55 Cancri e – an Exoplanet

55 Cancri e – an Exoplanet

55 Cancri e is an exoplanet orbiting the Sun-like host star 55 Cancri A. It’s also known as Janssen, and it’s only 41 light-years distant from the star Copernicus. The exoplanet’s mass is around 8.63 Earth masses, and its diameter is almost twice that of the Earth, making it the first super-Earth identified around a main sequence star, predating Gliese 876 d by a year. It takes fewer than 18 hours to complete an orbit and is the planet with the fewest known planets in its solar system.

On August 30, 2004, 55 Cancri e was discovered. However, prior to the 2010 observations and recalculations, this planet was expected to orbit the star in around 2.8 days. Because of its molten surface, the planet is inhospitable. However, because of the silicates in the atmosphere, the skies on this planet are always dazzling. It was announced in October 2012 that 55 Cancri e could be a carbon planet.

In February 2016, NASA’s Hubble Space Telescope stated that it had identified hydrogen and helium (as well as hints of hydrogen cyanide), but no water vapor, in the atmosphere of 55 Cancri e, the first time the atmosphere of a super-Earth exoplanet has been effectively examined.


55 Cancri e is a super-Earth exoplanet orbiting a G-type star like our Sun. It has a mass of 8.08 Earths, takes 0.7 days to complete one orbit around its star, and is 0.01544 AU away from it.

55 Cancri e, like the vast majority of known extrasolar planets, was discovered by detecting fluctuations in its star’s radial velocity. This was accomplished by the use of sensitive measurements of the Doppler shift of the spectrum of 55 Cancri A. Three more planets were known to circle the star at the time of its discovery. After accounting for these planets, there was a signal at roughly 2.8 days that may be explained by a planet of at least 14.2 Earth masses in a very near orbit. The same measurements were used to confirm the existence of the uncertain planet 55 Cancri c.

Orbit and mass

The radial velocity approach used to find 55 Cancri e yields a minimum mass of 7.8 times that of Earth, or 48% of Neptune’s mass. The transit reveals that its inclination is approximately 83.4 ± 1.7, implying that the true mass is near to the minimum. 55 Cancri e and b are also coplanar.

The planet is very likely tidally locked, which means it has a constant day side and a perpetual night side.


Gliese 436 b is exposed to more radiation than 55 Cancri e. Temperatures on the planet’s star-facing side exceed 2,000 kelvin (about 1,700 degrees Celsius or 3,100 degrees Fahrenheit), making iron melt. Spitzer Space Telescope infrared scanning revealed an average front-side temperature of 2,573 K (2,300 °C; 4,172 °F) and a back-side temperature of around 1,644 K (1,371 °C; 2,500 °F).

It wasn’t clear whether 55 Cancri e was a small gas giant like Neptune or a huge rocky terrestrial planet at first. In 2011, astronomers were able to quantify the planet’s density after confirming a transit of the planet. It was thought to be a water planet at first.

Another option is that 55 Cancri e is a solid planet made of carbon-rich material rather than the oxygen-rich stuff that makes up the Solar System’s terrestrial planets. In this hypothesis, carbon would account for around one-third of the planet’s mass, with much of it forming diamond as a result of the planet’s core temperatures and pressures. More observations are required to confirm the planet’s nature.