Confirmed exoplanet · Database record + computed analysis
HAT-P-20 b
A confirmed world orbiting HAT-P-20, 231.7 light-years away.
A gas giant
9.72 Earth radii, Jupiter-class (Jupiter is 11.2). With 2302.9 Earth masses packed into that size, its density points to rock and iron rather than gas. Orbiting this close, it is a classic 'hot Jupiter', a giant that migrated inward from where it formed.
The orbit
Its year, one full orbit, takes just 2.9 Earth days. Orbiting this tightly around a cool star, it is very likely tidally locked: one hemisphere in permanent day, the other in permanent night.
Temperature and starlight
Its equilibrium temperature (the airless-world estimate) is about 697 °C. Hotter than Venus's surface. It receives 85.1 times the starlight Earth gets.
Its sun
Its star is an orange K-type (4,595 K), K3: cooler and longer-lived than the Sun, a class some astronomers consider ideal for habitability.
How far is that, really?
At 232 light-years, tonight's light from this system left it around the year 1794. A Voyager-speed probe would need roughly 4,099,250 years to get there.
How we found it
It was found by the transit method: the planet crosses its star's face on schedule, dimming it by a tiny, repeating fraction. The dip's depth gives the planet's size. The discovery was announced in 2010 from HATNet.
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.