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NASA's TESS satellite will boost the search for Earth-like worlds nearby

On Monday, April 16, the Transiting Exoplanet Survey Satellite (TESS) will be launched from the Cape Canaveral Air Force Station in Florida. NASA's new exoplanet hunter will train his sights on stars closer and brighter than his predecessors. If TESS is up to the scientists' predictions, it could energize our search for life in the cosmos.

When the Kepler space telescope was launched in 2009, scientists did not know what fraction of the stars harbored the planets. The Kepler mission was a statistical exploration that seeks to see how often planets occur around stars, Harvard astronomer David Latham told Space.com. "One of Kepler's big surprises was finding this entire population of planets with sizes between Neptune and Earth, and there is none in our solar system, zero, and they are everywhere," Latham said. who worked on the Kepler project for almost 20 years.

"Kepler is what made us aware that planets are as common as telephone poles," SETI Institute astronomer Seth Shostak told Space.com. "But the stars that Kepler was watching for four years … were between 500 and 1,500 light -years away." TESS will inspect the local neighborhood for planets like Earth. [NASA’s TESS Exoplanet-Hunter in Pictures]

  Illustration of an artist from NASA's Transiting Exoplanet Survey Satellite, which will search for small planets around nearby stars.

An artist illustration of NASA's Transiting Exoplanet Survey Satellite, which will search for small planets around nearby stars.

: NASA's Goddard Space Flight Center

TESS is designed to find planets orbiting stars scattered across the sky, astrophysicist and pioneering exoplanet researcher Sara Seager told the Space.com Institute Massachusetts technology. The satellite is not specifically designed to look for planets that can support life, but it can find planets orbiting the habitable zone of small stars, said Seager, who serves as deputy scientific director of TESS.

TESS will find signals from planetary candidates, Seager said. It will take a lot of follow-up work to determine if these candidates are truly planets, rather than binary stars, artifacts in the data or something else. Once this is accomplished, you can begin a deeper investigation. Unlike Kepler, the stars that TESS examines will be bright enough and close enough to allow detailed tracking studies with large ground-based telescopes, the Hubble Space Telescope and the upcoming James Webb Space Telescope.

The amount of starlight that a planet blocks astronomers the size of the world, while the frequency with which the planet passes in front of its star indicates the orbital period of the world, said Shostak. Scientists can determine the mass of the planet using the Doppler effect to measure the wobble that the planet induces in its star. And mass divided by size is equal to density, so astronomers can determine if they look at a swollen ball of gas or a piece of solid rock. In addition, these planets are close enough so that other telescopes can look inside their atmospheres. When a planet transits its star, part of the light from the stars passes through the planet's atmosphere before reaching Earth. Different gases absorb different wavelengths of light, and scientists can determine the composition of the planet's atmosphere by analyzing the spectrum of this light using more powerful observatories. [7 Ways to Discover Alien Planets]

  Astronomers can study the light of the stars that filters through atmospheres of exoplanets, looking for signatures of molecules that can be signs of life.

Astronomers can study the starlight that filters through exoplanet atmospheres, looking for signatures of molecules that may be signs of life.

Credit: NASA, ESA and A. Feild (STScI)

"Twenty years ago, if you told me that we are going to do this kind of spectroscopy of planet atmospheres around other stars, I would have said you are crazy", said Latham. "Now we're doing it."

Scientists are looking for life signatures, byproducts that organisms could emit into the atmosphere. "The first thing is that we are looking for water vapor," said Seager, "because all life, as we know it, needs liquid water, and water vapor is a sign of surface water."

"After water, oxygen would be fantastic, oxygen is our best biofirm gas on Earth," said Seager, so we're looking for what we know. "After that, we have many gases in which we are interested, but above all in space we look for gases that do not belong, that are there in large quantities, enough to really be detected from very far away." [The Drake Equation Revisited: Interview with Planet Hunter Sara Seager]

Many products of biology can also come from geology. For example, if scientists see methane along with many other hydrogen-rich gases, the source is probably not biological, Seager said. However, finding methane along with oxygen would be promising, because these gases would react with each other and turn into something else if they did not occur continuously, he said. Unfortunately, it is often impossible to completely discard one source over the other.

On the other hand, scientists can overlook the signs of life that are radically different from us. "He's a bit like the drunkard looking for his keys: look under the lamppost, because that's where he can see them," Latham said. "We look for a life similar to ours, because we believe that we understand the organic chemistry involved and that is why we believe we know how to interpret it [evidence for it]"

  Future telescopes such as NASA's James Webb Space Telescope (on the right) will follow up to the discoveries of TESS exoplanets to verify if the newly discovered planets have atmospheres that could support life.

Future telescopes such as NASA's James Webb Space Telescope (on the right) will track discoveries of TESS exoplanets to see if the newly discovered planets have atmospheres that could support life.

Credit: J. Krissansen-Totton

The search for intelligent life is guided by the Drake equation, a formula devised by the astronomer Frank Drake to estimate the probability of receiving signals from intelligent civilizations. The terms of the equation begin with the number of stars in our galaxy and proceed to the number of civilizations that actively transmit their presence in space. Kepler mostly reaffirmed the fraction of stars that have planets. The TESS mission will enrich our understanding of how many planets life could support, and even the fraction of those planets where life can really happen, explained Seager, further limiting the equation.

"Thirty years ago, if you ask [ed] people," Do you think there are many planets out there? "Most people who knew something about astronomy would say," Yes, they probably do. " But nobody knew, "said Shostak. With Kepler, the researchers discovered that the universe is full of planets. "For the first time in 300,000 years, Homo sapiens had found planets around other stars," he said.

Soon after, scientists began to obtain enough data to hypothesize that many of these planets could be habitable. . During the last quarter of a century, science has increasingly led scientists to believe that the existence of life may not be a miracle after all, Shostak said. And he said he sees no evidence that this trend is coming to a halt.

TESS will open the way for a large number of discoveries and deepen our understanding of many phenomena in the cosmos. "There are technical astrophysical questions that will interest many scientists in the community," Latham said, "but I think the question that is going to get the attention of the educated public is this: are we alone?" [19659002] Visit Space.com on Monday, April 16 for full coverage of the launch of NASA's TESS mission. A live webcast at the launch begins at 6 p.m. EDT (2200 GMT).

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