---
title: "The HD 191939 system"
url: "https://spacecatalog.org/system/hd-191939"
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 HD 191939 system

HD 191939 is a G0 yellow star in Draco, 188.1 ly away, with 6 known planets. Their orbits run from 0.0804 to 3.71 AU.

## The planets, innermost first

| Planet | Orbit (AU) | Period | Radius | Mass | Equilibrium T |
| --- | --- | --- | --- | --- | --- |
| [b](https://spacecatalog.org/object/hd-191939-b) | 0.0804 | 8.88 d | 3.41 R⊕ | 10 M⊕ | 880 K |
| [c](https://spacecatalog.org/object/hd-191939-c) | 0.175 | 28.58 d | 3.19 R⊕ | 8 M⊕ | 600 K |
| [d](https://spacecatalog.org/object/hd-191939-d) | 0.213 | 38.35 d | 3.00 R⊕ | 2.8 M⊕ | 540 K |
| [e](https://spacecatalog.org/object/hd-191939-e) | 0.407 | 101.1 d | 13.00 R⊕ | 112 M⊕ | 390 K |
| [g](https://spacecatalog.org/object/hd-191939-g) | 0.812 | 284 d | 3.74 R⊕ | 13.5 M⊕ | 278 K |
| [f](https://spacecatalog.org/object/hd-191939-f) | 3.71 | 7.934 yr | 13.20 R⊕ | 915 M⊕ | 125 K |

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 | G0 yellow star |
| SPECTRAL TYPE | G0 |
| MASS | 0.853 M☉ |
| RADIUS | 0.947 R☉ |
| SURFACE TEMPERATURE | 5365 K |
| LUMINOSITY | 0.748 L☉ |
| DISTANCE FROM EARTH | 188.1 ly |
| APPARENT MAGNITUDE | 8.97 |
| CONSTELLATION | Draco |

The star itself: https://spacecatalog.org/object/hd-191939

The page itself, with the orbits drawn: https://spacecatalog.org/system/hd-191939