Skip to main content
  1. Home
  2. Space
  3. News

Rocky exoplanets are more like Earth inside than we thought

By
This artist’s rendering shows a white dwarf star with two planets. Mark Garlick

When looking for exoplanets that are similar to Earth, astronomers typically look for worlds in orbit around a type of star called a red dwarf on an M-dwarf. These types of star are somewhat similar to our sun and are common in our galaxy, making up about 70% of stars here. However, new research shows that rocky exoplanets in orbit around a different type of star, a white dwarf, can have interiors that are surprisingly similar to our planet.

White dwarfs are shrunken remains of once-bright stars that have extremely strong gravity. Typically, this gravity means the surface of the stars is composed of light elements like hydrogen and helium, but in some cases, you find “polluted” white dwarfs that have heavier elements like magnesium, iron, and oxygen in their atmospheres. These elements are introduced to the white dwarf when a rocky exoplanet crashes into the star, which gives astronomers evidence of what the exoplanets were like before they were destroyed.

Recommended Videos

“By observing white dwarfs and the elements present in their atmosphere, we are observing the elements that are in the body that orbited the white dwarf,” Alexandra Doyle, a graduate student in the Department of Earth, Planetary, and Space Sciences at the University of California, Los Angeles, explained in a statement. “The white dwarf’s large gravitational pull shreds the asteroid or planet fragment that is orbiting it, and the material falls onto the white dwarf.”

Related

Doyle and her colleagues looked at white dwarfs to see what kind of elements had been present in the planets that used to orbit them. “If I were to just look at a white dwarf star, I would expect to see hydrogen and helium,” Doyle said. “But in these data, I also see other materials, such as silicon, magnesium, carbon, and oxygen — material that accreted onto the white dwarfs from bodies that were orbiting them.”

The surprising finding here was how alike the exoplanets were to Earth beneath their rocky exteriors. “How similar are the rocks the researchers analyzed to rocks from the Earth and Mars? Very similar,” Doyle said. “They are Earth-like and Mars-like in terms of their oxidized iron. We’re finding that rocks are rocks everywhere, with very similar geophysics and geochemistry.”

The research is published in the journal Science.

Editors' Recommendations

Topics
Georgina Torbet
Georgina Torbet
Space Writer
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
If these nearby stars hosted an exoplanet, here’s what it might be like
This artist’s impression shows a close-up view of Proxima d, a planet candidate recently found orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System.

Astronomers from ETH Zurich have predicted that an Earth-like planet could exist orbiting the nearest sun-like stars to Earth, called the α Centauri A/B binary. Though they weren't looking for direct evidence that such a planet exists, they were able to predict what it would be like if it did.

Most exoplanet research to date focuses on discovering exoplanets orbiting around distant stars, using techniques like the transit method which looks at dips in a star's brightness when a planet passes between it and us. From these small dips in brightness, researchers can calculate features like the size of a planet and how far it orbits from its star, and from this, they can infer things like the planet's surface temperature. The transit method tends to be good at spotting big exoplanets which orbit close to their stars, but less good for spotting smaller, Earth-sized planets.

Read more
This exoplanet has two suns – just like Tatooine
Artist's impression of Kepler-16b, the first planet known to definitively orbit two stars - what's called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA's Kepler mission.

A team of astronomers has detected a "Tatooine-like" exoplanet that orbits two stars. A person living on the planet would see two suns in the sky, like Luke Skywalker's home planet in Star Wars -- but unfortunately, it's a gas giant, so don't make any plans to build a house there.

The planet, known as Kepler-16b, is located 245 light-years away and was detected using a ground-based telescope at the Observatoire de Haute-Provence in France. A planet orbiting two stars is technically known as a circumbinary planet, and these are rarely discovered. They are interesting puzzles as it's not clear how such planets form. Typically, planets form from disks of matter around a single star, called protoplanetary disks, but this might not work in a system with two stars.

Read more
Hints of a planet in the habitable zone of a dead star
exoplanet habitable zone dead star white dwarf planetary debris

When you think of searching for habitable planets, you probably think about looking for Earth-like planets orbiting sun-like stars. But the range of possibly habitable planets is larger than that, and astronomers recently discovered indications of a planet in the habitable zone of a dead star.

When stars eventually run out of fuel, they first grow and cool to become red dwarfs, before losing the last of their hydrogen and shrinking and cooling further to become a white dwarf. This is what will eventually happen to our sun, as well as 95% of other stars. It's rare to find planets orbiting these white dwarfs, but recent research found indications of one such planet in the white dwarf's narrow habitable zone for the first time.

Read more