TESS exoplanet search to start next week

The satellite will launch on a SpaceX rocket

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Artist's Concept of TESS searching for exoplanets close to the brightest stars near our solar system.

The Transiting Exoplanet Survey Satellite (TESS), an MIT-led NASA mission, is scheduled to launch no earlier than April 16 (6:32 EDT) from the Cape Canaveral Air Force Station on a SpaceX Falcon 9 rocket. When it does, it will begin the latest chapter in the search for new worlds.

Over the course of the next 2 years, TESS will monitor more than 200,000 stars (particularly small ones) across the entire sky by looking for the characteristic dip in brightness of a host star caused by planetary transits. In an interview with The Tech, TESS Deputy Science Director and  professor of EAPS and Aeronautics and Astronautics Sara Seager likened the transit method to “find[ing] an ant in front of a glaring, glaring searchlight.” Smaller stars have a lower energy output, and as a result will give rise to stronger transit signals from small planets. TESS will look for dips in brightness in a patch of stars over a period of 27 days. There are several reasons for the small periods, according to Seager. Smaller stars have smaller habitable zones, and due to Kepler’s Third Law, planets within these small habitable zones will have periods of around 10–30 days.

It is important to note, however, that TESS will be looking for planet candidates. Dips in brightness similar to those of exoplanets can be caused by other factors such as spots and interference from other stars. An exoplanet designation will require follow-up teams and confirmation from other telescopes, Seager said.

And while computers will do most of the work in processing the data, human eyes will play a major role in the actual exoplanet finding. According to Seager, “Computers will only do what you tell it to do. And we’ll be looking at a lot of the data ourselves. It sounds rather old-fashioned, but the human eye is still really wonderful at pattern recognition. Especially looking for crazy things you might not have expected. That you might not have told your algorithm to search for.”

TESS comes from a long line of space- and ground-based telescopes tasked with searching for worlds orbiting stars other than our own. A celebrity in the exoplanet hunting business is the Kepler Space Telescope, which has found thousands of confirmed exoplanets since its launch in 2009. Due to the failure of its second gyroscope in 2013, Kepler now operates under the K2 mission and uses solar wind to stabilize itself to periodically focus on different regions in the sky.  

TESS has had a long history of its own. Conceived over a decade ago by Professor George Ricker of the Kavli Institute, TESS has been rejected from competitions, passed over for other missions, and seen donors come and go. It took winning the NASA Explorer (EX) Class Mission in 2010 for TESS to reach this point.

Professor Seager says that she is “confident” that TESS will launch on the first possible day next week.