You’re on a camping trip with your family and your parents tell you to turn off all the lights. But, of course, your little brother wants to shine his flashlight directly at the sky saying aliens will see it. You finally get him to shut off his flashlight, and you give your eyes a few minutes to adjust to the darkness. As they do, more and more stars begin to appear in the night sky that were initially hidden beneath the glare of your (loser) brother’s flashlight. As the stars get brighter and increase in number, you start firing off a slew of questions in your head: How far away are they? Are there planets around them? What kinds of life are on those planets?

Now, NASA’s TESS (Transiting Exoplanet Survey Satellite) might be one step closer to answering those questions. This is because the long-running, exoplanet-hunting spacecraft recently released its all-sky mosaic depicting both the confirmed and candidate exoplanets it has identified since its science operations started in July 2018. The mosaic is comprised of blue and orange dots showcasing 679 confirmed and more than 5,165 candidate exoplanets, respectively.

Launched in April 2018, the goal of TESS was to serve as a successor to NASA’s Kepler Space Telescope, which conducted a primary mission from 2009 to 2013 and its follow-up K2 mission from 2014 to 2018. Kepler’s task was to focus on one patch of sky for several years to identify dips on starlight when exoplanets pass in front of their host stars, also called a transit. This patch of sky is estimated to be equivalent to your entire fist stretched out at arm's length, or 0.25 percent of the entire sky.

When two of Kepler’s stabilizing reaction wheels broke, preventing Kepler from steering, the mission was redesignated as K2, which observed several patches of the sky. In the end, both missions successfully confirmed the existence of more than 3,000 exoplanets and another 3,000 exoplanet candidates. Essentially, TESS unofficially combined the Kepler and K2 missions into a single mission as it has spent almost the last eight years scanning the entire heavens with the goal of identifying transiting exoplanets.

“Over the last eight years, TESS has become a fire hose of exoplanet science,” said Dr. Rebekah Hounsell, who is a TESS associate project scientist at the University of Maryland Baltimore County and NASA’s Goddard Space Flight Center. “It’s helped us find planets of all different sizes, from tiny Mercury-like ones to those larger than Jupiter. Some of them are even in the habitable zone, where liquid water might be possible on the surface, an important factor in our search for life beyond Earth.”

A key TESS discovery was the TOI-700 system, which TESS first identified and whose findings were later confirmed with ground-based telescopes. The TOI-700 system is located approximately 100 light-years from Earth with TESS successfully identifying three exoplanets, TOI-700 b, c, and d, and all of which are approximately Earth-sized, with TOI-700 d estimated to be orbiting within its host star’s habitable zone. With the host star being a red dwarf star, which is smaller and cooler than our Sun, scientists estimate that TOI-700 d gets approximately 86 percent of the solar radiation that Earth gets from our Sun.

Another key discovery was TOI-1338 b, which was the first circumbinary exoplanet discovered by TESS, which are exoplanets that orbit two stars, with the stars in the TOI-1338 system being an F-type star at approximately 10 percent larger than our Sun and a smaller M-dwarf (red dwarf) star.

While TESS has been operating since mid-2018, it has received funding for several extended missions, with a recent article published in Space Science Reviews noting how TESS’ third extended mission is slated to run until at least September 2028.

What new insights into exoplanets will TESS give scientists in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!