New research shows that the exoplanet Janssen orbits very close to its host star, causing its surface temperature to reach levels that can melt everything.
First discovered in 2004, Janssen is also known by several other names such as 55 Cancri e or 5 Cnc e, but it is most famously referred to as the “hellish planet”. This is due to its molten lava ocean on the surface, with temperatures nearing 2,000°C.
Simulation of the planet Janssen orbiting the Copernicus star. (Image: NASA)
This rocky body, located 40 light-years away, is classified as a super-Earth. It has a diameter twice that of Earth and is approximately 8.6 times heavier. Beneath its molten lava ocean, there may be diamonds.
Janssen orbits the Copernicus star in a very tight orbit. Astronomers have long wondered whether it has always been so close to its host star.
In a new study published in the journal Nature Astronomy on December 8, a team of astronomers from Yale University, led by Professor Debra Fischer, used a new tool called EXPRES, or the EXtreme PREcision Spectrograph, to determine the precise nature of the planet’s orbit.
Installed on the Lowell Discovery Telescope at the Lowell Observatory in Flagstaff, Arizona, USA, EXPRES can measure tiny shifts in the starlight from Copernicus as Janssen moves between Earth and the star, similar to how the Moon obscures the Sun during a solar eclipse.
The research team determined that Janssen orbits along the equator of Copernicus at such a close distance that it takes only 17.5 hours to complete one orbit around the star. However, Janssen is not the only planet orbiting Copernicus; this system also contains four other planets on different orbits.
Astronomers believe that Janssen originally resided in a much farther and cooler orbit before drifting closer to Copernicus. Subsequently, the gravitational pull from the star’s equator altered the planet’s orbit and locked it in place.
Despite the fact that Janssen is not always near the host star, the research team concluded that this exoplanet is always scorching hot. As it approaches Copernicus, the hellish planet becomes even hotter.
“It can get hot enough that nothing we know could exist on its surface,” emphasized lead author Lily Zhao, a researcher at the Flatiron Institute’s Center for Astrophysics in New York.
Our solar system is flat like a pancake, with all planets orbiting the Sun in a single plane because they formed from the same gas and dust disk. However, as astronomers study other planetary systems, they discover that many of them do not contain planets orbiting in a flat plane, raising questions about how unique our solar system is in the universe.
The new discovery about the super-Earth Janssen and the Copernicus system will help scientists better understand the formation of planetary systems and how planets develop orbits around their central star.
