NASA’s TESS Mission Discovers an Exoplanet of Molten Iron

Astronomers have discovered well over 4,000 exoplanets with the help of instruments like the dearly departed Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS). That latter mission just detected yet another planet, but this one is a bit unusual.

According to a new study in the journal Science, the planet known as GJ 367 b appears to be almost entirely composed of super-hot iron. This molten world could, in the near future, help us understand some confounding aspects of our own solar system.

GJ 367 b orbits a red dwarf star 31 light years away from Earth. Like Kepler, TESS is not designed to directly image exoplanets — that’s still impossible with current technology in all but a few cases. TESS observes vast starfields in search of dimming events that could be the result of a planet transiting in front of a star. With repeated observations, it’s possible to identify an exoplanet’s size, location, and even some elements of its composition.

In the case of GJ 367 b, astronomers believe its high density could mean it’s an analog to the planet Mercury, which is rich in iron. These types of stars are smaller and cooler than our sun, but GJ 367 b orbits very close, completing a revolution every 7.7 hours. Astronomers estimate the surface temperature on the alien world is 1500 degrees Celsius (about 2700 degrees Fahrenheit). That’s close to the melting point of iron, ensuring the planet’s surface is thoroughly inhospitable.

According to the team of international researchers who analyzed the TESS data, it’s unlikely that GJ 367 b formed in its current location. Temperatures are so high that primordial space debris wouldn’t have been able to stick together. So, the planet may have formed elsewhere and migrated inward. Understanding where it came from could help us puzzle out the history of Mercury. At this point, scientists don’t know why Mercury is so much richer in iron than the other inner planets. Some believe Mercury was struck by a large object in the distant past that blew away most of its crust, leaving an iron core with a thin layer of rock.

The latest exoplanet discovery offers a fascinating piece of evidence, but it won’t definitively answer any questions until we can get a better look at it. Its location, a mere 31 light years away, is close in the grand scheme of the universe. Astronomers believe the upcoming James Webb Space Telescope might be able to image the planet from its vantage point on the far side of the moon. NASA plans to launch Webb later this month after years of delays.

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