How the ‘hell planet’ covered in lava oceans got so close to its star

By Georgina Torbet December 11, 2022

Of the over 5,000 known planets outside our solar system, one of the most dramatic is 55 Cancri e. Affectionately known as the “hell planet,” it orbits so close to its star that it reaches temperatures of 3,600 degrees Fahrenheit and its surface is thought to be to 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 a year there lasts less than a day here on Earth. “While the 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 Yale University in a statement.

An artist’s impression of the planet Janssen (orange circle), which orbits its star so closely that its entire surface is a lava ocean that reaches temperatures of around 2,000 degrees Celsius. — An artist’s impression of the planet Janssen (orange circle), which orbits its star so closely that its entire surface is a lava ocean that reaches temperatures of around 2,000 degrees Celsius. Lucy Reading-Ikkanda/Simons Foundation

Researchers used a tool called the EXtreme PREcision Spectrometer (EXPRES) at the Lowell Observatory’s Lowell Discovery Telescope in Arizona to look at the light coming from the host star and focused on the way that light changed when the planet moved between the star and Earth. This told them that the planet orbits around the equator of the star, 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 at different degrees respective to the orbital plane.

Recommended Videos

This is unlike our solar system, where all of the planets essentially sit in 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 in close to the star. That’s how it ended up so hot. “Astronomers expect that this planet formed much farther away and then spiraled into its current orbit,” Fischer said. “That journey could have kicked the planet out of the equatorial plane of the star, but this result shows the planet held on tight.”

The research is published in the journal Nature Astronomy.

Topics

Tech News

Georgina Torbet

Space Writer

Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…

Space

Long-lost moon could explain how Saturn got its rings

Artistic rendering of the moon Chrysalis disintegrating in Saturn’s intense gravity field. The chunks of icy rock eventually collided and shattered into smaller pieces that became distributed in the thin ring we see today.

Saturn is famed for its beautiful rings, but these rings are something of a puzzle to astronomers. Originally, it was thought that they must have formed around the same time as the planet, over 4 billion years ago. But data from the Cassini spacecraft suggested the rings might be much younger than that, forming less than 100 million years ago. Now, a new study suggests that the rings could have been formed from a long-lost moon, explaining several of Saturn's peculiarities.

Saturn rotates with a tilt of 27 degrees, slightly off the plane at which it orbits the sun, and its rings are tilted too. Recently published research proposes that both of these factors can be explained by a former moon, named Chrysalis, which came close to the planet and was torn apart. Most of the moon was absorbed by the planet, but the rest of it created the stunning rings.

Space

Researchers discover planet in the habitable zone of an ultra-cool star

The telescopes of the SPECULOOS Southern Observatory gaze out into the stunning night sky over the Atacama Desert, Chile.

Even though we've discovered over 5,000 exoplanets, or planets outside of our solar system, most of these aren't very Earth-like. They're often much bigger than Earth, being more like gas giants Saturn and Jupiter than small and rocky, and relatively few are located in the habitable zone where liquid water could exist on their surface. That's why it's exciting when a planet comparable to Earth is discovered in its habitable zone -- as one such recently discovered planet is.

Researchers looked at a planet called LP 890-9b or TOI-4306b, previously discovered by NASA's Transiting Exoplanet Survey Satellite. Using a ground-based telescope called SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars), they studied the planet which is around 30% larger than Earth and orbits extremely close to its star, with a year lasting just 2.7 days.

Space

Intriguing exoplanet could be entirely covered in ocean

Artistic rendition of the exoplanet TOI-1452 b, a small planet that may be entirely covered in a deep ocean.

Astronomers have discovered an intriguing exoplanet that could be entirely covered in water. The potential ocean world is called TOI-1452 b, located around 100 light-years away in the constellation of Draco.

The planet was discovered by an international team using data from NASA's Transiting Exoplanet Survey Satellite, or TESS, and is a type of planet called a super-Earth which is somewhat larger and heavier than Earth. It is in its host star's habitable zone, meaning it is the right distance from the star for liquid water to exist on its surface.