Introducing Tess, the seeker of alien worlds
Astronauts are sending the little spacecraft to find planets close enough to scrutinise with telescopes or for habitability
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The search for cosmic real estate is about to begin anew. No earlier than 6:32pm on April 16, in NASA’S fractured parlance, a little spacecraft known as the Transiting Exoplanet Survey Satellite, or TESS, bristling with cameras and ambition, will ascend on a Spacex Falcon 9 rocket in a blaze of smoke and fire and take up a lengthy residence between the moon and the Earth.
There it will spend the next two years, at least, scanning the sky for alien worlds.
TESS is the latest effort to try to answer questions that have intrigued humans for millenniums and dominated astronomy for the past three decades: Are we alone? Are there other Earths? Evidence of even a single microbe anywhere else in the galaxy would rock science.
Not so long ago, astronomers did not know if there were planets outside our solar system or, if there were, whether they could ever be found. But starting with the 1995 discovery of a planet circling the sunlike star 51 Pegasi, there has been a revolution.
NASA’S Kepler spacecraft, launched in 2009, discovered some 4,000 possible planets in one small patch of the Milky Way near the constellation Cygnus. Kepler went on to survey other star fields only briefly after its pointing system broke. After nine years in space, it’s running out of fuel.
Thanks to efforts like Kepler’s, astronomers now think there are billions of potentially habitable planets in our galaxy, which means the nearest one could be as close as 10 to 15 light-years from here.
And so the torch is passed. It’s now TESS’ job to find those nearby planets, the ones close enough to scrutinise with telescopes, or even for an interstellar robot to visit.
“Most of the stars with planets are far away,” said Sara Seager, a planetary scientist at the Massachusetts Institute of Technology and a member of the TESS team, referring to Kepler’s bounty. “TESS will fill in planets around nearby stars.”
George Ricker, an MIT researcher and the leader of the TESS team, expects to find some 500 Earth-size planets within 300 light-years of here, close enough for a coming generation of telescopes on the ground and in space to examine for habitability — or perhaps even inhabitants.
But there will be more than planets in the universe, according to TESS.
“TESS is going to be a lot of fun,” Ricker said. “There are 20 million stars we can look at.” The spacecraft will be able to do precise brightness measurements of every glint in the heavens, he said. “Galaxies, stars, active galactic nuclei,” his voice trailing off.
Most of the exoplanets will be orbiting stars called red dwarfs, much smaller and cooler than the sun. They make up the vast majority of stars in our neighbourhood (and in the universe) and presumably lay claim to most of the planets.
Like Kepler, TESS will hunt those planets by monitoring the light from stars and detecting slight dips, momentary fading indicating that a planet has passed in front of its star.
The mission’s planners say they eventually expect to catalogue 20,000 new exoplanet candidates of all shapes and sizes. In particular, they have promised to come up