NASA (Exoplanet Catalog artwork)51 Pegasi b
also named DimidiumThe 1995 discovery that proved planets orbit other Sun-like stars
Overview
51 Pegasi b, officially named Dimidium, is an extrasolar planet approximately 50 light-years away in the constellation Pegasus. Dimidium was the first exoplanet to be discovered orbiting a main-sequence star, the Sun-like 51 Pegasi — a major astronomical discovery. It is the prototype for a class of planets called hot Jupiters.
Source: Wikipedia
NASA: 51 Pegasi b is a gas giant exoplanet that orbits a G-type star. Its mass is 0.61 Jupiters, it takes 4.2 days to complete one orbit of its star, and is 0.052 AU from its star. Its discovery was announced in 1995.
Why it matters
- Found by Michel Mayor and Didier Queloz, who shared the 2019 Nobel Prize in Physics for it.
- A 'hot Jupiter' hugging its star every 4.2 days — a type of planet nobody expected to exist.
- Its surprising orbit forced theorists to invent planetary migration.
NASA puts it this way: “51 Pegasi b is a gas giant exoplanet that orbits a G-type star. Its mass is 0.46 Jupiters, it takes 4.2 days to complete one orbit of its star, and is 0.0527 AU from its star. Its discovery was announced in 1995.”
Discovery & system
- Discovered
- 1995 · Radial Velocity · Haute-Provence Observatory
- Discovery paper
- Mayor & Queloz 1995
- Discoverers
- Michel Mayor, Didier Queloz
- Host star
- 51 Peg · G5V · 5,761 K · 1.07 M☉
- System
- 1 known planet
The system
| World | Period | Distance | Radius | Mass | Temp. |
|---|---|---|---|---|---|
| 51 Peg b | 4.23 d | 0.052 AU | 1.26 R♃ | 0.61 M♃ | 1,329 K |
By the numbers
- Radius
- 1.26 R♃14.1 R⊕
- Mass
- 0.61 M♃194 M⊕
- Orbital period
- 4.23 d0.01 yr
- Distance from star
- 0.052 AU7.78 million km
- Eccentricity
- 0.006nearly circular
- Equilibrium temp.
- 1,329 K1,056 °C
- Starlight received
- 506 × Earth
- Distance from Earth
- 50.4 ly15.5 pc
- Density
- 0.38 g/cm³0.07 × Earth
Sources
Image: NASA (Exoplanet Catalog artwork) · NASA media: generally free of copyright · image page
Text: Wikipedia (CC BY-SA 4.0). Taglines and highlights are editorial.