Discoveries of exoplanets

From Wikipedia, the free encyclopedia
  (Redirected from Discoveries of extrasolar planets)
Jump to: navigation, search
Number of extrasolar planet discoveries per year through 2014, with colors indicating method of detection:
  timing

An exoplanet (extrasolar planet) is a planet located outside the Solar System. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods such as the transit method and the radial-velocity method. As of September 12, 2014, astronomers have identified 1822 such planets (in 1137 planetary systems and 467 multiple planetary systems).[1] This is a list of the most notable discoveries.


1988–1992[edit]

  • Gamma Cephei Ab: The radial velocity variations of the star Gamma Cephei were announced in 1989, consistent with a planet in a 2.5-year orbit.[2] However misclassification of the star as a giant combined with an underestimation of the orbit of the Gamma Cephei binary, which implied the planet's orbit would be unstable, led some astronomers to suspect the variations were merely due to stellar rotation. The existence of the planet was finally confirmed in 2002.[3][4]
  • HD 114762 b: This object has a minimum mass 11 times the mass of Jupiter and has an 89-day orbit. At the time of its discovery it was regarded as a probable brown dwarf,[5] although subsequently it has been included in catalogues of extrasolar planets.[6][7]
  • PSR B1257+12: The first confirmed discovery of extrasolar planets was made in 1992 when a system of terrestrial-mass planets was announced to be present around the millisecond pulsar PSR B1257+12.[8]

1995–1998[edit]

  • 51 Pegasi b: In 1995 this became the first exoplanet orbiting a main-sequence star to have its existence confirmed. It is a hot Jupiter with a 4.2-day orbit.[9]
  • 47 Ursae Majoris b: In 1996 this Jupiter-like planet was the first long-period planet discovered, orbiting at 2.11 AU from the star with the eccentricity of 0.049. There is a second companion that orbits at 3.39 AU with the eccentricity of 0.220 ± 0.028 and a period of 2190 ± 460 days.
  • Gliese 876 b: In 1998, the first planet was found that orbits around a red dwarf star (Gliese 876). It is closer to its star than Mercury is to the Sun. More planets have subsequently been discovered even closer to the star.[10]

1999[edit]

  • Upsilon Andromedae: The first multiple-planetary system to be discovered around a main sequence star. It contains three planets, all of which are Jupiter-like. Planets b, c, d were announced in 1996, 1999, and 1999 respectively. Their masses are 0.687, 1.97, and 3.93 MJ; they orbit at 0.0595, 0.830, and 2.54 AU respectively.[11] In 2007 their inclinations were determined as non-coplanar.
  • HD 209458 b: After being originally discovered with the radial-velocity method, this became the first exoplanet to be seen transiting its parent star. The transit detection conclusively confirmed the existence of the planets suspected to be responsible for the radial velocity measurements.[12][13]

2001[edit]

  • HD 209458 b: Astronomers using the Hubble Space Telescope announced that they had detected the atmosphere of HD 209458 b. They found the spectroscopic signature of sodium in the atmosphere, but at a smaller intensity than expected, suggesting that high clouds obscure the lower atmospheric layers.[14] In 2008 the albedo of its cloud layer was measured, and its structure modeled as stratospheric.
  • Iota Draconis b: The first planet discovered around the giant star Iota Draconis, an orange giant. This provides evidence for the survival and behavior of planetary systems around giant stars. Giant stars have pulsations that can mimic the presence of planets. The planet is very massive and has a very eccentric orbit. It orbits on average 27.5% further from its star than Earth does from the Sun.[15] In 2008 the system's origin would be traced to the Hyades cluster, alongside Epsilon Tauri.

2003[edit]

  • PSR B1620-26 b: On July 10, using information obtained from the Hubble Space Telescope, a team of scientists led by Steinn Sigurðsson confirmed the oldest extrasolar planet yet. The planet is located in the globular star cluster M4, about 5,600 light years from Earth in the constellation Scorpius. This is one of only three planets known to orbit around a stellar binary; one of the stars in the binary is a pulsar and the other is a white dwarf. The planet has a mass twice that of Jupiter, and is estimated to be 12.7 billion years old.[16]

2004[edit]

Infrared image of 2M1207 (bluish) and 2M1207b (reddish). The two objects are separated by less than one arc second in Earth's sky. Image taken using the European Southern Observatory's 8.2 m Yepun Very Large Telescope
  • 2M1207 b: The first planet found around a brown dwarf. The planet is also the first to be directly imaged (in infrared). According to an early estimate, it has a mass 5 times that of Jupiter; other estimates give slightly lower masses. It was originally estimated to orbit at 55 AU from the brown dwarf. The brown dwarf is only 25 times as massive as Jupiter. The temperature of the gas giant planet is very high (1250 K), mostly due to gravitational contraction.[18] In late 2005, the parameters were revised to orbital radius 41 AU and mass of 3.3 Jupiters, because it was found that the system is closer to Earth than was originally believed. In 2006, a dust disk was found around 2M1207, providing evidence for active planet formation.[19]

2005[edit]

  • TrES-1 and HD 209458b: On March 22, two groups announced the first direct detection of light emitted by exoplanets, achieved with the Spitzer Space Telescope. These studies permitted the direct study of the temperature and structure of the planetary atmospheres.[20][21]
  • Gliese 876 d: On June 13, a third planet orbiting the red dwarf star Gliese 876 was announced. With a mass estimated at 7.5 times that of Earth, it may be rocky in composition. The planet orbits at 0.021 AU with a period of 1.94 days.[22]
  • HD 149026 b: This planet was announced on July 1. Its unusually high density indicated that it was a giant planet with a large core, the largest one yet known. The mass of the core was estimated at 70 Earth masses (as of 2008, 80-110), accounting for at least two-thirds of the planet's total mass.[23]

2006[edit]

  • OGLE-2005-BLG-390Lb: This planet, announced on January 25, was detected using the gravitational microlensing method. It orbits a red dwarf star around 21,500 light years from Earth, towards the center of the Milky Way galaxy. As of April 2010, it remains the most distant known exoplanet. Its mass is estimated to be 5.5 times that of Earth. Prior to this discovery, the few known exoplanets with comparably low masses had only been discovered in orbits very close to their parent stars, but this planet is estimated to have a relatively wide separation of 2.6 AU from its parent star. Due to that wide separation and due to the inherent dimness of the star, the planet is probably the coldest exoplanet known.[24][25]
  • HD 69830: Has a planetary system with three Neptune-mass planets. It is the first triple planetary system without any Jupiter-like planets discovered around a Sun-like star. All three planets were announced on May 18 by Lovis. All three orbit within 1 AU. The planets b, c and d have masses of 10, 12 and 18 times that of Earth, respectively. The outermost planet, d, appears to be in the habitable zone, shepherding a thick asteroid belt.[26]

2007[edit]

  • HD 209458 b and HD 189733 b: These became the first extrasolar planets to have their atmospheric spectra directly observed. The announcement was made on February 21, by two groups of researchers who had worked independently.[27] One group, led by Jeremy Richardson of NASA's Goddard Space Flight Center, observed the atmosphere of HD 209458 b over a wavelength range from 7.5 to 13.2 micrometres. The results were surprising in several ways. The 10-micrometre spectral peak of water vapor was absent. An unpredicted peak was observed at 9.65 micrometres, which the investigators attributed to clouds of silicate dust. Another peak, at 7.78 micrometres, remained unexplained.[28] The other group, led by Carl Grillmair of NASA's Spitzer Science Center, observed HD 189733 b. They also failed to detect the spectroscopic signature of water vapor.[29] Later in the year, yet another group of researchers using a somewhat different technique succeeded in detecting water vapor in the planet's atmosphere, the first time such a detection had been made.[30][31]
  • Gliese 581 c: A team of astronomers led by Stephane Udry used the HARPS instrument on the European Southern Observatory's 3.6-meter telescope to discover this exoplanet by means of the radial velocity method.[32] The team calculated that the planet could support liquid water and possibly life.[33] However, subsequent habitability studies indicate that the planet likely suffers from a runaway greenhouse effect similar to Venus, rendering the presence of liquid water impossible.[34][35] These studies suggest that the third planet in the system, Gliese 581 d, is more likely to be habitable. Seth Shostak, a senior astronomer with the SETI institute, stated that two unsuccessful searches had already been made for radio signals from extraterrestrial intelligence in the Gliese 581 system.[33]
  • Gliese 436 b: This planet was one of the first Neptune-mass planets discovered, in August 2004. In May 2007, a transit was found, revealed as the smallest and least massive transiting planet yet at 22 times that of Earth. Its density is consistent with a large core of an exotic form of solid water called "hot ice", which would exist, despite the planet's high temperatures, because the planet's gravity causes water to be extremely dense.[36]
  • TrES-4: The largest-diameter and lowest-density exoplanet to date, TrES-4 is 1.7 times Jupiter's diameter but only 0.84 times its mass, giving it a density of just 0.2 grams per cubic centimeter—about the same as balsa wood. It orbits its primary closely and is therefore quite hot, but stellar heating alone does not appear to explain its large size.[37]

2008[edit]

  • OGLE-2006-BLG-109Lb and OGLE-2006-BLG-109Lc: On February 14, the discovery of a planetary system was announced that is the most similar one known to the Jupiter-Saturn pair within the Solar System in terms of mass ratio and orbital parameters. The presence of planets with such parameters has implications for possible life in a solar system as Jupiter and Saturn have a stabilizing effect to the habitable zone by sweeping away large asteroids from the habitable zone.[38]
  • HD 189733 b: On March 20, follow-up studies to the first spectral analyses of an extrasolar planet were published in the scientific journal Nature, announcing evidence of an organic molecule found on an extrasolar planet for the first time. The analysis showed not only water vapor, but also methane existing in the atmosphere of the giant gas planet. Although conditions on there are too harsh to harbor life, it still is the first time a key molecule for organic life was found on an extrasolar planet.[39]
  • HD 40307: On June 16, Michel Mayor announced a planetary system with three super-Earths orbiting this K-type star. The planets have masses ranging from 4 to 9 Earth masses and periods ranging from 4 to 20 days. It was suggested this might be the first multi-planet system without any known gas giants. However, a subsequent study of the system's orbital stability found that tidal interactions have had little effect on evolution of the planets' orbits. That, in turn, suggests that the planets experience relatively low tidal dissipation and hence are of primarily gaseous composition.[40] All three were discovered by the HARPS spectrograph in La Silla, Chile.[41]
  • 1RXS J160929.1−210524: In September, an object was imaged in the infrared at a separation of 330AU from this star. Later, in June 2010, the object was confirmed to be a companion planet to the star rather than a background object aligned by chance.[42]
  • Fomalhaut b: On November 13, NASA and the Lawrence Livermore National Laboratory announced the discovery of an extrasolar planet orbiting just inside the debris ring of the A class star Fomalhaut (Alpha Piscis Austrini). This was the first extrasolar planet to be directly imaged by an optical telescope.[43] Its mass is estimated to be three times that of Jupiter.[44][45] Based on the planet's unexpected brightness at visible wavelengths, the discovery team suspects it is surrounded by its own large disk or ring that may be a satellite system in the process of formation.
  • HR 8799: Also on November 13, the discovery of three planets orbiting HR 8799 was announced. This was the first direct image of multiple planets. Christian Marois of the National Research Council of Canada's Herzberg Institute of Astrophysics and his team used the Keck and Gemini telescopes in Hawaii. The Gemini images allowed the international team to make the initial discovery of two of the planets with data obtained on October 17, 2007. Then, in July through September 2008 the team confirmed this discovery and found a third planet orbiting even closer to the star with images obtained at the Keck II telescope. A review of older data taken in 2004 with the Keck II telescope revealed that the outer 2 planets were visible on these images. Their masses and separations are approximately 7 MJ at 24 AU, 7 MJ at 38 AU, and 5 MJ at 68 AU.[45][46]

2009[edit]

  • COROT-7b: On February 3, the European Space Agency announced the discovery of a planet orbiting the star COROT-7. Although the planet orbits its star at a distance less than 0.02 AU, its diameter is estimated to be around 1.7 times that of Earth, making it the smallest super-Earth yet measured. Due to its extreme closeness to its parent star, it is believed to have a molten surface at a temperature of 1000–1500 °C.[47] It was discovered by the French COROT satellite.
  • Gliese 581 e: On April 21, the European Southern Observatory announced the discovery of a fourth planet orbiting the star Gliese 581. The planet orbits its parent star at a distance of less than 0.03 AU and has a minimum mass estimated at 1.9 times that of Earth. As of January 2010, this is the lightest known extrasolar planet to orbit a main-sequence star.[9]
  • 30 planets: On October 19, it was announced that 30 new planets were discovered, all were detected by radial velocity method. It is the most planets ever announced in a single day during the exoplanet era[clarification needed]. October 2009 now holds the most planets discovered in a month, breaking the record set in June 2002 and August 2009, during which 17 planets were discovered.
  • 61 Virginis and HD 1461: On December 14, three planets (one is super-Earth and two are Neptune-mass planets) were discovered. Also a super-Earth planet and two unconfirmed planets around HD 1461 were discovered. These discoveries indicated that low-mass planets that orbit around nearby stars are very common. 61 Virginis is the first star like the Sun to host the super-Earth planets.[48]
  • GJ 1214 b: On December 16, a super-Earth planet was discovered by transit. The determination of density from mass and radius suggest that this planet may be an ocean planet composed of 75% water and 25% rock. Some of the water on this planet should be in the exotic form of ice VII. This is the first planet discovered by MEarth Project, which is used to look for transits of super-Earth planets crossing the face of M-type stars.[49]

2010[edit]

  • 47 Ursae Majoris d: On March 6, a gas giant like Jupiter with the longest known orbital period for any exoplanet was detected via radial velocity. It orbits its parent star at a distance similar to Saturn in our solar system with its orbital period lasting about 38 Earth years.
  • COROT-9b: On March 17, the first known temperate transiting planet was announced. Discovered by the COROT satellite, it has an orbital period of 95 days and a periastron distance of 0.36 AU, by far the largest of any exoplanet whose transit has been observed. The temperature of the planet is estimated at between 250 K and 430 K (between -20°C and 160°C).[50]
  • Beta Pictoris b: On June 10, for the first time astronomers have been able to directly follow the motion of an exoplanet as it moves to the other side of its host star. The planet has the smallest orbit so far of all directly imaged exoplanets, lying as close to its host star as Saturn is to the Sun.[51]
  • HD 209458 b: On June 23, astronomers announced they have measured a superstorm for the first time in the atmosphere of HD 209458 b. The very high-precision observations done by ESO’s Very Large Telescope and its powerful CRIRES spectrograph of carbon monoxide gas show that it is streaming at enormous speed from the extremely hot day side to the cooler night side of the planet. The observations also allow another exciting “first” — measuring the orbital speed of the exoplanet itself, providing a direct determination of its mass.[52]
  • HD 10180: On August 24, astronomers using ESO’s HARPS instrument announced the discovery of a planetary system with up to seven planets orbiting a Sun-like star with five confirmed Neptune-mass planets and evidence of two other planets, one of which could have the lowest mass of any planet found to date orbiting a main-sequence star, and the other of which may be a long-period Saturnian planet. Additionally, there is evidence that the distances of the planets from their star follow a regular pattern, as seen in our Solar System.[53]

2011[edit]

  • Kepler 11: On February 3, astronomers using NASA's Kepler Mission announced the discovery of 6 transiting planets orbiting the star Kepler 11. Masses were confirmed using a new method called Transit Timing Variations. The architecture of the system is unique with 6 low mass, low density planets all packed in tight orbits around their host star. The 5 inner planets all orbit inside that of Mercury in our solar system. It is believed that these planets formed out past the snow line and migrated in to their current position.[54]
  • 55 Cancri e: On April 27, 2011, the super-earth 55 Cancri e was found to transit its host star using the MOST satellite. This planet has the shortest known orbital period of any extrasolar planet at .73 days. It is also the first time a super earth has been detected transiting a naked eye star (less than 6th magnitude in V band). The high density calculated suggests that the planet has a "rock-iron composition supplemented by a significant mass of water, gas, or other light elements".[55]

2012[edit]

Histogram of Exoplanet Discoveries - gold bar diplays new planets "verified by multiplicity" (February 26, 2014).
Histogram of Exoplanets by size - the gold bars represent Kepler's latest newly verified exoplanets (February 26, 2014).

2013[edit]

2014[edit]

On 26 February 2014, NASA announced the discovery of 715 newly verified exoplanets around 305 stars by the Kepler Space Telescope. The exoplanets were found using a statistical technique called "verification by multiplicity". 95% of the discovered exoplanets were smaller than Neptune and four, including Kepler-296f, were less than 2 1/2 the size of Earth and were in habitable zones where surface temperatures are suitable for liquid water.[64][65][66]

In July, 2014, NASA announced the determination of the most precise measurement so far attained for the size of an exoplanet (Kepler-93b);[67] the discovery of an exoplanet (Kepler-421b) that has the longest known year (704 days) of any transiting planet found so far;[68] and, finding very dry atmospheres on three exoplanets (HD 189733b, HD 209458b, WASP-12b) orbiting sun-like stars.[69]

References[edit]

  1. ^ Schneider, Jean (10 September 2011). "Interactive Extra-solar Planets Catalog". The Extrasolar Planets Encyclopedia. Retrieved 2011-09-10. 
  2. ^ Campbell, B.; Walker, G. A. H.; Yang, S. (1988). "A search for substellar companions to solar-type stars". The Astrophysical Journal 331: 902. doi:10.1086/166608.  edit
  3. ^ Cochran, W.D. et al. (2002). "A Planetary Companion to the Binary Star Gamma Cephei". Retrieved 2010-05-02. 
  4. ^ Walker, G.A.H. (2008). "The First High-Precision Radial Velocity Search for Extra-Solar Planets". arXiv:0812.3169v1 [astro-ph].
  5. ^ Latham, D. W. et al. (1989). "The unseen companion of HD114762 - A probable brown dwarf". Nature 339 (6219): 38–40. Bibcode:1989Natur.339...38L. doi:10.1038/339038a0. 
  6. ^ Schneider, J. "Notes for star HD 114762". The Extrasolar Planets Encyclopaedia. Retrieved 2010-05-02. 
  7. ^ "HD 114762 b". Exoplanets Data Explorer. Retrieved 2010-05-02. 
  8. ^ Wolszczan, A.; Frail, D. A. (1992). "A planetary system around the millisecond pulsar PSR1257 + 12". Nature 355 (6356): 145. doi:10.1038/355145a0.  edit
  9. ^ a b M. Mayor et al. (2009). "The HARPS search for southern extra-solar planets: XVIII. An Earth-mass planet in the GJ 581 planetary system". Astronomy and Astrophysics 507 (1): 487–494. arXiv:0906.2780. Bibcode:2009A&A...507..487M. doi:10.1051/0004-6361/200912172. 
  10. ^ J.N. Wilford (26 June 1998). "New Planet Detected Around a Star 15 Light Years Away". The New York Times. Retrieved 2008-07-17. 
  11. ^ B. Edgar, M. Watzke, C. Rasmussen. "Multiple planets discovered around Upsilon Andromedae". AFOE website. Retrieved 2009-12-06. 
  12. ^ D. Charbonneau et al. (2000). "Detection of Planetary Transits Across a Sun-like Star". Astrophysical Journal Letters 529 (1): L45–L48. arXiv:astro-ph/9911436. Bibcode:2000ApJ...529L..45C. doi:10.1086/312457. 
  13. ^ G.W. Henry et al. (2000). "A Transiting "51 Peg-like" Planet". Astrophysical Journal Letters 529 (1): L41–L44. Bibcode:2000ApJ...529L..41H. doi:10.1086/312458. 
  14. ^ D. Charbonneau et al. (2002). "Detection of an Extrasolar Planet Atmosphere". Astrophysical Journal 568 (1): 377–384. arXiv:astro-ph/0111544. Bibcode:2002ApJ...568..377C. doi:10.1086/338770. 
  15. ^ S. Frink et al. (2002). "Discovery of a Substellar Companion to the K2 III Giant Iota Draconis". Astrophysical Journal 576 (1): 478–484. Bibcode:2002ApJ...576..478F. doi:10.1086/341629. 
  16. ^ S. Sigurdsson et al. (2003). "A Young White Dwarf Companion to Pulsar B1620-26: Evidence for Early Planet Formation". Science 301 (5630): 193–196. arXiv:astro-ph/0307339. Bibcode:2003Sci...301..193S. doi:10.1126/science.1086326. PMID 12855802. 
  17. ^ "Fourteen Times the Earth – ESO HARPS Instrument Discovers Smallest Ever Extra-Solar Planet" (Press release). European Space Agency. 25 August 2004. Retrieved 2006-05-07. 
  18. ^ "Astronomers Confirm the First Image of a Planet Outside of Our Solar System" (Press release). European Space Agency. 30 April 2005. Retrieved 2009-12-06. 
  19. ^ S. Mohanty, R. Jayawardhana, N. Huelamo, E. Mamajek; Jayawardhana; Huélamo; Mamajek (2007). "The Planetary Mass Companion 2MASS 1207–3932B: Temperature, Mass, and Evidence for an Edge-on Disk". American Astronomical Society 657 (2): 1064–1091. arXiv:astro-ph/0610550. Bibcode:2007ApJ...657.1064M. doi:10.1086/510877. 
  20. ^ D. Charbonneau et al. (2005). "Detection of Thermal Emission from an Extrasolar Planet". Astrophysical Journal 626 (1): 523–529. arXiv:astro-ph/0503457. Bibcode:2005ApJ...626..523C. doi:10.1086/429991. 
  21. ^ D. Deming et al. (2005). "Infrared Radiation from an Extrasolar Planet". Nature 434 (7034): 740–743. arXiv:astro-ph/0503554. Bibcode:2005Natur.434..740D. doi:10.1038/nature03507. PMID 15785769. 
  22. ^ E.J. Rivera et al. (2005). "A 7.5 M Planet Orbiting the Nearby Star GJ 876". Astrophysical Journal 634 (1): 625–640. arXiv:astro-ph/0510508. Bibcode:2005ApJ...634..625R. doi:10.1086/491669. 
  23. ^ B. Sato et al. (2005). "The N2K Consortium II: A Transiting Hot Saturn around HD 149026 with a Large Dense Core". Astrophysical Journal 633 (1): 465–473. arXiv:astro-ph/0507009. Bibcode:2005ApJ...633..465S. doi:10.1086/449306. 
  24. ^ J.-P. Beaulieu, and others, Fouqué, P., Williams, A., Dominik, M., Jørgensen, U. G., Kubas, D., Cassan, A., Coutures, C., Greenhill, J., Hill, K., Menzies, J., Sackett, P. D., Albrow, M., Brillant, S., Caldwell, J. A. R., Calitz, J. J., Cook, K. H., Corrales, E., Desort, M., Dieters, S., Dominis, D., Donatowicz, J., Hoffman, M., Kane, S., Marquette, J.-B., Martin, R., Meintjes, P., Pollard, K. et al. (2006). "Discovery of a Cool Planet of 5.5 Earth Masses Through Gravitational Microlensing". Nature 439 (7075): 437–440. arXiv:astro-ph/0601563. Bibcode:2006Natur.439..437B. doi:10.1038/nature04441. PMID 16437108. 
  25. ^ "Kiwis help discover new planet". One News. 26 January 2006. Retrieved 2006-05-07. 
  26. ^ "Trio of Neptunes and their belt" (Press release). European Space Agency. 18 May 2006. Retrieved 2007-06-09. 
  27. ^ NASA's Spitzer First To Crack Open Light of Faraway Worlds Spitzer.caltech.edu 2007-02-21 Retrieved on 2008-07-17
  28. ^ L. Jeremy Richardson, Drake Deming, Karen Horning, Sara Seager, Joseph Harrington; Deming; Horning; Seager; Harrington (2007). "A spectrum of an extrasolar planet". Nature 445 (7130): 892–5. arXiv:astro-ph/0702507. Bibcode:2007Natur.445..892R. doi:10.1038/nature05636. PMID 17314975. 
  29. ^ C.J. Grillmair, D. Charbonneau, A. Burrows et al. (2007). "A Spitzer Spectrum of the Exoplanet HD 189733b". Astrophysical Journal Letters 658 (2): L115. arXiv:astro-ph/0702494. Bibcode:2007ApJ...658L.115G. doi:10.1086/513741. 
  30. ^ 'Clear Signs of Water' on Distant Planet at Space.com
  31. ^ Giovanna Tinetti, Alfred Vidal-Madjar, Mao-Chang Liang et al. (2007). "Water vapour in the atmosphere of a transiting extrasolar planet". Nature 448 (7150): 169–71. Bibcode:2007Natur.448..169T. doi:10.1038/nature06002. PMID 17625559. 
  32. ^ Udry et al. (2007). "The HARPS search for southern extra-solar planets, XI. Super-Earths (5 and 8 M) in a 3-planet system". Astronomy and Astrophysics 469 (3): L43–L47. arXiv:0704.3841. Bibcode:2007A&A...469L..43U. doi:10.1051/0004-6361:20077612. 
  33. ^ a b Ker Than (2007-04-24). "Major Discovery: New Planet Could Harbor Water and Life". Retrieved 2007-04-24. 
  34. ^ Selsis et al. (2007). "Habitable planets around the star Gl 581?". Astronomy and Astrophysics 476 (3): preprint. arXiv:0710.5294. Bibcode:2007A&A...476.1373S. doi:10.1051/0004-6361:20078091. 
  35. ^ von Bloh et al. (2007) "The Habitability of Super-Earths in Gliese 581". Astronomy & Astrophysics 476:1365-1371. Retrieved 2008-07-20. 
  36. ^ Fox, Maggie (2007-05-16). "Hot "ice" may cover recently discovered planet". Reuters. Retrieved 2009-04-23. 
  37. ^ "Largest Known Exoplanet Discovered". SPACE.com. 2007-08-06. Retrieved 2007-08-26. 
  38. ^ "Solar System Like Ours Found". SPACE.com. 2008-02-14. Retrieved 2008-02-19. 
  39. ^ "Key Organic Molecule Detected at Extrasolar Planet". SPACE.com. 2008-03-20. Retrieved 2008-03-20. 
  40. ^ Barnes et al. (2009-01-13). "The HD 40307 Planetary System: Super-Earths or Mini-Neptunes?". Astrophysical Journal 695 (2): 1006. arXiv:0901.1698. Bibcode:2009ApJ...695.1006B. doi:10.1088/0004-637X/695/2/1006. 
  41. ^ Mayor et al. (2008-06-16). "Trio of 'super-Earths' discovered". BBC news (London). Retrieved 2008-06-17. 
  42. ^ Astronomers verify directly imaged planet
  43. ^ "From afar, the first optical photos of an exoplanet". AFP. 2008-11-13. 
  44. ^ "Hubble Directly Observes a Planet Orbiting Another Star". Retrieved November 13, 2008. 
  45. ^ a b John Timmer. "Three planets directly observed orbiting distant star". Retrieved November 13, 2008. 
  46. ^ "Exoplanets finally come into view". London: BBC News. 2008-11-13. Retrieved 2009-04-23. 
  47. ^ "ESA Portal — COROT discovers smallest exoplanet yet, with a surface to walk on". Esa.int. 2009-02-03. Retrieved 2009-04-23. 
  48. ^ "New discoveries suggest low-mass planets are common around nearby stars". Astronomy.com. 2009-12-14. Retrieved 2009-12-21. 
  49. ^ "Astronomers find super-Earth using amateur, off-the-shelf technology". Astronomy.com. 2009-12-16. Retrieved 2009-12-21. 
  50. ^ Deeg, H. J.; Moutou, C.; Erikson, A.; Csizmadia, S; Tingley, B; Barge, P; Bruntt, H; Havel, M; Aigrain, S; Almenara, J. M.; Alonso, R.; Auvergne, M.; Baglin, A.; Barbieri, M.; Benz, W.; Bonomo, A. S.; Bordé, P.; Bouchy, F.; Cabrera, J.; Carone, L.; Carpano, S.; Ciardi, D.; Deleuil, M.; Dvorak, R.; Ferraz-Mello, S.; Fridlund, M.; Gandolfi, D.; Gazzano, J.-C.; Gillon, M. et al. (2010). "A transiting giant planet with a temperature between 250 K and 430 K". Nature 464 (7287): 384–387. Bibcode:2010Natur.464..384D. doi:10.1038/nature08856. PMID 20237564. 
  51. ^ "Exoplanet Caught on the Move". 2010-06-10. Retrieved 10 June 2010. 
  52. ^ Ignas A. G. Snellen et al. (2010). "The orbital motion, absolute mass and high-altitude winds of exoplanet HD 209458b". Nature 465 (7301): 1049–1051. arXiv:1006.4364. Bibcode:2010Natur.465.1049S. doi:10.1038/nature09111. PMID 20577209. 
  53. ^ "Richest Planetary System Discovered". 2010-08-24. Retrieved 24 August 2010. 
  54. ^ Lissauer, Jack J.; et al. (3 February 2011). "A closely packed system of low-mass, low-density planets transiting Kepler-11". Nature (journal). Retrieved 2012-01-07. 
  55. ^ Winn, Joshua N.; et al. (27 April 2011). "A Super-Earth Transiting a Naked-Eye Star". arXiv:1104.5230/.
  56. ^ a b Wang, Ji; et al. (January 3, 2013). "Planet Hunters. V. A Confirmed Jupiter-Size Planet in the Habitable Zone and 42 Planet Candidates from the Kepler Archive Data". arXiv. arXiv:1301.0644v1. Retrieved January 13, 2013. 
  57. ^ a b c Howell, Elizabeth (January 13, 2013). "Amateur Astronomers Discover 42 Alien Planets". Space.com. Retrieved January 13, 2013. 
  58. ^ Harrington, J. D.; Johnson, Michele (January 7, 2013). "NASA'S Kepler Mission Discovers 461 New Planet Candidates". NASA. Retrieved January 11, 2013. 
  59. ^ a b c Moskowitz, Clara (January 9, 2013). "Most Earth-Like Alien Planet Possibly Found". Space.com. Retrieved January 9, 2013. 
  60. ^ Staff. "NASA Exoplanet Archive-KOI-172.02". Caltech. Retrieved January 11, 2013. 
  61. ^ Johnson, Michele; Harrington, J.D. (18 April 2013). "NASA's Kepler Discovers Its Smallest 'Habitable Zone' Planets to Date". NASA. Retrieved 18 April 2013. 
  62. ^ Overbye, Dennis (18 April 2013). "2 Good Places to Live, 1,200 Light-Years Away". New York Times. Retrieved 4 February 2014. 
  63. ^ "NASA's Kepler Discovers Its Smallest 'Habitable Zone' Planets to Date". YouTube. 18 April 2013. Retrieved 19 April 2013. 
  64. ^ Johnson, Michele; Harrington, J.D. (26 February 2014). "NASA's Kepler Mission Announces a Planet Bonanza, 715 New Worlds". NASA. Retrieved 26 February 2014. 
  65. ^ Wall, Mike. "Population of Known Alien Planets Nearly Doubles as NASA Discovers 715 New Worlds". Retrieved 26 February 2014. 
  66. ^ "Kepler telescope bags huge haul of planets". Retrieved 27 February 2014. 
  67. ^ Claven, Whitney (23 July 2014). "The Most Precise Measurement of an Alien World's Size". NASA. Retrieved 25 July 2014. 
  68. ^ Johnson, Michele (21 July 2014). "Astronomers Discover Transiting Exoplanet with Longest Known Year". NASA. Retrieved 25 July 2014. 
  69. ^ Harrington, J.D.; Villard, Ray (24 July 2014). "RELEASE 14-197 - Hubble Finds Three Surprisingly Dry Exoplanets". NASA. Retrieved 25 July 2014. 

External links[edit]