Secrets of the cold giant 51 Eridani b revealed through high-resolution spectroscopy

Star system: 51 Eridani | Distance from the Sun: 97.1 light years

Using the advanced HiRISE instrument at the Very Large Telescope, astronomers have performed a detailed analysis of 51 Eridani b, one of the faintest directly imaged planets ever found. 

By measuring the planet's radial velocity across four different time periods, the team successfully mapped its full 3D orbit, breaking previous uncertainties. They discovered that the planet follows a highly stretched, or eccentric, path rather than a circular one. This 'oval' orbit suggests that the system had a chaotic past, likely influenced by the gravitational pull of an undiscovered outer planet that pushed 51 Eridani b into its current trajectory.

Scientific study

Cold and eccentric: a high-spectral resolution view of 51 Eri b with VLT/HiRISE (external link)