Hidden within a faraway solar system, astronomers have discovered a planet that is entirely lava on one side.
The planet, named HD 63433 d, is the third to be found orbiting the star HD 63433 (TOI 1726), situated around 73 light years away from Earth. It was spotted by NASA recently as it passed in front of the star, according to a new paper in the Astronomical Journal.
This planet is surprisingly young at only 400 million years old and is around the same size as Earth. Its star scorches it to such a degree that the side facing it reaches temperatures up to 2,294 degrees Fahrenheit and could even be a "lava hemisphere."
It was the third to be discovered in the star system, having been hidden until it was spotted passing in front of its star by NASA's TESS (Transiting Exoplanet Survey Satellite). This measures tiny drops in the brightness of stars caused by planets passing across them and is one of the main ways exoplanets are discovered. HD 63433 d was noticed when astronomers saw the brightness of its star dipping once every 4.2 days.
"We noted the repeating dimming of the star as each of the exoplanets passed in front of the line of sight of the star. The newest planet, HD 63433 d, dims the star by just 100 parts per million (100/1.0E6 mag)," Melinda Soares-Furtado, study co-author and NASA Hubble postdoctoral fellow at the University of Wisconsin-Madison and Massachusetts Institute of Technology, told Newsweek.
HD 63433 d is around 1.1 times the mass of Earth, making it similar in structure to our home world, and its star is about the same mass and about 0.91 times the size of our sun. This is where the similarities with our solar system end, as HD 63433 d orbits its star at a distance eight times closer than Mercury orbits our sun, completing an orbit once every 4.2 days. The planet is tidally locked, meaning that only one side ever faces its star, and the other eternally faces away, just like the moon and the Earth.
On the side facing the star, the planet is scorched to the point half the planet may just be lava. Exoplanets, including CoRoT-7 b and Kepler-10, are thought to also be lava worlds due to the intense heat they face from their star. HD 63433 d likely doesn't have much of an atmosphere due to the high temperatures.
"A planet needs to be hotter than ~2000 F (1500 K) to have all the minerals in molten form. The dayside temperature of this planet does exceed this threshold (T=1530 K)," Soares-Furtado said.
This planet is also only around 400 million years old, around 10 times younger than our 4-billion-year-old planet. This discovery is, therefore, hoped to allow astronomers to study the formation of a world like ours and how it's influenced by extreme heat.
"The significance of the young age is that this system provides a test case for a young Earth-sized world. For example, early Earth is known to have an extended atmosphere (composed primarily of hydrogen and helium) that made the planet 2x the size it is today," Soares-Furtado said.
"Investigating early Earth-sized planets can help us understand how these rocky worlds lose their atmospheres and the rate at which this occurs for planets with varying orbital architectures. Our team is actively working to find more young exoplanets in our Solar backyard for this very purpose."
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Update 1/18/24, 12:18 p.m. ET: This article was updated with comments from Melinda Soares-Furtado.
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
