Astronomers spot Earth-sized planet with ‘lava hemisphere’

In a system that includes two known planets, astronomers have spotted something new: a small object transiting through the sun-sized star. It turned out to be another planet, very hot and the size of Earth.

The newly spotted planet, called HD 63433 d, is tidally locked, meaning there is a day side that always faces its star and a side that is constantly in darkness. This exoplanet, or planet outside our solar system, orbits the star HD 63433 (TOI 1726) in the planetary system HD 63433. This hot world is the smallest confirmed exoplanet less than 500 million years old. It is also the closest Earth-sized planet discovered this young, around 400 million years old.

A team of astronomers analyzed this system using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), which tracks “transits” or cases where planets pass each other in front of their star during their orbit, blocking a tiny piece of starlight. Two planets had already been discovered in this planetary system. To see what might be lurking in the star’s orbit, the team took the data and removed signals from the two known planets. This allowed them to see an additional signal: a small transit that reappeared every 4.2 days. After further investigation, they were able to confirm that it was actually a third, smaller planet.

The tidally locked planet is very close to the size of Earth (it’s about 1.1 times the diameter of our own planet) and it orbits a star that is similar to the size of our sun (the star is approximately 0.91 times the size and 0.99 the mass of the sun). sun).

The star in this system is a G-type star, the same type as our sun. But HD 63433 d orbits much closer to its star than us, with a tiny “year” of 4.2 days and extremely high temperatures on its day side.

Although this newly discovered planet and its star are roughly the size of our planet and sun, HD 63433 d is quite different from our home world.

First, it’s a very young planet in a very young system. The planetary system itself is about 10 times younger than ours and this 400 million year old planet is in its infancy compared to our 4.5 billion year old world.

It is also much closer to its star than we are to ours. This planet is eight times closer to its star than Mercury is to the sun. Being so close to its star, the dayside of this tidally locked planet can reach temperatures of around 2,294°F (1,257°C). Being so hot, so close to its star, and so small, this planet likely lacks a substantial atmosphere.

These scorching temperatures are comparable to lava worlds like CoRoT-7 b and Kepler-10 b, and the team behind the discovery believes the planet’s dayside could be a “lava hemisphere.”

The planet’s small size, young age and proximity to its star make it an interesting candidate for further exploration. A follow-up study could confirm the results of this study and potentially reveal more information about the “dark side” of the planet and the state of its (possible) atmosphere. As this study states, “young terrestrial worlds are essential test beds for constraining prevailing theories of planetary formation and evolution.”

This discovery was described in a new study, published in the The astronomical journal, titled “TESS Hunt for Young and Maturing Exoplanets (THYME) The study, led by co-authors Benjamin Capistrant and Melinda Soares-Furtado, was discussed in a Jan. 10 presentation at the 2024 meeting of the American Astronomical Society.

This study was carried out as part of the TESS Hunt for Young and Maturing Exoplanets, a project focused on the search for young exoplanets belonging to moving groups, stellar associations or open clusters.