SpaceX blasts off NASA's new planet-hunter, TESS

"Three, two, one and liftoff!" said a NASA commentator as the Transiting Exoplanet Survey Satellite (TESS) soared into the blue sky atop a SpaceX Falcon 9 rocket from Cape Canaveral, Florida at 6:51 pm (2251 GMT).

The washing machine-sized spacecraft is built to search outside the solar system, scanning the nearest, brightest stars for signs of periodic dimming. These so-called "transits" may mean that planets are in orbit around them.

TESS is expected to reveal 20,000 planets beyond our solar system, including more than 50 Earth-sized planets and up to 500 planets less than twice the size of the Earth, NASA said.

Its discoveries will be studied further by ground- and space-based telescopes for signs of habitability, including a rocky terrain, a size similar to Earth and a distance from their sun -- neither too close nor too far -- that allows the right temperature for liquid water.

"The stories of these planets will continue on, long after their detection," Martin Still, TESS program scientist, said Wednesday.

TESS will survey far more cosmic terrain than its predecessor, NASA's Kepler Space Telescope, which launched in 2009.

Both use the same system of detecting planetary transits, or shadows cast as they pass in front of their star.

The new spacecraft will focus on nearby exoplanets, within a dozen to 100 light-years away.

Kepler's trove of more than 2,300 confirmed planets outside our solar was impressive, but most were too distant and dim to be examined further.

"One of the many amazing things that Kepler told us is that planets are everywhere and there are all kinds of planets out there," said Patricia "Padi" Boyd, director of the TESS guest investigator program at NASA's Goddard Spaceflight Center.

"So TESS takes the next step. If planets are everywhere, then it is time for us to find the planets that are closest to us orbiting bright nearby stars, because these will be the touchstone system."

The Hubble Space Telescope and the James Webb Space Telescope, scheduled to launch in 2020, should be able to reveal more about planets' mass, density and the makeup of their atmosphere -- all clues to habitability.

The initial attempt Monday was scrubbed about two hours before planned takeoff, so that SpaceX engineers could perform extra checks on the rocket's navigation systems.

On Wednesday, the rocket performed flawlessly.

Less than 10 minutes after launch, the rocket's first stage returned to an upright landing on a drone ship in the Atlantic Ocean, marking SpaceX's 24th touchdown of a rocket booster.

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