Upsilon Andromedae b

Coordinates: Sky map 01h 36m 47.8s, +41° 24′ 20″
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Upsilon Andromedae b / Saffar
Upsilon Andromedae A
Physical characteristics
Mean radius
~1.8[2]RJ
Mass1.70+0.33
−0.24[1] MJ

Upsilon Andromedae b (υ Andromedae b, abbreviated Upsilon And b, υ And b), formally named Saffar

extrasolar planet approximately 44 light-years away from the Sun in the constellation of Andromeda. The planet orbits its host star, the F-type main-sequence star Upsilon Andromedae A, approximately every five days. Discovered in June 1996 by Geoffrey Marcy and R. Paul Butler, it was one of the first hot Jupiters to be discovered. It is also one of the first non-resolved planets to be detected directly. Upsilon Andromedae b is the innermost-known planet in its planetary system
.

In July 2014 the

Muslim Spain.[6]

Discovery

Upsilon Andromedae b was detected by the variations in its star's

Doppler shift of Upsilon Andromedae's spectrum. The planet's existence was announced in January 1997, together with 55 Cancri b and the planet orbiting Tau Boötis.[7]

Like

semimajor axis of 0.0595 AU.[8]

A limitation of the radial velocity method used to detect Upsilon Andromedae b is that only a lower limit on the

inclination of the orbit. A mass of 1.70 MJ and an inclination of 24° were later found using high-resolution spectroscopy.[1]

Physical characteristics

An artist's impression of Upsilon Andromedae b and its parent star

Given the planet's high mass, it is likely that Upsilon Andromedae b is a gas giant with no solid surface.

The

tidal locked
with the same side always facing Upsilon Andromedae A.

silicates and iron in its upper atmosphere.[10] The cloud deck instead absorbs the star's radiation; between that and the hot, high-pressure gas surrounding the mantle, exists a stratosphere of cooler gas.[11] The outer shell of dark, opaque, hot cloud is assumed to consist of vanadium and titanium oxides, but other compounds like tholins
cannot be ruled out yet.

The chemical elements in the atmosphere can be studied by finding their absorption lines in the thermal spectrum of the planet; given typical planet temperatures, the spectrum has its peak at infrared wavelengths. So far, only water vapor has been detected in this planet, while carbon monoxide and methane are still under the detection limit.[1]

The planet is unlikely to have large moons, since tidal forces would either eject them from orbit or destroy them on short timescales compared to the age of the system.[12]

The planet (with

Planetpol.[13] Preliminary results from polarimetric studies indicate that the planet has a predominately blue color, is 1.36 times as large and 0.74 times as massive as Jupiter, meaning that the mean density is 0.36g/cm3. It has a geometric albedo of 0.35 in visible light.[14] In 2016–2017 the direct detection of the planetary thermal emission was claimed, but the detection was questioned in 2021.[15] Tidal heating models predict a similar mass for the planet.[2]

Host star

Main article: Upsilon Andromedae § Upsilon Andromedae A

The planet orbits a (F-type) star named Titawin (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. 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.

Effect on the parent star

Artist's impression of the hot spot, shown in orange hues

Upsilon Andromedae b appears to be responsible for increased

chromospheric activity on its parent star. Observations suggest that there is a "hot spot" on the star around 169 degrees away from the sub-planetary point. This may be the result of interactions between the magnetic fields of the planet and the star. The mechanism may be similar to that responsible for the activity of RS Canum Venaticorum variable stars, or the interaction between Jupiter and its moon Io.[16]

See also

References

  1. ^
    S2CID 19960378
    .
  2. ^
    S2CID 118409453
    .
  3. ^ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. 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, International Astronomical Union, 15 December 2015.
  6. ^ "NameExoWorlds The Approved Names". Archived from the original on 2018-02-01. Retrieved 2016-01-17.
  7. doi:10.1086/310444
    .
  8. S2CID 119067572. (web version
    )
  9. S2CID 20549014
    .
  10. S2CID 16004653
    .
  11. S2CID 13978248
    .
  12. S2CID 14508244
    .
  13. S2CID 8684361
    .
  14. arXiv:1109.3116 [astro-ph.EP
    ].
  15. S2CID 238198093
  16. S2CID 3043910
    .

External links


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