NASA Discovers Earth-sized Planet With ‘Lava Hemisphere’

HOUSTON, TX - Astronomers using data from NASA's Transiting Exoplanet Survey Satellite (TESS) have identified a new planet in the HD 63433 planetary system. 

This system, initially known for two planets, revealed a third, extra hot, and Earth-sized planet transiting in front of its Sun-sized star.

The newly-found planet, named HD 63433 d, is a tidally locked exoplanet, meaning one side constantly faces its star, while the other remains in perpetual darkness. 

Orbiting around the star HD 63433 in a system about 400 million years old, HD 63433 d is the smallest confirmed exoplanet of its kind in this age range. 

According to NASA, this scorching world is the smallest confirmed exoplanet younger than 500 million years old. It's also the closest discovered Earth-sized planet this young, at about 400 million years old.

Utilizing TESS data, a team of astronomers, led by co-authors Benjamin Capistrant and Melinda Soares-Furtado, analyzed the system. By filtering out signals from the two known planets, they uncovered a subtle transit occurring every 4.2 days, subsequently confirming the presence of a third, smaller planet in the system.

HD 63433 d, approximately 1.1 times the diameter of Earth, orbits a G-type star, similar to our Sun. However, its year is incredibly short, lasting a mere 4.2 days, resulting in scorching temperatures on its dayside. With an age of around 400 million years, the planet is significantly younger than Earth, and its close proximity to the star raises questions about its atmosphere.

Despite its size and proximity to a sun-like star, HD 63433 d is markedly distinct from Earth.

The planetary system itself is about 10 times younger than ours, and the planet's extreme closeness to its star results in temperatures on the dayside reaching approximately 2,294 Fahrenheit, information from NASA stated. 

The combination of the planet's small size, young age, and proximity to its star makes it a compelling subject for further exploration. A follow-up study could offer insights into the planet's "dark side" and potentially unveil details about its atmosphere, as young terrestrial worlds play a crucial role in advancing our understanding of planetary formation and evolution.

This discovery is detailed in a study titled "TESS Hunt for Young and Maturing Exoplanets (THYME) XI: An Earth-sized Planet Orbiting a Nearby, Solar-like Host in the 400 Myr Ursa Major Moving Group." The study is set to be discussed in a presentation at the 2024 American Astronomical Society Meeting.