HD 40307 d

Last updated
HD 40307 d
Discovery
Discovered by Mayor et al.
Discovery site La Silla Observatory, Chile
Discovery dateJune 16, 2008
radial velocity, using HARPS
Orbital characteristics
0.13210.12550.1387 AU
Eccentricity 0.0700.18 [1]
20.43220.40820.454 [1] d
Semi-amplitude 2.752.43.1 [1]
Star HD 40307

    HD 40307 d is an extrasolar planet orbiting the star HD 40307, located 42 light-years from Earth in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the HARPS apparatus in June 2008. It is the most massive of the six proposed planets in the system. [1] The planet is of interest as this star has relatively low metallicity, supporting a hypothesis that different metallicities in protostars determine what kind of planets they will form.

    Contents

    Discovery

    HD 40307 d was discovered through the Doppler spectroscopy method, which functions by measuring the variations in radial velocity in a star produced by the gravitational effect of orbiting exoplanets. [2] The radial velocities were measured by the High Accuracy Radial Velocity Planet Searcher spectrography system (HARPS) at the La Silla Observatory in Chile's Atacama Desert. The other less massive planets orbiting HD 40307 were discovered in the same way: HD 40307 b and HD 40307 c first, [2] and then HD 40307 e, HD 40307 f, and HD 40307 g. The discovery of HD 40307 d and the former two was announced at the astrophysics conference that took place on June 16–18, 2008 in Nantes, France. [2]

    Orbit and mass

    HD 40307 d has a mass of at least 9.2 times Earth's; assuming that all planets in the system have coplanar orbits, it is the most massive planet known in the system. [1] The planet orbits approximately 0.135 astronomical units from its primary star, as compared to Earth's orbit at approximately one astronomical unit away from the Sun. As a result, one year on HD 40307 d constitutes approximately 20.45 Earth days. The eccentricity of the planet's orbit was found to not differ significantly from zero, meaning that there is insufficient data to distinguish the orbit from an entirely circular one. [3]

    The star around which HD 40307 d orbits has an unusually low metallicity compared to that of other planet-bearing stars. This supports a hypothesis concerning the possibility that the metallicity of stars during their births may determine whether a protostar's accretion disk forms gas giants or terrestrial planets. [3]

    Characteristics

    The planet has not been found to transit and, further, it is not likely to. [1] It has also not been imaged. More specific physical characteristics such as radius, composition, and average surface temperature cannot be observed. [4]

    A dynamical study of planets b, c, and d showed tidal effects at least on b and c, to the extent that b had to be a sub-Neptune. All the planets from b to at least f must have migrated inward. That study implied that d was a sub-Neptune as well. [5]

    As such strong tidal forces often result in the destruction of larger natural satellites in planets orbiting close to a star, it is unlikely that HD 40307 d hosts any satellites. [6]

    See also

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    <span class="mw-page-title-main">HD 40307</span> Star in the constellation Pictor

    HD 40307 is an orange (K-type) main-sequence star located approximately 42 light-years away in the constellation of Pictor, taking its primary name from its Henry Draper Catalogue designation. It is calculated to be slightly less massive than the Sun. The star has six known planets, three discovered in 2008 and three more in 2012. One of them, HD 40307 g, is a potential super-Earth in the habitable zone, with an orbital period of about 200 days. This object might be capable of supporting liquid water on its surface, although much more information must be acquired before its habitability can be assessed.

    HD 40307 b is an extrasolar planet orbiting the star HD 40307, located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus, in June 2008. It is the second smallest of the planets orbiting the star, after HD 40307 e. The planet is of interest as this star has relatively low metallicity, supporting a hypothesis that different metallicities in protostars determine what kind of planets they will form.

    HD 40307 c is an extrasolar planet orbiting the star HD 40307, located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the HARPS apparatus, in June 2008. Of the six proposed planets in the HD 40307 star system, it is the third-largest, and has the second-closest orbit from the star. The planet is of interest as this star has relatively low metallicity, supporting a hypothesis that different metallicities in protostars determine what kind of planets they will form.

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    <span class="mw-page-title-main">HD 40307 g</span> Exoplanet candidate in the constellation of Pictor

    HD 40307 g is an exoplanet candidate suspected to be orbiting in the habitable zone of HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Göttingen, Germany.

    HD 40307 e is an extrasolar planet candidate suspected to be orbiting the star HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Göttingen, Germany.

    HD 40307 f is an extrasolar planet orbiting the star HD 40307. It is located 42 light-years away in the direction of the southern constellation Pictor. The planet was discovered by the radial velocity method, using the European Southern Observatory's HARPS apparatus by a team of astronomers led by Mikko Tuomi at the University of Hertfordshire and Guillem Anglada-Escude of the University of Göttingen, Germany. The existence of planet was confirmed in 2015.

    HD 109271 is a star in the constellation of Virgo. With an apparent magnitude of 8.05, it cannot be seen with the naked eye. Parallax measurements made by Gaia put the star at a distance of 182 light-years away.

    HD 3167 is a single, orange-hued star in the zodiac constellation of Pisces that hosts a system with three exoplanets. The star is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.97. The distance to HD 3167 can be determined from its annual parallax shift of 21.1363 mas as measured by the Gaia space observatory, yielding a range of 154 light years. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.204″ per year. Since it was first photographed during the Palomar observatory sky survey in 1953, it had moved over 12.5″ by 2017. The star is moving away from the Earth with an average heliocentric radial velocity of +19.5 km/s.

    References

    1. 1 2 3 4 5 6 Tuomi, Mikko; Anglada-Escudé, Guillem; Gerlach, Enrico; Jones, Hugh R. A.; Reiners, Ansgar; Rivera, Eugenio J.; Vogt, Steven S.; Butler, R. Paul (17 December 2012). "Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307". Astronomy & Astrophysics. 549: A48. arXiv: 1211.1617 . Bibcode:2013A&A...549A..48T. doi:10.1051/0004-6361/201220268. S2CID   7424216.
    2. 1 2 3 Mayor; et al. (2008-06-16). "Trio of 'super-Earths' discovered". BBC News. Retrieved 2008-06-16.
    3. 1 2 M. Mayor; S. Udry; C. Lovis; F. Pepe; D. Queloz; W. Benz; J.-L. Bertaux; F. Bouchy; C. Mordasini; D. Segransan (2009). "The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 Super-Earths (4.2, 6.9, & 9.2 Earth masses)". Astronomy and Astrophysics. 493 (2): 639–644. arXiv: 0806.4587 . Bibcode:2009A&A...493..639M. doi:10.1051/0004-6361:200810451. S2CID   116365802.
    4. Characterizing Extrasolar Planets, Timothy M. Brown, chapter 3, Extrasolar Planets: XVI Canary Islands Winter School of Astrophysics, edited by Hans Deeg, Juan Antonio Belmonte, and Antonio Aparicio, Cambridge, UK: Cambridge University Press, 2007, ISBN   0-521-86808-4.
    5. Barnes, R.; Jackson, B.; Raymond, S.; West, A.; Greenberg, R. (2009). "The HD 40307 Planetary System: Super-Earths or Mini-Neptunes?". The Astrophysical Journal . 695 (2): 1006–1011. arXiv: 0901.1698 . Bibcode:2009ApJ...695.1006B. doi:10.1088/0004-637X/695/2/1006. S2CID   18849636.
    6. Barnes, J.; O'Brien, D. (2002). "Stability of Satellites around Close-in Extrasolar Giant Planets". The Astrophysical Journal . 575 (2): 1087–1093. arXiv: astro-ph/0205035 . Bibcode:2002ApJ...575.1087B. doi:10.1086/341477. S2CID   14508244.