Aldebaran b

Short description: Jovian planet candidate orbiting Aldebaran

Aldebaran bDiscovery

Discovery date| 1993 (dubious)
May 15, 2015 (confirmed)

Detection method

| Radial velocity
Orbital characteristics
astron|astron|helion}}| 1.606 +0.2105−0.2375 AU
astron|astron|helion}}| 1.314 +0.3295−0.3025 AU

Semi-major axis

| 1.46 ± 0.27 AU (218,000,000 ± 40,000,000 km)
Eccentricity| 0.1 ± 0.05
Orbital period| 628.96 ± 0.9 d
astron|astron|helion}}| 1999/04/28 ± 50

astron|astron|helion}}

| 287 ± 29
Star| Aldebaran
Physical characteristics
Mass| >5.8±0.7[1] |♃|J}}}}}}
Physics| 1,500 K (1,230 °C; 2,240 °F)

Aldebaran b is a candidate exoplanet orbiting the orange giant star Aldebaran, 65 light-years away. It was initially detected in 1993, but was considered doubtful until 2015, when researchers came to a conclusion that there is likely an exoplanet orbiting Aldebaran, consistent with the original calculations, but also compatible with stellar activity.[2] However, in 2019, new data placed doubts on its existence again.[3]

## Contents

* 1 Physical properties
* 1.1 Mass and orbit
* 1.2 Host star
* 2 Discovery
* 2.1 1993 proposal
* 2.2 2015 confirmed status
* 2.3 2019 doubts on existence
* 3 See also
* 4 References
* 5 External links

## Physical properties

### Mass and orbit

Aldebaran b is a giant exoplanet with at least 5.8 times the mass of Jupiter. It orbits at a distance about 45% farther than Earth does from the Sun. The equilibrium temperature of this planet is likely to be around 1,500 K (1,230 °C; 2,240 °F), as it is strongly irradiated by its giant host star. Nevertheless, when Aldebaran was a main sequence star, it is likely that the planet had an equilibrium temperature comparable to that of the Earth.[1]

### Host star

Main article: Astronomy:Aldebaran

The host star, Aldebaran, is an orange giant star, meaning it has moved off from the main sequence and exhausted the supply of hydrogen in the core. It has a spectral class of K5 III.[4]

Aldebaran is a K-type star that is 1.16 ± 0.07 times the mass[1] and 44 times the radius of the Sun. It has a surface temperature of 3,910 K. In comparison, the Sun has a surface temperature of 5778 K.[5]

The star's average apparent magnitude, or how bright it usually appears from Earth, is 0.86, easily visible to the naked eye.

## Discovery

### 1993 proposal

The exoplanet was first proposed in 1993, radial velocity measurements of Aldebaran, Arcturus and Pollux showed that Aldebaran exhibited a long-period radial velocity oscillation, which could be interpreted as a substellar companion. The measurements for Aldebaran implied a companion with a minimum mass 11.4 times that of Jupiter in a 643-day orbit at a separation of 2.0 AU (300 Gm) in a mildly eccentric orbit. However, all three stars surveyed showed similar oscillations yielding similar companion masses, and the authors concluded that the variation was likely to be intrinsic to the star rather than due to the gravitational effect of a companion.[6]

### 2015 confirmed status

In 2015, a study showed stable long-term evidence for both a planetary companion and stellar activity.[7]

### 2019 doubts on existence

In 2019, an analysis of additional data provided by Lick Observatory has placed the existence of Aldebaran b in serious doubt, because of apparent phase jitter of radial-velocity signal; a better data fit is obtained by either two planets or no planets at all around Aldebaran.[3]

## See also

* Alpha Centauri Bb
* Proxima Centauri b
* Hot Jupiter

## References

1. ↑ 1.0 1.1 1.2 Farr, W. (2018). "Aldebaran b's temperate past uncovered in planet search data". The Astrophysical Journal 865 (2): L20. doi:10.3847/2041-8213/aadfde. Bibcode: 2018ApJ...865L..20F.
2. ↑ Hatzes, A.P. (May 15, 2015). "Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity". Astronomy & Astrophysics 580: 18. doi:10.1051/0004-6361/201425519. Bibcode: 2015yCat..35800031H.
3. ↑ 3.0 3.1 Reichert, Katja (25 March 2019). "Precise radial velocities of giant stars XII. Evidence against the proposed planet Aldebaran b". Astronomy & Astrophysics A22: 625. doi:10.1051/0004-6361/201834028. Bibcode: 2019A&A...625A..22R.
4. ↑ Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal 132 (1): 161–170. doi:10.1086/504637. Bibcode: 2006AJ....132..161G.
5. ↑ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. http://www.universetoday.com/18092/temperature-of-the-sun/.
6. ↑ Hatzes, A.; Cochran, W. (1993). "Long-period radial velocity variations in three K giants". The Astrophysical Journal 413 (1): 339–348. doi:10.1086/173002. Bibcode: 1993ApJ...413..339H.
7. ↑ Hatzes, A. P. et al. (2015). "Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity". Astronomy & Astrophysics 580: A31. doi:10.1051/0004-6361/201425519. Bibcode: 2015A&A...580A..31H.

## External links

* Aldebaran b at the Extrasolar Planet Encyclopedia

* v
* t
* e

Exoplanetology

* Planet
* Definition
* IAU
* Planetary science

Main topics|

* Exoplanet
* Methods of detecting exoplanets
* Planetary system

Sizes
and types|

| Terrestrial|

* Carbon planet
* Coreless planet
* Desert planet
* Dwarf planet
* Ice planet
* Iron planet
* Lava planet
* Mega-Earth
* Ocean planet
* Sub-Earth
* Super-Earth

|

Gaseous|

* Eccentric Jupiter
* Gas dwarf
* Helium planet
* Hot Jupiter
* Hot Neptune
* Ice giant
* Mini-Neptune
* Super-Neptune
* Super-Jupiter

Other types|

* Brown dwarf
* Chthonian planet
* Circumbinary planet
* Disrupted planet
* Double planet
* Eyeball planet
* Mesoplanet
* Planemo
* Planet/Brown dwarf boundary
* Planetesimal
* Protoplanet
* Pulsar planet
* Sub-brown dwarf
* Ultra-cool dwarf
* Ultra-short period planets (USP)

Formation
and evolution|

* Accretion
* Accretion disk
* Asteroid belt
* Circumplanetary disk
* Circumstellar disc
* Circumstellar envelope
* Cosmic dust
* Debris disk
* Detached object
* Disrupted planet
* Excretion disk
* Exoplanetary Circumstellar Environments and Disk Explorer
* Exozodiacal dust
* Extraterrestrial materials
* Extraterrestrial sample curation
* Giant-impact hypothesis
* Gravitational collapse
* Hills cloud
* Interplanetary dust cloud
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* Interplanetary space
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* Oort cloud
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* Planetary migration
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* Planetesimal
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* Protoplanetary disk
* Ring system
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* Scattered disc
* Star formation

Systems|

* Exocomet
* Exomoon
* Interstellar comet
* Mean-motion resonances
* Retrograde planet
* Rogue planet
* Tidally detached exomoon
* Titius–Bode laws
* Trojan planet

Host stars|

* A
* B
* Binary star
* Brown dwarfs
* Extragalactic planet
* F/Yellow-white dwarfs
* G/Yellow dwarfs
* Herbig Ae/Be
* K/Orange dwarfs
* M/Red dwarfs
* Planets in globular clusters
* Pulsar
* Red giant
* Subdwarf B
* Subgiant
* T Tauri
* White dwarfs
* Yellow giants

Detection|

* Astrometry
* Direct imaging
* list
* Microlensing
* list
* Polarimetry
* Pulsar timing
* list
* Radial velocity
* list
* Transit method
* list
* Transit-timing variation

Habitability|

* Astrobiology
* Circumstellar habitable zone
* Earth analog
* Extraterrestrial liquid water
* Habitability of natural satellites
* Superhabitable planet

Catalogues|

* Catalog of Nearby Habitable Systems
* Exoplanet Data Explorer
* Extrasolar Planets Encyclopaedia
* NASA Exoplanet Archive
* NASA Star and Exoplanet Database

Lists|

* Exoplanetary systems
* Host stars
* Multiplanetary systems
* Stars with proplyds
* Exoplanets
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* before 2000
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Other|

* Carl Sagan Institute
* Exoplanet phase curves
* Nexus for Exoplanet System Science
* Planets in science fiction
* Sudarsky's gas giant classification

* Discoveries of exoplanets
* Search projects

* v
* t
* e

2015 in space

* « 2014

2016 »

Launches|

| Space probes|

* LISA Pathfinder
* SMAP

|

Space observatories|

* Astrosat
* DSCOVR

Impact events|

* 2015 Kerala meteorite
* 2015 Thailand bolide
* WT1190F impact

Selected comets|

* 15P/Finlay
* C/2014 Q2 (Lovejoy)
* 88P/Howell
* 22P/Kopff
* 10P/Tempel
* C/2013 US10

Selected NEOs|

* Closest asteroid approaches in 2015
* 2015 BP513
* (357439) 2004 BL86
* 2015 AZ43
* 1566 Icarus
* 2015 TB145
* 2007 VE191
* (33342) 1998 WT24
* (85989) 1999 JD6
* 2015 SO2

Exoplanets|

* Aldebaran b
* β Circini b
* EPIC 2037 b
* EPIC 2037 c
* Gliese 1132 b
* HD 155233 b
* HD 164595 b
* HD 219134 b
* HD 219134 c
* HD 219134 d
* HD 219134 e
* HD 219134 f
* HD 219134 g
* HD 219134 h
* HIP 11915 b
* KELT-4Ab
* Kepler-438b
* Kepler-440b
* Kepler-442b
* Kepler-444
* Kepler-451b
* Kepler-452b
* Kepler-453b
* K2-3d
* K2-18b
* K2-22b
* WASP-121b
* Wolf 1061c

Discoveries|

* GW150914 (first observation of gravitational waves, announced in 2016)
* GW151226 (announced in 2016)
* 2015 TH367 (TNO)
* WISE J224607.57−052635.0 (galaxy)

Space
exploration|

* Dawn (Ceres orbit injection)
* Rosetta (orbiting comet 67P)
* MESSENGER (end of mission)
* New Horizons (flyby of Pluto)
* Akatsuki (Venus orbit injection)

* Category:2014 in space — Category:2015 in space — Category:2016 in space

Coordinates:  04h 35m 55.2s, 16° 30′ 33″

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