The HD 191939 System

6 planets 1 in habitable zone Draco

HD 191939 is a planetary system in the constellation Draco hosting 6 confirmed exoplanets, about 175 light-years from Earth. One of its planets orbits within the habitable zone, where liquid water could exist on a planetary surface.

Size Comparison: The Planets of HD 191939

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Planets without a measured radius are not shown.

HD 191939: Star and Habitable Zone

HD 191939

Spectral type: G9 V
Surface temperature: 5,348 K (Sun: 5,772 K)
Mass: 0.81 M☉
Radius: 0.94 R☉
Luminosity: 0.6500 L☉
Age: 8.7 billion years (Sun: 4.6)

HD 191939 b HD 191939 c HD 191939 d HD 191939 e HD 191939 f → HD 191939 g

Too hot Optimistic habitable zone Conservative habitable zone Too cold

Habitable zone of HD 191939: 0.620–1.481 AU (conservative: 0.786–1.404 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.

See the full interactive habitable-zone view in the Exoplanet Explorer app ›

All 6 Planets in the HD 191939 System

Planet	Type	Orbit	Radius	ESI	Discovered
HD 191939 b	Puffy Planet	8.9 d	3.41 R⊕	0.21	2020
HD 191939 c	Puffy Planet	29 d	3.20 R⊕	0.26	2020
HD 191939 d	Puffy Planet	38 d	3.00 R⊕	0.29	2020
HD 191939 e	Cold Gas Giant	101 d	—	0.26	2022
HD 191939 f	Cold Gas Giant	2,898 d	—	0.13	2022
HD 191939 g HZ	Neptune-like	284 d	—	0.59	2022

Discovery History

The first planet found here, HD 191939 b, was discovered in 2020 using the transit method. The most recent addition, HD 191939 g, followed in 2022.

2020 — HD 191939 b (Transit)
2020 — HD 191939 c (Transit)
2020 — HD 191939 d (Transit)
2022 — HD 191939 e (Radial Velocity)
2022 — HD 191939 f (Radial Velocity)
2022 — HD 191939 g (Radial Velocity)

Frequently Asked Questions About HD 191939

How many planets does HD 191939 have?

HD 191939 has 6 confirmed exoplanets. More may await discovery.

Are any planets in the HD 191939 system habitable?

One planet in the system orbits within the habitable zone, where liquid water could exist. Actual habitability depends on atmospheres and composition, which are not yet known.

How far away is HD 191939?

HD 191939 is about 175 light-years from Earth in the constellation Draco.

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