Confirmed exoplanet · Database record + computed analysis
HD 99109 b
A confirmed world orbiting HD 99109, 178.7 light-years away.
A gas giant
14.30 Earth radii, Jupiter-class (Jupiter is 11.2). At only 139.8 Earth masses for that size, it must be substantially gas or volatile ices: puffy, not rocky.
The orbit
Its year takes 439 Earth days (1.2 Earth years).
Temperature and starlight
Its equilibrium temperature (the airless-world estimate) is about -34 °C. In the range where, with the right atmosphere, liquid water is conceivable; a real atmosphere could shift the true surface figure a lot (Earth's equilibrium value is −18 °C, yet we average +15 °C). It receives 0.55 times Earth's starlight, the same order as our own world.
Its sun
Its star is an orange K-type (5,282 K), G8/K0 IV: cooler and longer-lived than the Sun, a class some astronomers consider ideal for habitability.
How far is that, really?
At 179 light-years, tonight's light from this system left it around the year 1847. A Voyager-speed probe would need roughly 3,161,691 years to get there.
How we found it
It was found by the radial-velocity method: the planet's gravity swings its star in a small circle, and that wobble shows up as a rhythmic Doppler shift in the starlight. The wobble's size gives the planet's minimum mass. The discovery was announced in 2005 from W. M. Keck Observatory.
Everything above is computed from the archive’s measured values for this planet. Where a quantity is missing, the statement is omitted rather than guessed.
About this record
The measured values come from the NASA Exoplanet Archive, and any missing value has not been determined yet; the Atlas never fills gaps with guesses. More standout worlds: Proxima b, TRAPPIST-1e, K2-18 b, 55 Cancri e, and the detection methods that found them all.