NASA’s TESS discovers its first Earth-size planet

  • llustration of NASA's Transiting Exoplanet Survey Satellite:TESS. (NASA's Goddard Space Flight Center/TNS)

NEW YORK — NASA’S Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet.

The planet, named HD 21749c, is around 89% of Earth’s diameter, and is 53 light-years away. Its surface is likely rocky and hot, with temperatures that could reach up to 800 degrees Fahrenheit.


The Earth-size planet likely orbits the K-star HD 21749, which is around 70% of the size of the sun. It circles very close to its star, and likely takes a little under eight days to orbit.

This is the 10th planet discovered by TESS, and the second in the southern constellation Reticulum where HD 21749c and the K-star are located.

TESS also discovered a planet called HD 21749b, which completes orbit in 49 days, as stated in a report on the discovery published in the journal, The Astrophysical Journal Letters. The mini Neptune-like planet completes orbit in around 36 days.

Scientists from the Massachusetts Institute of Technology and the Carnegie Institution for Science used transit data from the first four sectors of TESS’ observations and noticed 11 “periodic dips in the star’s brightness,” indicating the presence of a planet.

Launched April 18, 2018, on a SpaceX Falcon 9 rocket, TESS will survey 200,000 of the brightest stars closest to the sun in search of planets over a two-year period, according to NASA.

The mission divides the area of the sky into 26 sectors, which are 24 degrees by 96 degrees across. Of the thousands of planet candidates, around 300 are expected to be “Earth-sized and super-Earth sized exoplanets,” according to NASA.


The report on the discoveries called the system a “prime target” for comparative studies on planet and system makeup.

Follow-up studies “could provide critical information about the planet’s properties, including potentially the first mass measurement of an Earth-size planet found by TESS,” a statement said.

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