A team of astronomers has discovered a planet that is both closer and younger than any other Earth-sized world discovered so far. It's an extremely hot world that's very close to our own planet and sun-like stars, providing a unique opportunity to study how planets evolve.
HD 63433d, a newly discovered Earth-sized planet by astronomers, provides a rare glimpse into the early stages of planetary evolution as it orbits tightly around a young, sun-like star.
A new study recently published in The Astronomical Journal describes the new planet. Melinda Soares-Furtado, a NASA Hubble Fellow and UW-Madison professor of astronomy, and Benjamin Capistrant, a recent UW-Madison graduate and now a graduate student at the University of Florida, led the study along with authors from around the world.
"This is an interesting planet to study because it could be like early Earth," Soares-Furtado said.
The planet, known as HD63433d, is the third planet discovered orbiting a star called HD63433. HD63433d is so close to the star that it orbits it every 4.2 days.
"Even though its orbit is really close, we can use follow-up data to look for evidence of outgassing and atmospheric loss, which may be important constraints on how terrestrial worlds evolve," Soares-Furtado said. "But that's where the similarities end -- and they're striking."
Based on HD63433d's orbit, astronomers are relatively certain that it is tidally locked, meaning one side is always facing the star.
Temperatures on this side reach up to 2,300 degrees Fahrenheit and lava may flow out, while the other side is permanently dark.
What we should know about this planet's star:
HD63433 is roughly the same size and star type as our Sun, but (about 400 million years old) it is not even a tenth as old.
This star is approximately 73 light-years from our Sun and is part of a group of stars that move together to make up the constellation Ursa Major (home to the familiar Big Dipper). HD 63433 can be seen through a good pair of binoculars at night.
How did scientists discover this planet?
The study's authors are collaborating on a planet-hunting project called THYME. In 2020, they used data from NASA's Transiting Exoplanet Survey Satellite to discover two Neptune-sized planets orbiting HD63433.
Since then, the TESS satellite has observed the star four more times, collecting enough data to allow researchers to detect HD63433d crossing between the star and the satellite.
What's next?
Juliette Becker, a professor of astronomy at the University of Wisconsin-Madison, believes that HD63433d has a lot to learn from.
The planet is uniquely located for further study. Its young star is visible from both the southern and northern hemispheres, increasing the number of instruments that can train the system, such as the Large Telescope in South Africa or the WIYN Observatory in Arizona (both of which UW-Madison helped design and build).
The star, which is orders of magnitude closer than many stars Soares-Furtado has studied, may provide an opportunity to develop new methods of studying gas escaping from a planet's interior or measuring its magnetic field.
"It's kind of exciting that this is our solar backyard," Soares-Furtado said. "What kind of information does a star so close, with such a crowded system around it, provide? How will it help us as we continue to look for planets among the 100 or so other similar stars in this young cluster it belongs to?"