WASP-47

Last updated
WASP-47
Observation data
Epoch J2000       Equinox J2000
Constellation Aquarius
Right ascension 22h 04m 48.7262s [1]
Declination −12° 01′ 07.999″ [1]
Apparent magnitude  (V)11.986
Characteristics
Evolutionary stage Main sequence
Spectral type G9V
Astrometry
Radial velocity (Rv)−26.56(47) [1]  km/s
Proper motion (μ)RA: 15.074(20)  mas/yr [1]
Dec.: −41.467(20)  mas/yr [1]
Parallax (π)3.7010 ± 0.0201  mas [1]
Distance 881 ± 5  ly
(270 ± 1  pc)
Details
Mass 1.11 (± 0.05)  M☉
Radius 1.16 (± 0.26)  R☉
Luminosity ~1.16  L☉
Surface gravity (log g)4.354 (± 0.086)  cgs
Temperature 5576 (± 68)  K
Metallicity [Fe/H]+0.36 (± 0.05)  dex
Rotation 32.5±3.9 d [2]
Age 6.5 +2.6
−1.2  Gyr
Other designations
Gaia DR3  2613413008919918976, K2-23, EPIC  206103150, 2MASS J22044873-1201079, WISE J220448.74-120108.4 [3]
Database references
SIMBAD data

WASP-47 is a star similar in size and brightness to the Sun about 881 light-years away in the constellation Aquarius. It lies within the Kepler K2 campaign field 3. It was first noticed to have a hot Jupiter exoplanet orbiting every 4 days in 2012 by the Wide Angle Search for Planets (WASP) team. [4] While it was thought to be a typical hot Jupiter system, three more planets were found in 2015: [5] [6] an outer gas giant within the habitable zone, a hot Neptune exterior to the hot Jupiter's orbit and a super-Earth interior to the hot Jupiter's orbit. WASP-47 is the only planetary system known to have both planets near the hot Jupiter and another planet much further out. [7]

Contents

Nomenclature and history

Prior to the discovery of its planets, WASP-47 was given the 2MASS designation of 2MASS J22044873-1201079. It was also observed by the Wide-field Infrared Survey Explorer and given the designation WISE J220448.74-120108.4. When observed by NASA's K2 mission, it was given the Ecliptic Plane Input Catalog designation of EPIC 206103150, and later named K2-23 after the discovery of planets d and e.

In 2012, a team from the SuperWASP group, led by Coel Hellier, announced the discovery of a Hot Jupiter exoplanet, with the designation WASP-47b, orbiting every 4.17 days. [4] Three years later in 2015, Neveu-Van Malle et al. found a second planet, WASP-47c, orbiting within the habitable zone of the system using the HARPS spectrograph at the La Silla Observatory in Chile. [6] Using data from NASA's K2 mission a Planet Hunters volunteer discovered multiple planets around WASP-47 [8] and after analysing the data the researchers (Becker et al. 2015) published the two additional transiting planets, the Hot Neptune WASP-47d and the Mega-Earth WASP-47e, orbiting near WASP-47b. [5]

Stellar characteristics

WASP-47 is a G-type main-sequence star of spectral type G9V, making it quite similar to the Sun. It is 1.11 M☉ and 1.16 R☉, with a temperature of 5576 K and an age of about 6.5 billion years. In comparison, the Sun has a slightly higher temperature of 5778 K but is significantly younger, at 4.5 billion years old. [7]

The star is very metal-rich, with a metallicity ([Fe/H]) of about +0.36, or about twice the amount of iron and other elements heavier than Hydrogen and Helium than the Sun. [7] This would explain how two massive gas giants, as well as a Mega-Earth, were able to form around the same star. WASP-47 is estimated to have a luminosity of 1.16 L☉. [9]

The star's apparent magnitude, or how bright it appears from Earth's perspective, is around 12. Therefore, it is far too faint to be seen with the unaided eye.

Planetary system

The WASP-47 planetary system [7] [10] [11]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
e9.0±0.5  M🜨 0.0170.789592 ± 0.0000110.03 +0.036
−0.02		85.98 ± 0.75° 1.810 ± 0.027  R🜨
b363.6 ± 7.3  M🜨 0.0524.1591289 ± 0.00000420.0028 +0.0042
−0.0020		88.98 ± 0.20° 12.64 ± 0.15  R🜨
d15.5±0.8  M🜨 0.0879.03077 ± 0.000170.00600 +0.0098
−0.0041		89.32 ± 0.23° 3.576 ± 0.046  R🜨
c398.9 ± 9.1  M🜨 1.42588.5 ± 2.40.296 ± 0.017——

WASP-47 has a diverse and complex system of four planets. Three of them – e, b, and d – transit the host star, while WASP-47c was found with the radial velocity method. The first three have widely varying sizes, between 1.8 and 13 times the radius of Earth. They are also much more massive than Earth, with the least massive WASP-47e at 6.8 ME. Both gas giants are significantly more massive than Jupiter, at 1.2 and 1.57 MJ, respectively. In comparison, Jupiter is about 318 ME. However, because of observation effects from Earth's turbulent atmosphere, the mass values for all four planets have relatively high uncertainties, with WASP-47c having the greatest uncertainty. Despite that, the compositions for the planets are well-constrained. WASP-47e has almost no volatile materials (water, hydrogen/helium), d has a thin gaseous envelope, and b and c are both gas giants like Jupiter and Saturn. [7]

The presence of two rather small planets, as well as the orbital configuration of the first three planets, is not expected for Hot Jupiter systems, as a migrating gas giant is thought to kick out any small inner planets. In order for the system to come out the way it is now, the two gas giants likely would have to have formed before the lower-mass planets e and d. This is called two-stage planetary formation, and is hypothesized to have happened in the Solar System as well. It is hypothesized that WASP-47b would have moved inwards and brought planet-forming material close to the star. Once most of the gas dissipates, the two gas-poor planets form nearby the large Hot Jupiter. [12]

Planets e, b, and d have very similar orbits, with orbital periods of 0.8, 4.2, and 9.1 days, respectively. All of them are very hot (≥1000 K) [13] and have very low orbital eccentricities, even lower than those of Earth. In stark contrast to the inner planets, c has an eccentric orbit (e = 0.36) lasting over 580 days within the habitable zone of its host star. [7] The high eccentricity can't be explained by the inward migration of WASP-47b, and there isn't any secondary star to cause it. The only likely remaining explanation is that another massive planet altered the orbit of WASP-47c that is either further out in the system or was ejected billions of years ago. [12]

See also

Related Research Articles

<span class="mw-page-title-main">Hot Jupiter</span> Class of high mass planets orbiting close to a star

Hot Jupiters are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods. The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".

<span class="mw-page-title-main">Eccentric Jupiter</span> Jovian planet that orbits its star in an eccentric orbit

An eccentric Jupiter is a Jovian planet that orbits its star in an eccentric orbit. Eccentric Jupiters may disqualify a planetary system from having Earth-like planets in it, because a massive gas giant with an eccentric orbit may eject all Earth mass exoplanets from the habitable zone, if not from the system entirely.

<span class="mw-page-title-main">Gliese 876 c</span> Gas giant orbiting Gliese 876

Gliese 876 c is an exoplanet orbiting the red dwarf Gliese 876, taking about 30 days to complete an orbit. The planet was discovered in April 2001 and is the second planet in order of increasing distance from its star.

<span class="mw-page-title-main">Gliese 876 b</span> Extrasolar planet orbiting Gliese 876

Gliese 876 b is an exoplanet orbiting the red dwarf Gliese 876. It completes one orbit in approximately 61 days. Discovered in June 1998, Gliese 876 b was the first planet to be discovered orbiting a red dwarf.

Upsilon Andromedae d, formally named Majriti, is a super-Jupiter exoplanet orbiting within the habitable zone of the Sun-like star Upsilon Andromedae A, approximately 44 light-years away from Earth in the constellation of Andromeda. Its discovery made it the first multiplanetary system to be discovered around a main-sequence star, and the first such system known in a multiple star system. The exoplanet was found by using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object.

An ultra-short period (USP) planet is a type of exoplanet with an orbital period of less than one Earth day. At this short distance, tidal interactions lead to relatively rapid orbital and spin evolution. Therefore when there is a USP planet around a mature main-sequence star it is most likely that the planet has a circular orbit and is tidally locked. There are not many USP planets with sizes exceeding 2 Earth radii. About one out of 200 Sun-like stars has an ultra-short-period planet. There is a strong dependence of the occurrence rate on the mass of the host star. The occurrence rate falls from % for M dwarfs to % for F dwarfs. Mostly the USP planets seem consistent with an Earth-like composition of 70% rock and 30% iron, but K2-229b has a higher density suggesting a more massive iron core. WASP-47e and 55 Cnc e have a lower density and are compatible with pure rock, or a rocky-iron body surrounded by a layer of water.

<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.

This page describes exoplanet orbital and physical parameters.

<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 1 May 2024, there are 5,662 confirmed exoplanets in 4,169 planetary systems, with 896 systems having more than one planet. This is a list of the most notable discoveries.

Kepler-47 is a binary star system in the constellation Cygnus located about 3,420 light-years away from Earth. The stars have three exoplanets, all of which orbit both stars at the same time, making this a circumbinary system. The first two planets announced are designated Kepler-47b, and Kepler-47c, and the third, later discovery is Kepler-47d. Kepler-47 is the first circumbinary multi-planet system discovered by the Kepler mission. The outermost of the planets is a gas giant orbiting within the habitable zone of the stars. Because most stars are binary, the discovery that multi-planet systems can form in such a system has impacted previous theories of planetary formation.

<span class="mw-page-title-main">Kepler-47c</span> Goldilocks gas giant orbiting Kepler-47 system

Kepler-47c is an exoplanet orbiting the binary star system Kepler-47, the outermost of three such planets discovered by NASA's Kepler spacecraft. The system, also involving two other exoplanets, is located about 3,400 light-years away.

<span class="mw-page-title-main">Kepler-47b</span> Circumbinary gas giant exoplanet orbiting the Kepler-47 star system

Kepler-47b is an exoplanet orbiting the binary star system Kepler-47, the innermost of three such planets discovered by NASA's Kepler spacecraft. The system, also involving two other exoplanets, is located about 3,400 light-years away.

<span class="mw-page-title-main">K2-3d</span> Mini-Neptune orbiting K2-3

K2-3d, also known as EPIC 201367065 d, is a confirmed exoplanet of probable mini-Neptune type orbiting the red dwarf star K2-3, and the outermost of three such planets discovered in the system. It is located 143 light-years away from Earth in the constellation of Leo. 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. It was the first planet in the Kepler "Second Light" mission to receive the letter "d" designation for a planet. Its discovery was announced in January 2015.

Kepler-419c is a super-Jupiter exoplanet orbiting within the habitable zone of the star Kepler-419, the outermost of two such planets discovered by NASA's Kepler spacecraft. It is located about 3,400 light-years from Earth in the constellation Cygnus. The exoplanet was found by using the transit timing variation method, in which the variations of transit data from an exoplanet are studied to reveal a more distant companion.

K2-141b is a massive rocky exoplanet orbiting extremely close to a K Type orange main-sequence star K2-141. The planet was first discovered by the Kepler space telescope during its K2 “Second Light” mission and later observed by the HARPS-N spectrograph. It is classified as an Ultra-short Period (USP) and is confirmed to be terrestrial in nature. Its high density implies a massive iron core taking up between 30% and 50% of the planet's total mass.

References

  1. 1 2 3 4 5 6 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. ↑ Bryant, Edward M.; Bayliss, Daniel (2022), "Revisiting WASP-47 with ESPRESSO and TESS", The Astronomical Journal, 163 (5): 197, arXiv: 2202.12747 , Bibcode:2022AJ....163..197B, doi: 10.3847/1538-3881/ac58ff , S2CID   247154656
  3. ↑ "WASP-47". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2024-04-13.
  4. 1 2 Hellier, Coel; et al. (2012). "Seven transiting hot Jupiters from WASP-South, Euler and TRAPPIST: WASP-47b, WASP-55b, WASP-61b, WASP-62b, WASP-63b, WASP-66b and WASP-67b". Monthly Notices of the Royal Astronomical Society. 426 (1): 739–750. arXiv: 1204.5095 . Bibcode: 2012MNRAS.426..739H . doi: 10.1111/j.1365-2966.2012.21780.x .
  5. 1 2 Becker, Juliette C.; Vanderburg, Andrew; Adams, Fred C.; Rappaport, Saul A.; Schwengeler, Hans Martin (2015-10-12). "Wasp-47: A Hot Jupiter System with Two Additional Planets Discovered by K2". The Astrophysical Journal. 812 (2): L18. arXiv: 1508.02411 . Bibcode:2015ApJ...812L..18B. doi:10.1088/2041-8205/812/2/L18. ISSN   2041-8213. S2CID   14681933.
  6. 1 2 Neveu-VanMalle, M.; et al. (2016). "Hot Jupiters with relatives: Discovery of additional planets in orbit around WASP-41 and WASP-47". Astronomy and Astrophysics. 586 A93. arXiv: 1509.07750 . Bibcode: 2016A&A...586A..93N . doi: 10.1051/0004-6361/201526965 . S2CID   53354547.
  7. 1 2 3 4 5 6 "WASP-47". exoplanetarchive.ipac.caltech.edu.
  8. ↑ Zooniverse, The (2015-11-04). "Hot Friends of Hot Jupiters: The WASP-47 system". Planet Hunters. Retrieved 2020-02-11.
  9. ↑ "HEC: Exoplanets Calculator - Planetary Habitability Laboratory @ UPR Arecibo". phl.upr.edu. Archived from the original on 2021-10-18. Retrieved 2017-11-19.
  10. ↑ Vanderburg, Andrew; et al. (2017-11-16). "Precise Masses in the WASP-47 System". The Astronomical Journal. 154 (6) 237. arXiv: 1710.00026 . Bibcode: 2017AJ....154..237V . doi: 10.3847/1538-3881/aa918b . S2CID   54750116.
  11. ↑ Nascimbeni, V.; et al. (2023). "A new dynamical modeling of the WASP-47 system with CHEOPS observations". Astronomy and Astrophysics. 673 A42. arXiv: 2302.01352 . Bibcode: 2023A&A...673A..42N . doi: 10.1051/0004-6361/202245486 .
  12. 1 2 "weiss". Archived from the original on 2017-12-01. Retrieved 2017-11-19.
  13. ↑ "ExoFOP 206103150". exofop.ipac.caltech.edu. Archived from the original on 2022-08-24. Retrieved 2017-11-19.
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