NASA Is Launching Its Next Planet-Hunting Telescope, Here's What to Know

NASA is planning to launch its next telescope into space on Monday during a window that opens at 6:32 p.m. Eastern time. The instrument, called the Transiting Exoplanet Survey Satellite and nicknamed TESS, is designed to identify thousands of exoplanets. Scientists are excited about the prospect the mission holds for new discoveries, but if you're just learning about the mission now, here's what you need to know.

TESS is the successor to Kepler, which revolutionized exoplanet science and is responsible for spotting almost three quarters of the planets astronomers have identified to date. But Kepler will run out of fuel sometime in the next few months, so scientists have been working for years to make sure something would be ready to replace it.

The new mission was inspired by Kepler's approach to spotting exoplanets, although planning for TESS began before Kepler even launched. Both telescopes are designed to spot the tiny dips in a star's brightness as a planet passes between the telescope and the star.

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Kepler's main mission did that for a specific patch of stars, staring at the same section of the sky constantly. Instead, TESS is designed to cover the whole sky in 26 different segments. "One of the things that had never really been done in space was a comprehensive search for transits," TESS scientific leader George Ricker, an astronomer at MIT, told Newsweek.

But TESS is still targeting a specific subset of stars: It is focused on small bright stars that are fairly close to Earth. "This will really be the first time that many of these really bright stars, that have names, that we know and love, will be surveyed for variations," Ricker said.

An artist's conception of what TESS will look like in action. NASA's Goddard Space Flight Center

There's also a practical reason for prioritizing planets located around these bright stars. They will be easiest for astronomers to study again with the even higher-powered telescopes they'll need to start understanding what the planets look like—and, for example, whether they might be attractive to life.

Those planets will be quite close to their star, since TESS will need to spot them orbit multiple times in a given 27-day-long survey of a specific sky segment. According to the predictions mission scientists have made for the telescope, it should be able to find about 20,000 exoplanets, of which dozens should be about the size of Earth. "It's a huge crop of planets," Ricker said.

TESS will hitch a ride on a Falcon 9 rocket and should begin observations about two months after its arrival in space. The survey is scheduled to last two years, although the telescope will be able to stay in its orbit for decades so NASA could easily extend its mission.