TESS first light

NASA’s TESS Hunt for Exoplanets Notches First Candidates

NASA’s Transiting Exoplanet Survey Satellite (TESS) officially began scouring the sky for exoplanets last month. Today, astronomers announce the first of what is expected to be 20,000 new exoplanets.

Pi Mensae c will probably go down as TESS first exoplanet discovery. I say probably because the discovery is now being reviewed by other scientists (and telescopes) to confirm it.

This exoplanet is a super-Earth at about 2.14 times the Earth’s radius and 4.82 times the mass. It orbits a bright yellow dwarf star called Pi Mensae, or HD 39091.

As for the prospects of life? That’s not in the cards for Pi Mensae c. A year on this exoplanet (one full orbit around its star) lasts just 6.27 days. Way too close to a bright star to support life as we know it.

An early look at the data suggests Pi Mensae c has a rocky, iron core along with water, methane, hydrogen, and helium.

“TESS has begun to fulfill its promise to enlarge the collection of small, transiting planets orbiting bright stars. Such stars enable precise measurements of that planet’s mass and radius,” the authors write in their paper.

TESS used the same technique as Kepler, and other telescopes use to spot far away exoplanets – transits. Astronomers look for regular dips in a star’s brightness to detect planets. Follow-up observations showing the same drops happening at regular intervals confirms these candidates into exoplanets. Here’s what TESS saw with Pi Mensae c.

pi mensae c transit

That’s the dip TESS is looking for.

Another paper published this week highlights a different exoplanet discovered by TESS. The authors describe a “hot Earth” around LHS 3844, an M dwarf star about 50 light years away. This exoplanet is 1.32 times larger than Earth and cruises around LHS 3844 every 11 hours.

Here’s the tell-tale dip in brightness.

hot earth transit

Transits of this “hot Earth” were also seen via ground-based telescopes. The El Suance Observatory in El Sauce, Chile along with the Las Cumbres Observatory observed transits earlier this month.

TESS is more surveyor than telescope. While Kepler looked at tiny pieces of the sky, TESS will soak in huge slices of it. More than 200,000 of the brightest dwarf stars will be monitored over the next two years. I mentioned the survey is expected to find 20,000 exoplanets, but a decent chunk of them will be closer to Earth-sized. Astronomers are expecting about 50 Earth-sized planets to be discovered with up to 500 less than twice the size of Earth like the “hot Earth” above according to NASA.

TESS can give us details like the size of the planet and how long its orbit is. Follow-up observations from telescopes on the ground give astronomers the mass. Slap the two data points together we learn what the density of the exoplanet is. Which then can tell us if it’s a wet, rocky, or gas world.

Today, we’ve added two potential exoplanets to the list of already discovered worlds. If everything goes smoothly, TESS will add about 20,000 more before it’s mission is complete.

Top image: First light from TESS

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