Kepler-37d is an exoplanet discovered by the Kepler space telescope in February 2013.[4] It is located 209 light years away,[5] in the constellation Lyra.[4] With an orbital period of 39.8 days,[3] it is the largest of the three known planets orbiting its parent star Kepler-37.[6]
A 2021 study detected Kepler-37d via radial velocity, finding a mass of about 5.4 ME,[3] but a 2023 study instead found an upper limit on its mass of only 2 ME.[2] In either case, it is not a rocky planet, but a low-density planet rich in volatiles.
In 2015, a grant was approved to further expand the Sagan Planet Walk by installing a Kepler-37d station on the Moon 384,500 kilometers (238,900 mi) away.[7][8]
The planet orbits a (G-type) star similar to the Sun, named Kepler-37, orbited by a total of four planets. The star has a mass of 0.80 M☉ and a radius of 0.79 R☉. It has a temperature of 5417 K and is 5.66 billion years old. In comparison, the Sun is 4.6 billion years old,[9] and has a temperature of 5778 K.[10]
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 9.71. Therefore, it is too dim to be seen with the naked eye.
^ abcdRajpaul, V. M.; Buchhave, L. A.; Lacedelli, G.; Rice, K.; Mortier, A.; Malavolta, L.; Aigrain, S.; Borsato, L.; Mayo, A. W.; Charbonneau, D.; Damasso, M.; Dumusque, X.; Ghedina, A.; Latham, D. W.; López-Morales, M.; Magazzù, A.; Micela, G.; Molinari, E.; Pepe, F.; Piotto, G.; Poretti, E.; Rowther, S.; Sozzetti, A.; Udry, S.; Watson, C. A. (2021), "A HARPS-N mass for the elusive Kepler-37d: A case study in disentangling stellar activity and planetary signals", Monthly Notices of the Royal Astronomical Society, 507 (2): 1847–1868, arXiv:2107.13900, doi:10.1093/mnras/stab2192
