Exoplanet · mini-Neptune
HD 191939 d
HD 191939 d is a mini-Neptune orbiting the star HD 191939. Its year lasts 38.4 Earth days. It was discovered in 2020 by the Transit method.
| Host star | HD 191939 |
|---|---|
| Distance | 174.9 light-years (53.6 pc) |
| Orbital period | 38.4 days |
| Orbital radius | 0.213 AU |
| Eccentricity | 0.031 |
| Radius | 3 R⊕ · 0.267 R♃ |
| Mass | 2.8 M⊕ · 0.00881 M♃ |
| Density | 0.57 g/cm³ |
| Surface gravity | 0.312 × Earth |
| Equilibrium temperature | 540 K (267 °C) |
| Stellar flux received | 14.3 × Earth |
| Discovery method | Transit |
| Discovery year | 2020 |
| Discovered by | Transiting Exoplanet Survey Satellite (TESS) |
Habitable zone
Inside the inner edge of the habitable zone: it receives 14.3 times the light the Earth does, too hot to keep liquid water on its surface.
Its star in the sky
In the planet's sky its star is a disc 2.3° across: 4.4 times the Sun as we see it from Earth.
In the sky
Too faint for the naked eye (magnitude 8.97); binoculars will find it. Visible from the whole Northern Hemisphere and south to latitude 23° S. North of latitude 23° N it never sets. It stands highest at midnight in July, the best time to observe it.
Light's journey
The light you see tonight set out around the year 1851. At the speed of Voyager 1, the fastest craft leaving the Solar System (16.9 km per second), the trip would take 3.1 million years.
Planets in the same system
- HD 191939 b 8.88-day orbit · 3.41 R⊕
- HD 191939 c 28.6-day orbit · 3.2 R⊕
- HD 191939 e 101-day orbit · 13 R⊕
- HD 191939 g 284-day orbit · 3.74 R⊕
- HD 191939 f 2,900-day orbit · 13.2 R⊕
Data: NASA Exoplanet Archive, PSCompPars. Its look in the simulation is a rendering based on the measured radius, mass and temperature.