As of this afternoon, astronomers have discovered 3,758 planets around other stars. Staggering, isn’t it? In the not too distant future, that number will sound like peanuts. NASA’s Transiting Exoplanet Survey Satellite or TESS will soon become the first-ever spaceborne, all-sky planet surveyor and add at least 1,500 more.
The spacecraft is scheduled to launch on Monday, April 16 from Cape Canaveral Air Force Station in Florida on a SpaceX Falcon 9 rocket. Liftoff will be broadcast on NASA-TV. TESS follows in the footsteps of the Kepler Space Observatory, the first orbiting telescope dedicated to finding extrasolar planets. Its primary focus was a relatively small part of the sky in the direction of Northern Cross.
TESS will seek planets ranging from Earth-sized to Jupiter-sized gas giants across the entire sky with a principle goal of finding and studying small planets in the “habitable zones” of nearby stars. Habitable means the planet is at the right distance from its host star for liquid water to exist on its surface. Although life may thrive in other habitats, to our best knowledge, it requires water.
TESS will monitor more than 200,000 stars during its two year mission, searching for temporary drops in brightness caused by planetary transits. A transit occurs when a planet’s orbit carries it directly in front of its parent star as viewed from Earth. Some of you may have seen one or both transits of Venus a few years back, when the planet looked like a black dot crossing the sun’s face. If you had used a very sensitive light meter, you could have measure how much Venus had dimmed the sun during its passage. TESS will uses its four cameras to+ look for tiny dips in the brightness of a star when its planet(s) cross in front.
More on TESS, its unique orbit and how the probe will send its findings back to Earth
Once detected, the size of the planet’s orbit can be calculated from how long it takes the planet to orbit once around the star. Its mass can be found using Kepler’s Third Law of planetary motion and its size from the depth of the transit or how much the star’s brightness drops. From the orbital size and the temperature of the star, we can get an idea of the planet’s temperature and make a reasonable guess as to whether it might be suitable for life.
TESS is expected to spy more than 1,500 exoplanet candidates, including about 500 Earth-sized and ‘Super Earths’ — planets more massive than Earth but smaller than Uranus and Neptune. Once they’re identified by TESS, astronomers will use other telescopes to detect to study the planets’ atmospheres and weather.