neptune.
Parent star

Star COROT-7
Constellation Monoceros
Right ascension (α) 06h 43m 49.0s[1]
Declination (δ) −01° 03′ 46.0″[1]
Apparent magnitude (mV) 11.668[1]
Distance489 ± 65[1] ly
(150 ± 20[1] pc)
Spectral type G9V[1]
Mass (m) 0.93 ± 0.03 M☉
Radius (r) 0.87 ± 0.04 R☉
Temperature (T) 5275 ± 75 K
Metallicity [Fe/H] 0.03 ± 0.06
Age 1.2 – 2.3 Gyr
Orbital elements

Semimajor axis(a) 0.0172 ± 0.00029[1] AU
(2.58 Gm)
    0.115 mas
Eccentricity (e) 0
Orbital period(P) 0.853585 ± 0.000024[1] d
    (20.48604 h)
Inclination (i) 80.1 ± 0.3[1]°
Semi-amplitude (K) 3.3[2] m/s
Physical characteristics

Mass(m)0.0151 ± 0.0025 MJ
(4.8 ± 0.8[2] M⊕)
Radius(r)0.15 RJ
(1.68 ± 0.09[1] R⊕)
Density(ρ)5600 ± 1300[2] kg/m3
Surface gravity(g)1.7 -0.4/+0.5 g
Temperature (T) 1300–1800[3] K
Discovery information

Discovery date February 3, 2009
Discoverer(s) Rouan et al. (COROT)
Detection method Transit
Discovery site Polar orbit
Discovery status Announced
Other designations
CoRoT-Exo-7b

Database references
Extrasolar Planets
Encyclopaedia		data
SIMBADdata

COROT-7b (previously named COROT-Exo-7b)[3][4] is a reported exoplanet orbiting around the star COROT-7. It was first detected photometrically by the French-led COROT mission and reported in early 2009.[5] It is the smallest exoplanet to have its diameter measured, at 1.7 times that of the Earth (which would give it a volume 4.9 times Earth's), and the first potential extrasolar terrestrial planet. The HARPS spectrograph was subsequently used to measure the mass of COROT-7b by the radial velocity method at about 4.8 Earth masses, giving it a density of 5.6 ± 1.3 g cm−3, similar to Earth's.[2] From this, it was concluded that the planet is not composed of pure iron. The likely composition is a predominantly rocky one, similar to Earth's, but with less iron and/or more water, due to the greater compression.[2] It orbits very close to its star (1/23rd the distance from the Sun to Mercury[6]) with an orbital period of 20 hours, 29 minutes, and 9.7 seconds. The star, in the constellation Monoceros, is 150 parsecs (490 ly) away and is slightly smaller than the Sun.

Contents

Discovery 

yellow dwarf COROT-7.]]

COROT-7b was found by observing its parent star's periodic decrease in apparent magnitude caused by the planet's transit in front of the star as seen from Earth. Measuring this dip in brightness, together with a size estimate for the star, allows one to calculate the planet's size. (See Transit method.)

The discovery of COROT-7b was announced on 3 February 2009, during the COROT Symposium 2009 in Paris.[5] It was published in a special issue of the journal Astronomy and Astrophysics dedicated to results from COROT.[7]

Characteristics

File:Artist’s impression of Corot-7b .jpg
Artist’s impression of COROT-7b.

The planet has a maximum surface temperature between 1800 to 2600 °C (3300 to 4700 degrees Fahrenheit).[2] Due to the high temperature, it may be covered in lava.[3] The composition and density of the planet are still being examined, with one possibility being that it is rocky like Earth. It may also belong to a class of planets that are thought to contain up to 40% water (in the form of ice and/or vapor) in addition to rock.[2] However, the fact that it formed so close to its parent star may mean that it is depleted of volatiles.[8] A strong possibility exists that the planet's rotation is tidally locked to the orbital period, so that temperatures and geologic conditions on the sides of the planet facing towards and away from the star may be dramatically different. Theoretical work also suggests that CoRoT-7b could be a Chthonian planet (the remains of a Neptune-like planet from which much of the initial mass has been removed due to close proximity to its parent star).[9][10]

With an orbital period of just 20 hours, the planet has the shortest orbit ever seen in any planet, extrasolar or otherwise.[11]

According to Suzanne Aigrain, a researcher at the University of Exeter who is part of the COROT team, the planet is much more earthlike than previously found exoplanets and probably has a solid surface somewhere.[11]

Any departure from circularity of its orbit (due to the influence of host star and neighboring planets) could generate intense volcanic activity similar to that of Io, via tidal heating.[12]

Model of the interior[13]

This planet was modeled to have convection in the mantle with a small core with no more than 15% the mass of the planet, or 0.7 M⊕. The lower mantle above the core-mantle boundary has more sluggish convection than the upper mantle because the greater pressure causes fluids to become more viscous. The temperature of the upper convecting mantle is different from one side of the planet to the other with lateral temperature differences for downwellings up to several hundred kelvins. However, the temperature of the upwelling is unaffected by downwelling and surface temperature variations. On the permanent dayside of the tidally-locked planet where the surface temperature is hot from continuously facing its sun, the surface takes part in convection, which is the evidence that all the surface of this hemisphere being covered in oceans of lava. On the permanent nightside, the surface is cool enough for the formation of the crust with pools of lava above the convective mantle with intense volcanism. The dayside of the planet has larger convection cells than the nightside.

Possible atmosphere

Due to the high temperatures on the illuminated side of the planet, and the likelihood that all surface volatiles have been depleted, silicate rock vaporization may have produced a tenuous atmosphere (with a pressure approaching 1 Pa or 10−2 bar at 2500 K) consisting predominantly of sodium, O2, O and silicon monoxide, as well as smaller amounts of potassium and other metals.[6][8] Magnesium (Mg), Aluminium (Al), Calcium (Ca), Silicon (Si), and Iron (Fe) may rain out from such an atmosphere on the planet's daylight side in the form of particles of minerals, such as enstatite, corundum and spinel, wollastonite, silica, and iron (II) oxide, that would condense at altitudes below 10 km. Titanium (Ti) may be depleted (and possibly iron similarly) by being transported towards the night side before condensing as perovskite and geikelite.[8] Sodium (and to a lesser extent, potassium), being more volatile, would be less subject to condensation into clouds, and would dominate the outer layers of the atmosphere.[6][8]

See also

  • COROT-7c: another close-orbiting super-Earth not detected by COROT
  • COROT is a CNES space mission to discover planets using the photometric transit method
  • Spitzer Space Telescope or SST
  • HARPS or High Accuracy Radial Velocity Planet Search
  • GJ 1214 b, another exoplanet with well determined radius and mass in the super-Earth range

References

  1. ^ a b c d e f g h i j A. Léger; et al. (2009). "Transiting exoplanets from the CoRoT space mission VIII. CoRoT-7b: the first Super-Earth with measured radius". Astronomy and Astrophysics 506: 287–302. doi:10.1051/0004-6361/200911933. http://www.aanda.org/articles/aa/pdf/2009/40/aa11933-09.pdf. 
  2. ^ a b c d e f g Queloz, D.; et al. (2009). "The CoRoT-7 planetary system: two orbiting Super-Earths". Astronomy and Astrophysics 506: 303. doi:10.1051/0004-6361/200913096. http://www.aanda.org/articles/aa/pdf/forth/aa13096-09.pdf.  Also available from exoplanet.eu
  3. ^ a b c "COROT discovers smallest exoplanet yet, with a surface to walk on". European Space Agency. 3 February 2009. http://www.esa.int/esaCP/SEM7G6XPXPF_index_0.html. Retrieved 2009-02-04. 
  4. ^ Schneider, J. (10 March 2009). "Change in CoRoT planets names". Exoplanets mailing list. http://listes.obs.ujf-grenoble.fr/wws/arc/exoplanets/2009-03/msg00003.html. Retrieved 2009-03-19. 
  5. ^ a b Rouan et al. (3 February 2009). "CoRoT-exo-7b Has CoRoT discovered the first transiting Super-Earth around a main sequence star?". Corot Symposium – Paris. http://www.colloquium.eu/congres/09COROT/docs/slides/03mardi/11h/d_rouan/alancer.pdf. Retrieved 2009-05-13. 
  6. ^ a b c Lutz, Diana (2009-09-29). "Simulation suggests rocky exoplanet has bizarre atmosphere". Washington University in St. Louis News & Information. Washington University in St. Louis. http://news-info.wustl.edu/news/page/normal/14753.html. Retrieved 2009-10-02. 
  7. ^ ""The CoRoT space mission: early results", Astronomy and Astrophysics, Vol. 506 No. 1 (October IV 2009)". http://www.aanda.org/index.php?option=com_toc&url=/articles/aa/abs/2009/40/contents/contents.html. Retrieved 2010-08-23. 
  8. ^ a b c d Schaefer, L.; Fegley, B. (2009-10-01). "Chemistry of Silicate Atmospheres of Evaporating Super-Earths". The Astrophysical Journal (American Astronomical Society) 703: L113–L117. doi:10.1088/0004-637X/703/2/L113. http://www.iop.org/EJ/abstract/1538-4357/703/2/L113. Retrieved 2009-10-02. 
  9. ^ "Exoplanets Exposed to the Core". Astrobiology Magazine. 25 April 2009. http://www.astrobio.net/index.php?option=com_news&task=detail&id=3105. Retrieved 2009-07-13. 
  10. ^ "Super-Earth 'began as gas giant'". BBC News. 10 January 2010. http://news.bbc.co.uk/1/hi/sci/tech/8446125.stm. Retrieved 2010-01-10. 
  11. ^ a b "Tiniest exoplanet found". Nature. 3 February 2009. http://www.nature.com/news/2009/090203/full/news.2009.78.html. Retrieved 2009-02-07. 
  12. ^ Jaggard, Victoria (2010-02-05). ""Super Earth" May Really Be New Planet Type: Super-Io". National Geographic web site daily news. National Geographic Society. http://news.nationalgeographic.com/news/2010/02/100205-new-type-planet-corot-7b-io/. Retrieved 2010-02-12. 
  13. ^ Noack, Lena; Stamenkovic, Vlada; Wagner, Frank W.; Sohl, Frank; Breuer, Doris (2010). "CoRoT-7b: Convection in a Tidally Locked Planet". EGU 12. http://meetingorganizer.copernicus.org/EGU2010/EGU2010-9759.pdf. Retrieved 2010-04-04. 

External links

Coordinates: 06h 43m 49.0s, −01° 03′ 46.0″

Retrieved from "http://yak.rapint.com/wiki/COROT-7b"







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