Confirmed exoplanet · Database record + computed analysis
KMT-2021-BLG-0171L b
A confirmed world orbiting KMT-2021-BLG-0171L, 15,003.2 light-years away.
A sub-Neptune
3.35 Earth radii, likely a rocky core under a thick gas or steam envelope rather than a walkable surface. At only 11.2 Earth masses for that size, it must be substantially gas or volatile ices: puffy, not rocky.
Its sun
Its star is an orange K-type (5,200 K): cooler and longer-lived than the Sun, a class some astronomers consider ideal for habitability.
How far is that, really?
At 15,003 light-years, tonight's light from this system left it around the year -12977. A Voyager-speed probe would need roughly 265,445,382 years to get there.
How we found it
It was found by gravitational microlensing: the star (and planet) drifted in front of a farther star, and their gravity briefly magnified the background light in a telltale pattern. Such alignments never repeat, so each detection is a one-time event. The discovery was announced in 2022 from KMTNet.
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.