HD 37124 and Its Three Known Planets

HD 37124 is a G4 V star located 103 light-years away. This spectral type identifies it as a main-sequence dwarf of the same broad temperature class as the Sun, though its reported temperature of 5490 K is cooler than the Sun's. Its reported mass of 0.75 solar masses is likewise smaller than the Sun's, while its radius measures 1 solar radius. The star's age is given as a reported lower limit of 13 billion years. Three planets orbit this host: HD 37124 b, HD 37124 c, and HD 37124 d.

All three planets were found by the radial velocity method, which measures the wobble a planet's gravity induces in its star's motion; repeated wobbles reveal the planet and its orbital period. HD 37124 b was discovered in 2002 and has a minimum mass of 215 Earth masses, completing an orbit in 154 days. HD 37124 c, also discovered in 2002, has a minimum mass of 207 Earth masses and an orbital period of 886 days. HD 37124 d, discovered in 2005, has a minimum mass of 221 Earth masses and an orbital period of 1860 days. A minimum mass is a lower bound on a planet's true mass, so each of these values sets a floor rather than an exact figure. Each planet's minimum mass is larger than Earth's.

Among these planets, the orbital periods differ considerably. HD 37124 b has the shortest year by reported estimates, at 154 days, while HD 37124 c has the second-shortest, at 886 days, and HD 37124 d has the longest, at 1860 days. Their minimum masses also span a range: HD 37124 c has the smallest minimum mass, at 207 Earth masses, HD 37124 b has the second-smallest, at 215 Earth masses, and HD 37124 d has the largest, at 221 Earth masses.