Upsilon Andromedae d

Coordinates: Sky map 01h 36m 47.8s, +41° 24′ 20″
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Upsilon Andromedae d / Majriti
Discovery
Upsilon Andromedae A
Physical characteristics
Mean radius
~1.02 RJ
Mass10.25+0.7
−3.3[2] MJ
Temperature218 K (−55 °C; −67 °F)

Upsilon Andromedae d (υ Andromedae d, abbreviated Upsilon And d, υ And d), formally named Majriti

Doppler shifts of spectral lines
of the host star suggest an orbiting object.

Name

In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.[3] The process involved public nomination and voting for the new names.[4] In December 2015, the IAU announced the planet would be named "Majriti".[5] The winning name was submitted by the Vega Astronomy Club of Morocco, honoring the 10th-century scientist Maslama al-Majriti.[6]

Characteristics

Mass, radius and temperature

An artist's impression of UpsilonAnd d

Upsilon Andromedae d is a super-Jupiter, an exoplanet that has a mass larger than that of the planet Jupiter. It has a temperature of 218 K (−55 °C; −67 °F).[7] It has a mass of 10.25 MJ[2] and a likely radius of around 1.02 RJ based on its mass.[citation needed]

Host star

Main article: Upsilon Andromedae § Upsilon Andromedae A

The planet orbits a (F-type) star named Upsilon Andromedae A. The star has a mass of 1.27 M☉ and a radius of around 1.48 R☉. It has a temperature of 6,074 K and is 3.12 billion years old. In comparison, the Sun is about 4.6 billion years old[8] and has a temperature of 5,778 K.[9] The star is slightly metal-rich, with a metallicity ([Fe/H]) of 0.09, or about 123% of the solar amount. Its luminosity (L☉) is 3.57 times that of the Sun.

The star's apparent magnitude, or how bright it appears from Earth's perspective, is 4.09. Therefore, Upsilon Andromedae can be seen with the naked eye.

Orbit

Upsilon Andromedae d orbits its star nearly every 3.5 years (about 1,276 days) in an

eccentric orbit, more eccentric than that of any of the known planets in the Solar System.[10] To explain the planet's orbital eccentricity, some have proposed a close encounter with a now-lost outer planet of Upsilon Andromedae A. The encounter would have moved planet "d" into an eccentric orbit closer to the star and ejected the outer planet.[11][12]

Habitability

habitable exomoon
orbiting a gas giant
See also: Habitability of natural satellites

While Upsilon Andromedae d is likely a gas giant and therefore uninhabitable, it may have a moon or moons that are habitable.

The planet lies in the habitable zone of Upsilon Andromedae A as defined both by the ability for an Earthlike world to retain

ultraviolet radiation received from the star.[13]

For a stable orbit, the ratio between a moon's orbital period Ps around its primary and that of the primary (planet) around its star Pp must be < 1/9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days.[14][15] Simulations suggest that a moon with an orbital period less than about 45 to 60 days will remain safely bound to a massive giant planet or brown dwarf that orbits 1 AU from a Sun-like star.[16] In the case of Upsilon Andromedae d, the orbital period would have to be no greater than 120 days (around 4 months) in order to have a stable orbit.

Discovery and further studies

Upsilon Andromedae d was detected by measuring variations in its star's

Doppler shift of the spectrum of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the hot Jupiter Upsilon Andromedae b
; however, by 1999, it was clear that the inner planet could not explain the velocity curve.

In 1999, astronomers at both

Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data.[17] The two new planets were designated Upsilon Andromedae c
and Upsilon Andromedae d.

Preliminary

astrometric measurements suggest the orbit of Upsilon Andromedae d may be inclined at 155.5° to the plane of the sky.[18] However, these measurements were later proved useful only for upper limits,[19] and contradict even the inner planet υ And b's inclination of >30°. The mutual inclination between c and d meanwhile is 29.9 degrees.[2] The true inclination of Upsilon Andromedae d was determined as 23.8° after combined results were measured from the Hubble Space Telescope and radial velocity measurements.[2]

When it was discovered, a limitation of the radial velocity method used to detect Upsilon Andromedae d is that the orbital inclination is unknown, and only a lower limit on the planet's

mass of the planet, which is about 10.25 times the mass of Jupiter.[2]

See also

References

  1. ^
    S2CID 10934982. Archived
    from the original on 2019-12-09. Retrieved 2021-10-28.
  2. ^
    S2CID 120127162. Archived
    (PDF) from the original on 2011-06-10. Retrieved 2010-05-25.
  3. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars Archived 2017-09-04 at the Wayback Machine. IAU.org. 9 July 2014
  4. ^ "NameExoWorlds The Process". Archived from the original on 2015-08-15. Retrieved 2015-09-05.
  5. ^ Final Results of NameExoWorlds Public Vote Released Archived 2017-12-02 at the Wayback Machine, International Astronomical Union, 15 December 2015.
  6. ^ "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2016-01-17.
  7. ^ "ups And d (F-Warm Jovian)". hpcf.upr.edu. May 2014. Archived from the original on 2016-08-21. Retrieved 2016-08-07.
  8. ^ Cain, Fraser (16 September 2008). "How Old is the Sun?". Universe Today. Archived from the original on 18 August 2010. Retrieved 19 February 2011.
  9. ^ Cain, Fraser (September 15, 2008). "Temperature of the Sun". Universe Today. Archived from the original on 29 August 2010. Retrieved 19 February 2011.
  10. S2CID 119067572. (web version Archived 2019-03-05 at the Wayback Machine
    )
  11. S2CID 4324250
    .
  12. S2CID 17096607
    .
  13. S2CID 2241081
    .
  14. S2CID 14754293
    .
  15. S2CID 118458061
    .
  16. ^ LePage, Andrew J. "Habitable Moons:What does it take for a moon — or any world — to support life?". SkyandTelescope.com. Archived from the original on 2012-04-06. Retrieved 2011-07-11.
  17. doi:10.1086/308035
    .
  18. doi:10.1086/318927. Archived
    from the original on 2015-11-06. Retrieved 2009-03-09.
  19. S2CID 378792
    .


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