XO-2
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XO-2 is a binary star system about 490 light-years (150 parsecs) away in the constellation Lynx. It consists of two components, XO-2N and XO-2S, both of which host planetary systems.
Star system
This system is unusual in that the stars are not typically referred to as components A & B, but are designated based on their positions in the sky: XO-2N is the northern star and XO-2S is the southern star.
Both of the stars are slightly cooler than the Sun and are nearly identical to each other. The system has a magnitude of 11 and cannot be seen with the naked eye but is visible through a small telescope. These stars are also notable for their large proper motions.
XO-2N and XO-2S have a separation of approximately 4,600 AU.
Planetary systems
Two planets were reported to orbit around XO-2S in 2014 using the radial velocity method. One of them is Jupiter-mass and another has a mass comparable to Saturn. A 2024 study found evidence for a third, super-Jupiter mass planet around XO-2S.
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥0.26±0.01 MJ | 0.1347±0.0025 | 18.220±0.001 | 0.15±0.02 | — | — |
| c | ≥1.38±0.05 MJ | 0.4737+0.0085 −0.0088 | 120.059±0.013 | 0.149±0.006 | — | — |
| d | ≥3.71+1.2 −0.51 MJ | 5.46+0.85 −0.40 | 4,696+1,133 −489 | 0.091+0.028 −0.018 | — | — |
There is one confirmed exoplanet orbiting XO-2N. XO-2Nb, which is classified as a hot Jupiter, was discovered by the XO Telescope using the transit method around XO-2N in 2007. It was initially the only known planet in the system and was referred to as XO-2b. A long-period variation in the radial velocity of XO-2N was detected in 2015, which could be explained by either a second planet or a stellar activity cycle. The stellar activity explanation is considered more likely, and is further supported by a 2024 study.
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 0.597±0.021 MJ | 0.03668(9) | 2.615859719(54) | <0.006 | 87.47±0.37° | 1.033±0.023 RJ |
See also
Other systems with multiple planet-hosting stars:
Notes
Further reading
- Fernandez, Jose M.; et al. (2009). . The Astronomical Journal. 137 (6): 4911–4916. arXiv:. Bibcode:. doi:. S2CID .
- Narita, Norio; et al. (2011). . Publications of the Astronomical Society of Japan. 63 (6): L67–L71. arXiv:. Bibcode:. doi:. S2CID .
- Sing, D. K.; et al. (2011). . Astronomy and Astrophysics. 527 A73. arXiv:. Bibcode:. doi:. S2CID .
External links
- NASA PlanetQuest:
- . Exoplanets. Archived from on 2016-03-03.