NASA (Exoplanet Catalog artwork)55 Cancri e
also named JanssenThe 'diamond planet' with a magma ocean and a JWST-detected atmosphere
Overview
55 Cancri Ae, officially named Janssen, is an exoplanet orbiting a Sun-like host star, 55 Cancri A. The mass of the exoplanet is about eight Earth masses and its diameter is about twice that of the Earth. 55 Cancri Ae was discovered in data taken during 2003–2004 and announced in 2004, thus making it the first super-Earth discovered around a main sequence star, predating Gliese 876 d by a year. It is the innermost planet in its planetary system, taking less than 18 hours to complete an orbit. However, until the 2010 observations and recalculations, this planet had been thought to take about 2.8 days to orbit the star.
Source: Wikipedia
NASA: 55 Cancri e is a super Earth exoplanet that orbits a K-type star. Its mass is 7.99 Earths, it takes 0.7 days to complete one orbit of its star, and is 0.01544 AU from its star. Its discovery was announced in 2004.
Why it matters
- Eight Earth masses on a 17.7-hour orbit around a naked-eye star 41 light-years away.
- A 2012 carbon-rich interior model earned it the 'diamond planet' nickname, since tempered.
- In 2024 JWST found a thick atmosphere of carbon monoxide or dioxide, probably outgassed from the magma ocean.
NASA puts it this way: “This super hot world is covered in a global ocean of lava and has sparkling skies.”
Discovery & system
- Discovered
- 2004 · Radial Velocity · McDonald Observatory
- Discovery paper
- McArthur et al. 2004
- Host star
- 55 Cnc · G8 V · 5,172 K · 0.91 M☉
- System
- 7 known planets, 2 stars
- Siblings
- 55 Cnc b, 55 Cnc c, 55 Cnc f, 55 Cnc d
The system
| World | Period | Distance | Radius | Mass | Temp. |
|---|---|---|---|---|---|
| 55 Cnc e | 17.7 h | 0.015 AU | 1.88 R⊕ | 7.99 M⊕ | 1,958 K |
| 55 Cnc b | 14.7 d | 0.118 AU | 1.24 R♃ | 0.83 M♃ | 700 K |
| 55 Cnc c | 44.4 d | 0.247 AU | 0.76 R♃ | 54.47 M⊕ | 499 K |
| 55 Cnc f | 260.6 d | 0.802 AU | 0.68 R♃ | 44.81 M⊕ | 277 K |
| 55 Cnc d | 13.1 yr | 5.6 AU | 1.16 R♃ | 3.88 M♃ | 105 K |
By the numbers
- Radius
- 1.88 R⊕11,946 km
- Mass
- 7.99 M⊕47.72 ×10²⁴ kg
- Orbital period
- 17.7 h
- Distance from star
- 0.015 AU2.31 million km
- Eccentricity
- 0.05elliptical
- Equilibrium temp.
- 1,958 K1,685 °C
- Starlight received
- 2,658 × Earth
- Distance from Earth
- 41.1 ly12.6 pc
- Density
- 6.66 g/cm³1.21 × 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.