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MIT mission discovers an Earth-sized planet orbiting a nearby star

A SpaceX Falcon 9 rocket lifted off in April 2018 from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, carrying NASA's Transiting Exoplanet Survey Satellite (TESS). NASA/Tony Gray

Scientists using a satellite space telescope to look for the shadows of planets passing in front of stars have discovered an Earth-sized planet orbiting a nearby star 52 light-years from Earth, MIT said Tuesday.

The new planet, HD 21749c, orbits the star HD 21749. It circles the star in 7.8 days, an MIT-led team of astronomers found. The planet is probably rocky and uninhabitable, with temperatures on the surface of up to 800 degrees, MIT said.

The planet was discovered by NASA’s Transiting Exoplanet Survey Satellite, or TESS, a NASA Astrophysics Explorer mission operated by MIT.

The discovery is detailed Tuesday in a paper published in the journal Astrophysical Journal Letters.


TESS launched on April 18, 2018, aboard a SpaceX Falcon 9 rocket with a mission of finding planets outside our solar system, including those that could support life.

It was the first Earth-sized exoplanet discovered by TESS, and it’s the smallest it’s discovered.

“For stars that are very close by and very bright, we expected to find up to a couple dozen Earth-sized planets,” says lead author and TESS member Diana Dragomir, a postdoctoral researcher in MIT’s Kavli Institute for Astrophysics and Space Research.

“And here we are — this would be our first one, and it’s a milestone for TESS. It sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable.”

A test picture taken by one of the four TESS cameras about a month into the mission. More than 200,000 stars are visible. The bright star at the bottom center is Beta Centauri.NASA/MIT/TESS

TESS is designed to circle Earth while pointing its four cameras outward, covering nearly the entire sky.

The telltale sign of an exoplanet is a dip in starlight as it passes in front of, or “transits,” its host star.

Over a two-year mission, TESS aims to find for the astronomy community at least 50 small, rocky planets and estimate their masses, the university said. So far, it has found 10 planets smaller than Neptune.


The researchers had previously found a “sub-Neptune” planet also orbiting HD 21749, every 36 days. They decided to pore over the data again to see whether there were any other signs of planets circling the same star.

“We know these planets often come in families,” Dragomir says. “So we searched all the data again, and this small signal came up.”

Other Earth-sized exoplanets have been discovered in the past. NASA’s Kepler Space Telescope, now retired, looked at more than 530,000 starts and ultimately found 2,662 planets, many of them Earth-sized, MIT said. A handful were even seen to have conditions that might be amenable to developing life.

Technicians dressed in clean room suits worked on TESS with its solar panels deployed at the Kennedy Space Center in Florida in February 2018. NASA/Leif Heimbold