---
title: "The K2-398 system"
url: "https://spacecatalog.org/system/k2-398"
release: "DR1"
licence: "No licence stated; acknowledgement requested"
citation: "This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value."
---

# The K2-398 system

K2-398 is a G2 yellow star in Sextans, 1980 ly away, with 2 known planets. All of them were detected by transit.

## The planets, innermost first

| Planet | Orbit (AU) | Period | Radius | Mass | Equilibrium T |
| --- | --- | --- | --- | --- | --- |
| [b](https://spacecatalog.org/object/k2-398-b) | — | 6.393 d | 2.27 R⊕ | 5.79 M⊕ | — |
| [c](https://spacecatalog.org/object/k2-398-c) | — | 18.79 d | 5.10 R⊕ | 22.8 M⊕ | — |

2 with no published orbit, sorted last.

Every figure is the planet's composite parameter from the [NASA Exoplanet Archive (Planetary Systems Composite Parameters)](https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars), one consistent set per world. Semi-major axes are orbits about the star, not distances from Earth.

This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value.

## The host star

| Quantity | Value |
| --- | --- |
| CLASS | G2 yellow star |
| SPECTRAL TYPE | G2 |
| MASS | 0.945 M☉ |
| RADIUS | 1.239 R☉ |
| SURFACE TEMPERATURE | 5946 K |
| LUMINOSITY | 1.73 L☉ |
| DISTANCE FROM EARTH | 1980 ly |
| APPARENT MAGNITUDE | 13.29 |
| CONSTELLATION | Sextans |
| STARS IN SYSTEM | 1 |

The star itself: https://spacecatalog.org/object/k2-398

The page itself, with the orbits drawn: https://spacecatalog.org/system/k2-398