TrES-3b / Umbäässa

Size comparison of TrES-3b with Jupiter.
Discovery
Discovered by	O'Donovan et al.
Discovery site	United States
Discovery date	2007
Detection method	Transit
Orbital characteristics
Semi-major axis	0.0226 ± 0.0013 AU (3,380,000 ± 190,000 km)
Orbital period (sidereal)	1.30619 ± 0.00005 d
Inclination	82.15
Star	GSC 03089-00929
Physical characteristics
Mean radius	1.341 ± 0.081 RJ
Mass	1.92 ± 0.23 MJ
Mean density	1,172 kg/m3 (1,975 lb/cu yd)
Surface gravity	2.7 g
Temperature	1555 K[1]

TrES-3b is an extrasolar planet orbiting the star GSC 03089-00929. It has an orbital period of just 31 hours and nearly twice the mass of Jupiter.

The planet TrES-3b is named Umbäässa. The name was selected in the NameExoWorlds campaign by Liechtenstein, during the 100th anniversary of the IAU. In the local dialect of southern Liechtenstein, Umbäässa is a small and barely visible ant.^[2][3]

Discovery

It is the third transiting planet found by the Trans-Atlantic Exoplanet Survey. It was discovered in the constellation Hercules about 10 degrees west of Vega, the brightest star in the summer skies.

Transits in front of the star GSC 03089-00929 were detected by two 10 cm telescopes operating out of Palomar and Lowell Observatories. Transits of TrES-3 were also independently observed by the Hungarian Automated Telescope Network. Seven high-precision radial velocity measurements were made using the HIRES spectrometer at W. M. Keck Observatory, which confirmed the presence of a planetary mass companion with a minimum mass twice that of the planet Jupiter.^[4]

Characteristics

The planet's home star is slightly smaller and cooler than the Sun. The orbital period is less than one and a third days, one of the shortest known.^[4] Despite close proximity to the star, no evidence of tidal-driven orbital decay was present as in 2020, with best data fit indicating only an apsidal precession of planetary orbit.^[5]