Distant 'hell planet' with diamond core is the victim of a gravitational catastrophe

An artist’s drawing of Janssen. The planet orbits its star so closely that its surface is a 3632 degree Fahrenheit (2000 degrees celcius) lava ocean.
An artist’s drawing of Janssen. The planet orbits its star so closely that its surface is a 3632 degree Fahrenheit (2000 degrees Celsius) lava ocean. (Image credit: ESA/Hubble, M. Kornmesser)

Scientists studying a distant "hell planet" where clouds rain lava, the oceans are molten and the core is filled with diamonds have found that the nightmarish planet wasn’t always so bad; but it became infernally hot after being yanked closer to its sun.

The planet, classified as 55 Cancri e, is nicknamed "Janssen" after Zacharias Janssen, a Dutch spectacle-maker who is dubiously attributed with the invention of the first optical telescope. The a rocky world, 40 light-years away from us, orbits its star Copernicus 70 times closer than Earth orbits the sun — meaning one of its years lasts just 18 hours.

But Janssen may not have always been this way, a new orbital analysis published Dec. 8 in the journal Nature Astronomy (opens in new tab) revealed. The planet orbits Copernicus, itself part of a binary pair with a red dwarf star, alongside four other planets; and while it was always hot, the planet may have only gained its hellish conditions after being reeled in toward its star's equator following shifts in the gravity felt from Copernicus, the red dwarf and Janssen's sister planets. 

Related: Giant blobs in Earth's mantle may be driving a 'diamond factory' near our planet's core

"We've learned about how this multi-planet system — one of the systems with the most planets that we've found — got into its current state," study lead author Lily Zhao, a research fellow at the Flatiron Institute's Center for Computational Astrophysics (CCA) in New York City, said in a statement

The researchers wanted to study the distant system to assess how its planets evolved and how it is different from our flat, pancake-like solar system where all planets occupy mostly identical orbital planes. Understanding these differences will help scientists to assess the likelihood of life existing on Earth-like worlds elsewhere in the universe.

To study the distant system, the researchers used the Lowell Discovery Telescope in Arizona to measure miniscule shifts in light levels as the hell planet moved between Copernicus and Earth. Copernicus is also spinning, so the scientists used the telescope's Extreme Precision Spectrometer (EXPRES) to measure the tiny doppler shifting of the star's light and spot which part of the star was being blocked by the planet at any given moment. (The Doppler effect causes light from a source travelling towards the oberver to be bluer, and light from a source traveling away redder — so the star’s light appears bluer on one half where the star is moving towards the viewer, and redder on its other half where it is moving away.)

This enabled the scientists to reconstruct the planet's unusually close orbit around Copernicus' equator, which they think it entered into after the gravitational misalignments in the system pulled it closer to the star. Copernicus' spin bulges out the star’s midsection and flattens its top and bottom, which led Janssen to be tugged into line along the equator of the star. This is an especially strange orbit compared with the other planets in the system, whose orbits don't even cross between Copernicus and Earth.

The astrophysicists say they want to expand their study to search for planets like our own and learn how they evolved.

"We're hoping to find planetary systems similar to ours," Zhao said. "And to better understand the systems that we do know about."

Ben Turner
Staff Writer

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.