Kepler-37d

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]

Kepler-37d

Discovery[1]
Discovery site	Kepler space telescope
Discovery date	2013
Detection method	Transit
Orbital characteristics[2]
Semi-major axis	0.2109±0.0030 AU
Eccentricity	<0.10
Orbital period (sidereal)	39.7922622(65) d
Inclination	89.335°+0.043° −0.047°
Star	Kepler-37
Physical characteristics[2]
Mean radius	2.030+0.030 −0.039 R🜨
Mass	5.4±1.4 M🜨[3] or <2.0 M🜨[2]
Mean density	4.29+0.52 −0.74 g/cm3[3] or <1.3 g/cm3[2]
Temperature	499±7 K (226 °C; 439 °F, equilibrium)

A 2021 study detected Kepler-37d via radial velocity, finding a mass of about 5.4 M_🜨,^[3] but a 2023 study instead found an upper limit on its mass of only 2 M_🜨.^[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]

Host star

Main article: Kepler-37

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.

See also

• List of planets discovered by the Kepler spacecraft