The designationGJ 3470 comes from theGliese Catalogue of Nearby Stars. This star was first included in theThird Catalogue of Nearby Stars, published in 1991 byGliese andJahreiß, hence theGJ prefix usually used for this star.[9]
In August 2022, GJ 3470 and its planet were included among 20 planetary systems to be named by the thirdNameExoWorlds project.[10] The approved names, proposed by a team fromThailand, were announced in June 2023. GJ 3470 is named Kaewkosin and its planet is named Phailinsiam, after names of precious stones in theThai language.[7]
The star has a mass of 0.539 solar masses, a radius of 0.547 solar radii, and a temperature of about 3,652 K (3,379 °C; 6,114 °F).[3] It is about 0.3-3 billion years old, with a metallicity of 0.2 Fe/H and a rotation period of 21.54 days.[6] The star exhibits strong stellar activity, with three ultraviolet flares detected by 2021.[11]
At least one exoplanet has been discovered orbiting GJ 3470 at a distance of 0.035 astronomical units. The exoplanet, which is calledGJ 3470 b, is ahot Neptune with an orbital period of 3.3 days. It was discovered in 2012 usingradial velocity observations fromHARPS, andtransit observations fromTRAPPIST.[12][13] The planet's atmosphere has been studied in detail, finding it to be composed mainly ofhydrogen andhelium, withRayleigh scattering having been observed.[14] GJ 3470 b is losing mass to its star at a rate of about1010g/s.[15]
In July 2020, a group of amateur astronomers reported a new exoplanet candidate in anarXivpreprint, which they hypothesized to be the size of Saturn and inside the system's habitable zone, along with twelve tentative transits from not yet characterized exoplanets in the same star system.[17][18] If confirmed, GJ 3470 c would become the second exoplanet discovered by amateur astronomers, afterKPS-1b, an exoplanet discovered by Ural State Technical University using amateur data.[19] The new GJ 3470 candidate was discovered with amateur data and through a project led by amateur astronomers.[17][20][21][22][23][24][25] However, it is important to note that the study in question has not been published in any scientific journal, nor has it been peer reviewed.
Similarly, on 21 April 2023, the same group of amateur astronomers reported two new exoplanet candidates co-orbiting, in ahorseshoe exchange orbit, close to the star.[26] If confirmed, this would be the first ever discovery of co-orbiting exoplanets. However, again, the study in question is only in preprint form on arXiv, and it has not been peer reviewed and published in a respected scientific journal.[27][28]
As reported in a follow-up arXiv paper also by amateur astronomers, data fromTESS rules out the existence of all three of these claimed planets. Thus, the "transits" observed by the amateur group were likely caused byvisual artifacts.Radial velocity data can also rule out planets of the expected mass at the claimed periods, suggesting that if the claimed planets did exist, they would have very low densities.[29]
Unrelated to the previous amateur claims, the results of a search fortrojan companions of 95transiting exoplanets by the TROY project were published inAstronomy & Astrophysics in 2024. One strong candidate was identified by this project - a possible2.6±0.7 M🜨 trojan of GJ 3470 b orbiting at its L5Lagrange point, based onradial velocity data. However, no transits of this candidate were detected, indicating that if it transits its radius cannot be larger than that of Earth.[30]
^Bourrier, V.; Dos Santos, L. A.; Sanz-Forcada, J.; García Muñoz, A.; Henry, G. W.; Lavvas, P.; Lecavelier, A.; López-Morales, M.; Mikal-Evans, T.; Sing, D. K.; Wakeford, H. R.; Ehrenreich, D. (2021), "The Hubble PanCET program: Long-term chromospheric evolution and flaring activity of the M dwarf host GJ 3470",Astronomy & Astrophysics,650: A73,arXiv:2103.09864,Bibcode:2021A&A...650A..73B,doi:10.1051/0004-6361/202140487,S2CID232269667
^Benneke, Björn; Knutson, Heather A.; Lothringer, Joshua; Crossfield, Ian J.M.; Moses, Julianne I.; Morley, Caroline; Kreidberg, Laura; Fulton, Benjamin J.; Dragomir, Diana; Howard, Andrew W.; Wong, Ian; Désert, Jean-Michel; McCullough, Peter R.; Kempton, Eliza M.-R.; Fortney, Jonathan; Gilliland, Ronald; Deming, Drake; Kammer, Joshua (2019). "A sub-Neptune exoplanet with a low-metallicity methane-depleted atmosphere and Mie-scattering clouds".Nature Astronomy.3 (9):813–821.arXiv:1907.00449.Bibcode:2019NatAs...3..813B.doi:10.1038/s41550-019-0800-5.S2CID256707037.
^Bourrier, V.; Lecavelier Des Etangs, A.; Ehrenreich, D.; Sanz-Forcada, J.; Allart, R.; Ballester, G. E.; Buchhave, L. A.; Cohen, O.; Deming, D.; Evans, T. M.; García Muñoz, A.; Henry, G. W.; Kataria, T.; Lavvas, P.; Lewis, N.; López-Morales, M.; Marley, M.; Sing, D. K.; Wakeford, H. R. (2018). "Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470b".Astronomy & Astrophysics.620: A147.arXiv:1812.05119.Bibcode:2018A&A...620A.147B.doi:10.1051/0004-6361/201833675.S2CID239583863.
^abScott, Phillip; Walter, Bradley; Ye, Quanzhi; Mitchell, David; Heiland, Leo; Gao, Xing; Palado, Alejandro; Otabek, Burkhonov; Casal, Jesus Delgado; Hill, Colin; Garcia, Alberto (2020-07-14). "GJ 3470 c: A Saturn-like Exoplanet Candidate in the Habitable Zone of GJ 3470".arXiv:2007.07373 [astro-ph.EP].
^Tarrants, Thomas; Li, Andrew (May 2023). "No Evidence for Additional Planets at GJ 3470 from TESS and Archival Radial Velocities".arXiv:2305.02551 [astro-ph.EP].
