Kepler-62f

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Kepler-62f
The diagram compares the planets of the inner solar system to Kepler-62.jpg
Artist's impression of the Kepler-62 system (sizes to scale) compared to the planets of the inner Solar System with their respective habitable zones.
Discovery
Discovered by Kepler space telescope
Discovery date18 April 2013 [1] [2]
Transit [1]
Orbital characteristics
0.718 ± 0.007 [1] AU
Eccentricity ~0 [1]
267.291 ± 0.005 [1] d
Inclination 89.90 ± 0.03 [1]
Star Kepler-62 (KOI-701)
Physical characteristics
1.461±0.070  R🜨 [3]
Mass 2.8±0.4  M🜨 [1]
Temperature Teq: 208 K (−65 °C; −85 °F)

    Kepler-62f [1] [2] [4] (also known by its Kepler Object of Interest designation KOI-701.04) is a super-Earth exoplanet orbiting within the habitable zone of the star Kepler-62, the outermost of five such planets discovered around the star by NASA's Kepler space telescope. It is located about 980 light-years (300 parsecs ) from Earth in the constellation of Lyra. [5]

    Contents

    Kepler-62f orbits its parent star at a distance of 0.718 AU (107,400,000 km; 66,700,000 mi) from its host star with an orbital period of roughly 267 days, and has a radius of around 1.41 times that of Earth. It is one of the more promising candidates for potential habitability, as its parent star is a relatively quiet star, and has less mass than the Sun – thus it can live up to a span of about 30 billion years or so. [6] Based on its size, Kepler-62f is likely a terrestrial or ocean-covered planet. However, key components of the exoplanet still need to be assessed to determine habitability; such as its atmosphere if one exists, since it lies within the outer part of its host star's habitable zone. [1] [7]

    The discovery of the exoplanet–along with Kepler-62e–was announced in April 2013 by NASA as part of the Kepler space telescope data release. [1] The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. According to scientists, it is a potential candidate to search for extraterrestrial life, and was chosen as one of the targets to study by the Search for Extraterrestrial Intelligence (SETI) program. [8]

    Physical characteristics

    Mass, radius and temperature

    Kepler-62f is a super-Earth, placing it within the class of exoplanets with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. It has an equilibrium temperature of 208 K (−65 °C; −85 °F), close to that of Mars’s temperature. [9] It has a radius of 1.46 R🜨, [1] placing it below the radius of ≥1.6 R🜨 where it would otherwise be a mini-Neptune with a volatile composition, with no solid surface. [10] Due to its radius, it is likely a rocky planet. However, the mass isn't constrained yet, estimates place an upper limit of <35 ME, the real mass is expected to be significantly lower than this. [1] The Planetary Habitability Laboratory estimated a mass of around 2.6 ME, assuming a rocky Earth-like composition. [11]

    Host star

    The planet orbits a (K-type) star named Kepler-62, orbited by a total of five known planets. [1] The star has a mass of 0.69 M☉ and a radius of 0.64 R☉. It has a temperature of 4925 K and is 7 billion years old. [1] In comparison, the Sun is 4.6 billion years old [12] and has a temperature of 5778 K. [13] The star is somewhat metal-poor, with a metallicity ([Fe/H]) of −0.37, or 42% of the solar amount. [1] Its luminosity (L☉) is 21% that of the Sun. [1]

    The star's apparent magnitude, or how bright it appears from Earth's perspective, is 13.65. Therefore, it is too dim to be seen with the naked eye.

    Orbit

    Kepler-62f orbits its host star every 267.29 days at a semi-major axis distance of about 0.718 astronomical units (107,400,000 km, 66,700,000 mi), which is roughly the same as Venus's semi-major axis from the Sun. Compared to Earth, this is about seven-tenths of the distance from it to the Sun. Kepler-62f is estimated to receive about 41% of the amount of sunlight that Earth does from the Sun, which is comparable to Mars, which receives 43%. [1]

    Habitability

    Artist's conception of Kepler-62f (foreground) as a rocky terrestrial exoplanet orbiting its host star (center). The actual appearance is not known. Kepler-62e can be seen in the distance as a twinkling star. Kepler-62f with 62e as Morning Star.jpg
    Artist's conception of Kepler-62f (foreground) as a rocky terrestrial exoplanet orbiting its host star (center). The actual appearance is not known. Kepler-62e can be seen in the distance as a twinkling star.

    Given the planet's age (7 ± 4 billion years), irradiance (0.41 ± 0.05 times Earth's) and radius (1.46 ± 0.07 times Earth's), a rocky (silicate-iron) composition with the addition of a possibly substantial amount of water is considered plausible. [1] A modeling study indicates it is likely that a great majority of planets in its size range are completely covered by ocean. [14] [15] If its density is the same as Earth's, its mass would be 1.413 or 2.80 times Earth's. The planet has the potential for hosting a moon according to a study of tidal effects on potentially habitable planets. [16] The planet may be the only habitable-zone candidate which would avoid desiccation by irradiation from the host star at its current location. [17]

    Climate

    Although Kepler-62f may be an ocean-covered planet possessing rock and water at the surface, it is the farthest out from its star, so without a supplementary amount of carbon dioxide (CO
    2    ), it may be a planet covered entirely in ice. [18] In order for Kepler-62f to sustain an Earth-like climate (with an average temperature of around 284–290 K (11–17 °C; 52–62 °F), at least 5 bars (4.9 atm) of carbon dioxide would have to be present in the planet's atmosphere. [19]

    On 13 May 2016, researchers at University of California, Los Angeles (UCLA) announced that they had found various scenarios that allow the exoplanet to be habitable. They tested several simulations based on Kepler-62f having an atmosphere that ranges in thickness from the same as Earth's all the way up to 12 times thicker than our planet's, various concentrations of carbon dioxide in its atmosphere, ranging from the same amount as is in the Earth's atmosphere up to 2,500 times that level and several different possible configurations for its orbital path. [19] In June 2018, studies suggest that Kepler-62f may have seasons and a climate similar to those on Earth. [20] [21]

    Other factors

    Because it is the outermost planet of its star system, the effects of tidal evolution from the inner planets and the host star on Kepler-62f are not likely to have had significant outcomes over its lifetime. The axial tilt is likely to have been unchanged, and thus, the planet may have an axial tilt (anywhere from 14°–30°) and rotational period somewhat similar to Earth. [22] This can further make the planet more sustainable for habitability, as it would be able to transfer heat to the night side, instead of it being a planet with its surface being half water and half ice.

    K-type stars like Kepler-62 can live for approximately 20–40 billion years, 2 to 4 times longer than the estimated lifetime of the Sun. [6] The low stellar activity of orange dwarfs like Kepler-62, creates a relatively benign radiation environment for planets orbiting in their habitable zones, increasing their potential habitability. [23] One review essay in 2015 concluded that Kepler-62f, along with the exoplanets Kepler-186f and Kepler-442b, were likely the best candidates for being potentially habitable planets. [24] [25]

    Discovery

    Confirmed small exoplanets in habitable zones (artist's impressions). (Kepler-62e, 62f, 186f, 296e, 296f, 438b, 440b, 442b) KeplerExoplanets-NearEarthSize-HabitableZone-20150106.png
    Confirmed small exoplanets in habitable zones (artist's impressions).
    (Kepler-62e, 62f, 186f, 296e, 296f, 438b, 440b, 442b)

    NASA's Kepler spacecraft observed 150000 stars in the Kepler Input Catalog, including Kepler-62, between 13 May 2009 and 17 March 2012. The software pipeline that searched for periodic dip in the stellar brightness, the sign of a planetary transit of the star, initially found three planets around Kepler-62, including Kepler-62e. Due to a bug in the software pipeline, the planet 62f was missed. Eric Agol, a Professor of Astronomy at the University of Washington, discovered three additional transits that had been missed by the pipeline, [2] which occurred every 267 days, and with a more detailed analysis the Kepler team concluded that a fourth planetary body, 62f, was responsible for the periodic 267-day transits. The discovery, along with the planetary system of the star Kepler-69 were announced on April 18, 2013. [1]

    Follow-up studies

    On 9 May 2013, a congressional hearing (Archived 2014-12-06 at the Wayback Machine ) by two U.S. House of Representatives subcommittees discussed "Exoplanet Discoveries: Have We Found Other Earths?," prompted by the discovery of exoplanet Kepler-62f, along with Kepler-62e and Kepler-69c. A related special issue of the journal Science, published earlier, described the discovery of the exoplanets. [27]

    At about 980 light-years (300 parsecs) distant, Kepler-62f is too remote and its star too far for current telescopes or the next generation of planned telescopes to determine its mass or whether it has an atmosphere. The Kepler spacecraft focused on a single small region of the sky but next-generation planet-hunting space telescopes, such as TESS and CHEOPS, will examine nearby stars throughout the sky.

    Nearby stars with planets can then be studied by the upcoming James Webb Space Telescope and future large ground-based telescopes to analyze atmospheres, determine masses and infer compositions. Additionally the Square Kilometer Array would significantly improve radio observations over the Arecibo Observatory and Green Bank Telescope. [28]

    Extraterrestrial intelligence target

    Kepler-62f and the other Kepler-62 exoplanets are being specially targeted as part of the Search for Extraterrestrial Intelligence (SETI) search programs. [8] They will scan the areas for any signals that may represent technological life in the system. Given the interstellar distance of 980 light-years (300 parsecs), the signals would have left the planet that many years ago.[ clarification needed ] As of 2016, no such signals have been found.

    See also

    Related Research Articles

    <span class="mw-page-title-main">Exoplanet</span> Planet outside the Solar System

    An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not then recognized as such. The first confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. According to statistics from the NASA Exoplanet Archive, As of 21 August 2024, there are 5,747 confirmed exoplanets in 4,289 planetary systems, with 962 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.

    <span class="mw-page-title-main">Habitable zone</span> Orbits where planets may have liquid surface water

    In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the HZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the HZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence.

    <span class="mw-page-title-main">Ocean world</span> Planet containing a significant amount of water or other liquid

    An ocean world, ocean planet or water world is a type of planet that contains a substantial amount of water in the form of oceans, as part of its hydrosphere, either beneath the surface, as subsurface oceans, or on the surface, potentially submerging all dry land. The term ocean world is also used sometimes for astronomical bodies with an ocean composed of a different fluid or thalassogen, such as lava, ammonia or hydrocarbons. The study of extraterrestrial oceans is referred to as planetary oceanography.

    <span class="mw-page-title-main">Super-Earth</span> Type of exoplanet

    A Super-Earth is a type of exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term.

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

    An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. 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 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.

    <span class="mw-page-title-main">Kepler-22b</span> Super-Earth exoplanet orbiting Kepler-22

    Kepler-22b is an exoplanet orbiting within the habitable zone of the Sun-like star Kepler-22. It is located about 640 light-years from Earth in the constellation of Cygnus. It was discovered by NASA's Kepler Space Telescope in December 2011 and was the first known transiting planet to orbit within the habitable zone of a Sun-like star, where liquid water could exist on the planet's surface. Kepler-22 is too dim to be seen with the naked eye.

    <span class="mw-page-title-main">Kepler-69c</span> Super-Earth orbiting Kepler-69

    Kepler-69c is a confirmed super-Earth extrasolar planet, likely rocky, orbiting the Sun-like star Kepler-69, the outermore of two such planets discovered by NASA's Kepler spacecraft. It is located about 2,430 light-years from Earth.

    <span class="mw-page-title-main">Kepler-62</span> K-type star in the constellation Lyra

    Kepler-62 is a K-type main sequence star cooler and smaller than the Sun, located roughly 980 light-years from Earth in the constellation Lyra. It resides within the field of vision of the Kepler spacecraft, the satellite that NASA's Kepler Mission used to detect planets that may be transiting their stars. On April 18, 2013, it was announced that the star has five planets, two of which, Kepler-62e and Kepler-62f are within the star's habitable zone. The outermost, Kepler-62f, is likely a rocky planet.

    <span class="mw-page-title-main">Kepler-62e</span> Habitable-zone super-Earth planet orbiting Kepler-62

    Kepler-62e is a super-Earth exoplanet discovered orbiting within the habitable zone of Kepler-62, the second outermost of five such planets discovered by NASA's Kepler spacecraft. Kepler-62e is located about 990 light-years from Earth in the constellation of Lyra. The exoplanet was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-62e may be a terrestrial or ocean-covered planet; it lies in the inner part of its host star's habitable zone.

    <span class="mw-page-title-main">Kepler-186f</span> Terrestrial exoplanet orbiting Kepler-186

    Kepler-186f is an Earth-sized exoplanet orbiting within the habitable zone of the red dwarf star Kepler-186, the outermost of five such planets discovered around the star by NASA's Kepler space telescope. It is located about 580 light-years from Earth in the constellation of Cygnus.

    <span class="mw-page-title-main">Kepler-438b</span> Super-Earth orbiting Kepler-438

    Kepler-438b is a confirmed near-Earth-sized exoplanet. It is likely rocky. It orbits on the inner edge of the habitable zone of a red dwarf, Kepler-438, about 472.9 light-years from Earth in the constellation Lyra. It receives 1.4 times our solar flux. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015.

    <span class="mw-page-title-main">Kepler-442b</span> Super-Earth orbiting Kepler-442

    Kepler-442b is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the K-type main-sequence star Kepler-442, about 1,206 light-years (370 pc) from Earth in the constellation of Lyra.

    <span class="mw-page-title-main">Kepler-452b</span> Super-Earth exoplanet orbiting Kepler452

    Kepler-452b is a super-Earth exoplanet orbiting within the inner edge of the habitable zone of the sun-like star Kepler-452 and is the only planet in the system discovered by the Kepler space telescope. It is located about 1,400 light-years (430 pc) from Earth in the constellation of Cygnus.

    <span class="mw-page-title-main">Kepler-1229b</span> Super-Earth orbiting Kepler-1229

    Kepler-1229b is a confirmed super-Earth exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf Kepler-1229, located about 870 light years from Earth in the constellation of Cygnus. It was discovered in 2016 by the Kepler space telescope. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured.

    Kepler-1229 is a red dwarf star located about 875 light-years (268 pc) away from the Earth in the constellation of Cygnus. It is known to host a super-Earth exoplanet within its habitable zone, Kepler-1229b, which was discovered in 2016.

    TOI-700 is a red dwarf 101.4 light-years away from Earth located in the Dorado constellation that hosts TOI-700 d, the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS).

    <span class="mw-page-title-main">Kepler-1649c</span> Earth-size exoplanet orbiting Kepler-1649

    Kepler-1649c is an Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the red dwarf star Kepler-1649, the outermost planet of the planetary system discovered by Kepler’s space telescope. It is located about 301 light-years (92 pc) away from Earth, in the constellation of Cygnus.

    <span class="mw-page-title-main">Habitability of yellow dwarf systems</span> Likelihood of finding extraterrestrial life in yellow dwarf systems

    Habitability of G V stars of G V stars systems defines the suitability for life of exoplanets belonging to yellow dwarf stars. These systems are the object of study among the scientific community because they are considered the most suitable for harboring living organisms, together with those belonging to K-type stars.

    References

    1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Borucki, William J.; et al. (18 April 2013). "Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone". Science Express. 340 (6132): 587–590. arXiv: 1304.7387 . Bibcode:2013Sci...340..587B. doi:10.1126/science.1234702. PMID   23599262. S2CID   21029755.
    2. 1 2 3 Johnson, Michele; Harrington, J.D. (18 April 2013). "NASA's Kepler Discovers Its Smallest 'Habitable Zone' Planets to Date". NASA . Retrieved 18 April 2013.
    3. ↑ Borucki, William; Thompson, Susan E.; Agol, Eric; Hedges, Christina (May 2019). "Kepler-62f: Kepler's First Small Planet in the Habitable Zone, but Is It Real?". New Astronomy Reviews. 83: 28–36. arXiv: 1905.05719 . Bibcode:2018NewAR..83...28B. doi:10.1016/j.newar.2019.03.002. S2CID   153313459.
    4. ↑ Overbye, Dennis (18 April 2013). "2 Good Places to Live, 1,200 Light-Years Away". New York Times . Retrieved 18 April 2013.
    5. ↑ "Kepler-62f: A Possible Water World". Space.com . 13 May 2016.
    6. 1 2 Paul Glister (August 12, 2009). "In Praise of K-class Stars". Centauri Dreams. Retrieved July 2, 2016.
    7. ↑ "3 Potentially Habitable Super-Earth Planets Explained (Infographic)". Space.com . 18 April 2013.
    8. 1 2 "Has Kepler Found Ideal SETI-target Planets?". SETI Institute . 19 April 2013. Archived from the original on 29 October 2013. Retrieved 17 September 2013.
    9. ↑ "Kepler-62 f". NASA Exoplanet Archive. Retrieved 23 July 2016.
    10. ↑ Rogers, Leslie A. (31 July 2014). "Most 1.6 Earth-radius planets are not rocky". The Astrophysical Journal. 801 (1): 41. arXiv: 1407.4457 . Bibcode:2015ApJ...801...41R. doi:10.1088/0004-637X/801/1/41. S2CID   9472389.
    11. ↑ Mendez, Abel (April 18, 2013). "NASA Kepler Discovers New Potentially Habitable Exoplanets". Planetary Habitability Laboratory. Archived from the original on 2019-10-21. Retrieved August 10, 2016.
    12. ↑ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
    13. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
    14. ↑ "Water worlds surface: Planets covered by global ocean with no land in sight". Harvard Gazette. 18 April 2013. Retrieved 19 April 2013.
    15. ↑ Kaltenegger, L.; Sasselov, D.; Rugheimer, S. (18 April 2013). "Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the case of Kepler-62e and -62f". The Astrophysical Journal . 775 (2): L47. arXiv: 1304.5058 . Bibcode:2013ApJ...775L..47K. doi:10.1088/2041-8205/775/2/L47. S2CID   256544.
    16. ↑ Sasaki, Takashi; Barnes, Jason W. (30 June 2014). "Longevity of moons around habitable planets". International Journal of Astrobiology . 13 (4): 324–336. Bibcode:2014IJAsB..13..324S. doi:10.1017/S1473550414000184. S2CID   120860148.
    17. ↑ Luger, Rodrigo; Barnes, Rory (2015). "Extreme Water Loss and Abiotic O2 Buildup On Planets Throughout the Habitable Zones of M Dwarfs". Astrobiology. 15 (2): 119–143. arXiv: 1411.7412 . Bibcode:2015AsBio..15..119L. doi:10.1089/ast.2014.1231. PMC   4323125 . PMID   25629240.
    18. ↑ "Water Planets in the Habitable Zone: A Closer Look at Kepler 62e and 62f". Harvard-Smithsonian Center for Astrophysics. Sci Tech Daily. April 22, 2013. Retrieved 2016-05-10.
    19. 1 2 Shields, Aomawa L.; et al. (2016). "The Effect of Orbital Configuration on the Possible Climates and Habitability of Kepler-62f". Astrobiology. 16 (6): 443–64. arXiv: 1603.01272 . Bibcode:2016AsBio..16..443S. doi:10.1089/ast.2015.1353. PMC   4900229 . PMID   27176715.
    20. ↑ Mack, Eric (29 June 2018). "Two Earth-like exoplanets (Kepler 186f and Kepler 62f) now even better spots to look for life - Two of the earliest Earth-ish exoplanet finds are now more exciting targets in the search for habitable worlds beyond this rock". CNET . Retrieved 29 June 2018.
    21. ↑ Shan, Yutong; Li, Gongjie (2018-05-16). "Obliquity Variations of Habitable Zone Planets Kepler-62f and Kepler-186f". The Astronomical Journal. 155 (6): 237. arXiv: 1710.07303 . Bibcode:2018AJ....155..237S. doi: 10.3847/1538-3881/aabfd1 . ISSN   1538-3881. S2CID   59033808.
    22. ↑ Adam Hanhazy (2015-02-19). "Planets Can Alter Each Other's Climates over Eons". Astrobiology. Archived from the original on 2015-09-30. Retrieved 2016-06-22.{{cite web}}: CS1 maint: unfit URL (link)
    23. ↑ "Life Could Easily Develop Around Orange Dwarfs". Softpedia. 7 May 2009. Retrieved May 17, 2016.
    24. ↑ Paul Gilster, Andrew LePage (2015-01-30). "A Review of the Best Habitable Planet Candidates". Centauri Dreams, Tau Zero Foundation. Retrieved 2015-07-24.
    25. ↑ NASA Astrobiology Strategy 2015 Archived 2016-12-22 at the Wayback Machine .(PDF), page 92, NASA
    26. ↑ Clavin, Whitney; Chou, Felicia; Johnson, Michele (6 January 2015). "NASA's Kepler Marks 1,000th Exoplanet Discovery, Uncovers More Small Worlds in Habitable Zones". NASA . Retrieved 6 January 2015.
    27. ↑ "Special Issue: Exoplanets". Science . 340 (6132). 3 May 2013. Retrieved 18 May 2013.
    28. ↑ Siemion, Andrew P.V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill (3 February 2013). "A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets". Astrophysical Journal. 767 (1): 94. arXiv: 1302.0845 . Bibcode:2013ApJ...767...94S. doi:10.1088/0004-637X/767/1/94. S2CID   119302350.
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