13point8All planet systems
2 known planets · 1,980 light years

K2-398

K2-398 is a yellow star (G2) 1,980 light years away, with 2 confirmed planets. Distances and orbital speeds are to scale; the star and planets are enlarged so you can see them.

Day 0
habitable zone (estimate)planet orbits

Green band: where liquid water could exist on a planet's surface. Drag to turn the system, pinch or scroll to zoom.

The star

The star

K2-398

Type
G2
Surface
≈ 5,946 K
Size
1.24 × the Sun
Mass
0.94 × the Sun
Brightness
1.82 × the Sun
Habitable zone
1–2.35 AU

The planets

K2-398

K2-398 b

Year
6.39 days
Distance from star
0.0662 AU
Mass
5.8 Earths
Size
2.3 × Earth
Found
2022, transit (K2)
Outside the habitable zone
K2-398

K2-398 c

Year
18.79 days
Distance from star
0.136 AU
Mass
23 Earths
Size
5.1 × Earth
Found
2022, transit (K2)
Outside the habitable zone

Masses found by the wobble method are minimums, because the orbit's tilt is unknown. Temperatures are equilibrium estimates for a bare planet, before any atmosphere.

How we know

The shadow

The planet passes in front of its star and dims it by a fraction of a percent, every orbit. The dip gives the planet's size and year.

Sources

  1. Planet and star parameters: NASA Exoplanet Archive, Planetary Systems Composite Parameters, retrieved 1 Nov 2026. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program.
  2. Position: HYG Database v4.1 (CC BY-SA 4.0).
  3. Habitable zone: a simple estimate from the star's brightness (√L × 0.95 to 1.67 AU), shown as a guide.
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