HAT-P-29, also known as Muspelheim since 2019 (as part of the IAU's NameExoWorlds project), is a star about 1,040 light-years (320 parsecs) away. It is an F-type main-sequence star. The star's age of 2.2±1.0 billion years is less than half that of the Sun. HAT-P-29 is slightly enriched in heavy elements, having 35% more iron than the Sun.

A very faint 19th-magnitude stellar companion was detected in 2016 at a projected separation of 3.290±0.002″, but Gaia DR2 astrometry suggests that this is an unrelated background object.

Planetary system

In 2011 a transiting hot Jupiter planet, HAT-P-29b, was detected on a mildly eccentric orbit. The planet was named "Surt" by Denmark in 2019. The planetary orbit is likely aligned with the equatorial plane of the star, with a misalignment equal to 26±16 degrees.

The HAT-P-29 planetary system
Companion (in order from star)MassSemimajor axis (AU)Orbital period (days)EccentricityInclinationRadius
b (Surt)0.767+0.046 −0.045 MJ0.0665±0.00125.723376±0.0000210.073+0.029 −0.02888.06+0.78 −0.59°1.055+0.079 −0.072 RJ