K2-18
Star
K2-18 — a cool red dwarf about a third of the Sun's mass, 124 light-years away in Leo. Faint and long-lived, it is the kind of star most planets orbit — and its habitable-zone sub-Neptune has made it one of the most-studied stars in the sky.
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Key facts
Mass
7.14 × 10²⁹ kg
0.359 M☉
Radius
285,933 km
41% of the Sun's radius
Surface temperature
3,457 K (3,184 °C)
Luminosity
8.31 × 10²⁴ W
Spectral type
M2.5V (red dwarf)
Science
Physical
- Mass
- 7.14 × 10²⁹ kg · 0.359 M☉
- Radius
- 285,933 km · 41% of the Sun's radius
- Density
- 7,292 kg/m³ · 7.3× water
- Computed from mass and radius
- Spectral type
- M2.5V (red dwarf)
Motion through space
- Proper motion
- 0.155 arcseconds per year · its drift across our sky
- SIMBAD — 2020yCat.1350....0G
- Speed across our line of sight
- 28.1 km/s
- Computed from proper motion and parallax
Rotation
- Note
- A relatively quiet red dwarf, aiding the delicate atmospheric measurements of its planet.
Composition
- By mass
- A hydrogen/helium red dwarf about a third of the Sun's mass and ~2% of its light. Cool and long-lived, it is the commonest kind of star in the Galaxy — and its temperate sub-Neptune has made it one of the most-scrutinised.
Temperature
- Surface
- 3,457 K (3,184 °C)
Radiation & temperature
- Luminosity
- 8.32 × 10²⁴ W · 0.0217 L☉
- Surface temperature
- 3,457 K (3,184 °C)
- Peak wavelength
- 838 nm · near-infrared (mostly invisible to the eye)
- Computed (Wien's law) from the surface temperature
Discovery & history
- Method
- Telescope
- Name
- A K2-mission catalogue designation; no proper name.
Catalogued by the K2 mission in 2015, when a planet was seen transiting it; the star has since been a prime JWST target because its planet sits in the temperate zone.
Images
Images from open archives · credit shown per image