WASP-121

system

WASP-121 is a hot F-type star about 880 light-years away in Puppis, orbited by one of the most extreme worlds known: WASP-121 b, an ultra-hot Jupiter so scorched (over 2,400 K) that heavy metals glow in its air and stream away into space.

Open in 3D viewSee WASP-121 in the live, interactive 3D map

Key facts

Type

Hot F star + ultra-hot Jupiter

Distance

880 light-years

Confirmed planets

Dayside

> 2,400 K — metals escaping

Science

Classification

Type: Single hot F-type system
Central star: WASP-121 — F6V, ~6628 K, 1.33 M☉

Planets

Confirmed planets: 1 · WASP-121 b, an ultra-hot Jupiter
Extremes measured: Glowing water, escaping iron & magnesium

Distance

Distance: 880 light-years · in Puppis, the Stern

How we know

Note: One confirmed transiting planet with a measured mass (NASA Exoplanet Archive, checked 2026-07-07), so its size and density are real. The glowing water, hot stratosphere and escaping iron/magnesium are genuine spectroscopic detections — but the planet's air has never been imaged. Placed at its real position, 880 light-years away.

Discovery & history

Name: A designation from the Wide Angle Search for Planets (WASP) survey; the star has no proper name.

WASP-121 b was found transiting in 2015 by the WASP survey. Because it is so hot and puffed-up, telescopes have read its atmosphere in extraordinary detail — finding glowing water, a scorching stratosphere, and iron and magnesium escaping the planet's grip, one of the clearest cases of a world evaporating under its star.

Images

NASA/JPL computer-simulation views of the ultra-hot Jupiter WASP-121 b, whose atmosphere is glowing and escaping — a simulation, not a photograph. — NASA/JPL-Caltech/Aix-Marseille University/V. Parmentier · Wikimedia Commons

Images from open archives · credit shown per image