The spaceship will search almost the entire sky for neighboring stars, searching for the dips in their brightness that signal the presence of a planet. The goal: to find planets smaller than Neptune, with a radius about four times that of Earth.
On a cold, clear night in January, astrophysicist George Ricker and his students entered a rooftop campus and pointed a camera at the highest point in the sky.
This camera, an engineering model of the four launched with NASA's TESS mission, revealed a night so dense with stars that they obscured the normally different constellations. 19659003] "In two seconds you could see things that were one hundred thousand to one million times weaker than what you could see with the naked eye," said Ricker, the mission's lead investigator.
The test provided a little foretaste TESS, the Transit Exoplanet Survey Satellite, will discover. The spaceship, launched on Wednesday with a SpaceX Falcon 9 rocket, will search almost the entire sky for nearby stars and search for the dips in their brightness that signal the presence of a planet.
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The goal: to find planets smaller than Neptune, with a radius about four times that of the planet Earth. The scientists will then use other telescopes to measure the masses of 50 of them.
Some of the world's TESS finds may be small, rocky bodies, like the Earth. And some of these could possibly be habitable places of life as we know it.
"It's very exciting," Ricker said. "We get the chance to answer a question that humanity has always been interested in: what is in the sky, and are there other beings, other places like the earth?"
For decades, astronomers have been searching for planets outside ours solar system.
Some of her first discoveries were confirmed in the 1990s. Among them were exoplanets discovered by ground-based telescopes, looking for the periodic wobble in the motion of a star caused by a planet's tiny tug-a technique known as the radial-velocity method. Others were found by searching for variations in the predictable rhythms of pulsars.
About 325 exoplanets were discovered when NASA launched the Kepler Space Telescope in 2009. She used the transit method and stared deep into a patch of sky for the shadows cast by the planets as they moved in front of their stars.
Kepler was a full-time planet hunter and revolutionized astronomers' understanding of exoplanets. It was particularly interested in finding earth-sized planets orbiting sun-like stars at a distance where water on the surface could be stable in liquid form – the so-called habitable zone.
To date, data from the primary mission have turned 2,343 confirmed and 2,244 candidate exoplanets, revealing that there could be more planets than stars in the Milky Way. Many of them are in multi-planet systems, and a large part of them seem to be super-Earths – a class larger than our planet but smaller than Neptune.
TESS, of the NASA Goddard Space Flight Center in Greenbelt, Maryland, will take the torch that Kepler set fire to.
Kepler stared only at a small patch of sky whose stars are up to 3000 light-years away. This made it difficult to conduct follow-up examinations with other telescopes.
TESS, on the other hand, targets stars that are less than 300 light-years away – and it will look in almost all directions.
"Kepler took a survey of stars in the galaxy to find out which planets they host," said Natalie Batalha, Kepler's project scientist at the NASA Ames Research Center. "TESS gets to know the neighbors."
It will do this with four cameras, each focused on a different part of the sky. Together, the cameras will look at a vertical strip of the celestial sphere that extends from the pole to the equator and progresses to a new stripe every 27 days.
TESS will watch for the regular loss of brightness from a planet in front of its stellar host and block a tiny amount of starlight. The larger the planet relative to its star, the deeper the drop. The more frequently these break-ins occur, the shorter is the orbit of a planet and the closer it is to its star. Scientists must observe these moods several times before they can see if it is indeed a circling world.
It will take about a year to study the sky over the southern hemisphere and another year to complete the northern hemisphere. At the end of its two-year mission, it will have represented about 85 percent of the sky. Astronomers believe that TESS will be on the order of 500 super-Earths, a type of planet that does not exist in our solar system.
"The number of known planets in the solar neighborhood is growing slowly," Batalha said. "TESS will open that wide."
Because they're so close to us, the stars in the TESS study will be brighter, which will make it easier for future missions like NASA's James Webb Space Telescope to look for signs that planets could be habitable.
This work requires telescopes to study the tiny portion of starlight that passes through the thin atmosphere of a planet (if any) and looks for fingerprints of life-friendly molecules such as free oxygen, methane, and water. Separating these weak signals from the rest of the starlight will be extremely difficult for small, rocky planets with compact atmospheres.
"Not only do they become names in a catalog, but they become goals" I will accept personalities, "Batalha said of these planetary profiles." We will learn so much more about them than we ever did with the Kepler Planets can because they are so close. "
TESS will be prepared to identify the orbiting red dwarfs, the small, gloomy stars, about three quarters of the stars in the sky.
Red dwarfs are so small that their planets appear relatively large, making them easier to discover, and because the stars are so dark, their habitable zones are much more compact, which means that TESS was able to observe multiple transits during each of its 27-day observation periods.
The Space Telescope was also able to study all kinds of other celestial phenomena including supernovae, flare stars, and active galaxies.
"If you have a space mission in the sky, your best bets are usually not the ones you planned, "said MIT astrophysicist Sara Seager, deputy science director of the mission. 19659003] Because of these narrow observation windows, the spaceship will not be able to pick up planets with longer earth orbits than Kepler might. But as the 13 observation strips in each hemisphere overlap at the poles, TESS will look for nearly a year at both the northern and southern polar heavens. In a few years – if TESS's two-year mission is extended long enough – it could find the types of rocky planet in habitable zone that Kepler could.
And TESS could possibly take much longer than Kepler, which is expected to run out of fuel within the next few months.