Of the more than 5,000 known planets outside our solar system, one of the most dramatic is 55 Cancri e. Affectionately known as the “planet from hell,” it orbits so close to its star that it reaches temperatures of 3,600 degrees Fahrenheit and its surface is believed to be covered in an ocean of lava. Located 40 light-years away, the planet has been a source of fascination for its extreme conditions, and recently researchers shared a new theory for how it got so hot.
The planet orbits its star, 55 Cancri A, at a distance of 1.5 million miles, which means that a year there lasts less than a day here on Earth. “While Earth completes one orbit around our sun in 365 days, the planet studied here orbits once every 17.5 hours, hugging its host star, 55 Cnc,” said study author Debra Fischer of the University of Yale in a release.
The researchers used a tool called the EXtreme PREcision Spectrometer (EXPRES) on the Lowell Discovery Telescope at Lowell Observatory in Arizona to observe the light coming from the host star and zeroed in on the way the light changed as the planet moved between the star. and earth. This told them that the planet orbits the star’s equator, which is different from other planets in the system. There are five exoplanets in the system, with a pair of stars at the center, and the planets orbit in different degrees relative to the orbital plane.
This is unlike our solar system, where all the planets essentially sit on the same flat plane. In our case, this is probably because all the planets formed from the same disk of dust and gas. So the fact that they are different orbits seen in the 55 Cancri systems suggests that these planets could have formed in different ways.
The planet 55 Cancri e is thought to have formed in a cooler orbit before being pulled close to the star. That’s how it ended up so hot. “Astronomers expect this planet to have formed much farther out and then spiraled into its current orbit,” Fischer said. “That trip could have ejected the planet from the star’s equatorial plane, but this result shows that the planet held on tight.”
The research is published in the journal nature astronomy.