Nasa’s new "Tess" space telescope is to set out in search of new planets. Its particular interest is in "red dwarfs."
It was the first time that Nasa used the services of space company SpaceX for a scientific mission Photo: dpa
Millions of stars in the sky get a new overseer: The space telescope "Tess" of the U.S. space agency Nasa launched on Wednesday (local time) for its mission. The spacecraft will search for new planets around the nearest and brightest stars. Future telescopes could then search for extraterrestrial life in these new worlds.
In doing so, "Tess" will explore the galaxy even more thoroughly than its predecessor "Kepler". "We’re going to look at every single one of these stars," explains lead scientist George Ricker of the Massachusetts Institute of Technology (MIT). Experts expect the new telescope to detect thousands of so-called exoplanets outside our solar system.
"All astronomers in the coming centuries will be focused on these objects," Ricker says. "This is really a mission for the ages." Nasa Director of Astrophysics Paul Hertz says missions like "Tess" will help answer the question of whether humanity is alone in space – or just lucky enough to have "the best luxury property in the galaxy."
"Tess" stands for "Transiting Exoplanet Survey Satellite" and is the successor to the highly successful "Kepler" space telescope, the pioneer of planetary counting. After nine years of flight, "Kepler" is now running out of fuel. Nasa expects the device to last a few more months at best.
50 exoplanets could be habitable
In the course of its mission, "Kepler" alone has discovered more than 2600 confirmed exoplanets. More candidates are still awaiting recognition. The number of extrasolar planets counted in recent decades by all observatories in space and on Earth is more than 3700, and another 4500 candidates have a good chance.
About 50 exoplanets could possibly be habitable, according to scientists. They have the necessary size and the right orbit of their star to allow surface water and – at least theoretically – life.
However, most of the planets identified by "Kepler" are so far away that huge telescopes would be needed to study them more closely. For this reason, astronomers now want to focus on much brighter stars that are closer to Earth – so that in the future the planned Nasa telescope "James Webb" can take a closer look at the atmospheres of surrounding planets. The observations will also involve powerful telescopes on the ground, as well as large observatories that so far exist only on the drawing board.
MIT astrophysicist Sara Seager, who is dedicated to the search for a second Earth, already envisions water worlds waiting to be explored. Perhaps they are hot super-Earths with lakes of molten lava, or rocky or icy planets with thin atmospheres similar to Earth’s, she says. But looking at recent science fiction films, she also stresses, "We’re not at ‘Interstellar’ or ‘Arrival.’ Not yet, anyway."
The light of the stars is decisive
After launching from the Cape Canaveral Space Center aboard a Falcon 9 rocket built by the private space company SpaceX, "Tess" is expected to enter an orbit that reaches as far as the moon. "That’s a big thing, and we’re really excited about that," Ricker says. Yet the $337 million (270 million euro) spacecraft is relatively small, weighing 362 kilograms and measuring 1.2 by 1.5 meters.
The four cameras of "Tess" will focus on red dwarfs in the cosmic backyard – on average, they are ten times closer to Earth than the stars observed by "Kepler." Most of them are 300 to 500 light-years away, according to Ricker. One light year equals about nine trillion kilometers.
Red dwarfs are the most common class of stars and, as their name implies, are relatively small – no more than half the size of our sun. However, they are also comparatively cool. For example, the celebrated star system Trappist-1 is an extremely cold red dwarf and only slightly larger than Jupiter. It is orbited by at least seven Earth-like planets.
But how will the new telescope detect a planet from so far away in the vicinity of such a small, faint star? The light from the stars is crucial: when a planet passes by, it dims briefly. "Tess" will register any such luminous sign.
If other life should be found
The telescope will monitor almost the entire sky. It will begin with the Southern Hemisphere in the first year and the Northern Hemisphere in the second. More years of observation could follow. "Tess" will not look for atmospheric or other signs of life, Nasa and others point out, because it is not technically capable of doing so.
That task is left to "Webb," the successor to the "Hubble" telescope. Nasa has postponed its launch until at least 2020.
If life is indeed found – be it microscopic or in a higher form – scientists plan to send research robots into space for closer inspection.
But the technology to do so does not yet exist, as Nasa project manager Jeff Volosin points out. "To me, just knowing they’re there would be enough," he says of possible alien life forms. "To know that we’re not alone."