The search for an extra-terrestrial life requires a new space telescope, according to astronomers

If NASA really wants to become serious in the search for life out of the Earth, scientists say that the space agency should launch a new large telescope in space, able to directly capture the images of planets outside our system solar. Such technology does not exist fully for the moment. But astronomers say it's our best bet to find another Earth, an Earth that could harbor biological organisms.

This mission concept is the first recommendation of a new report written by members of the National Academies of Science, Engineering and Medicine. Congress instructed the academy to find the best strategy to study and explore the exoplanets, worlds outside the solar system. And after gathering expert feedback in the field, National Academies made seven recommendations, with the telescope at the top of the list.

This is an ambitious demand, given the harsh realities that NASA had to face in trying to build its next big space observatory, the James Webb Space Telescope, or JWST. Its initial goal was to cost $ 1 billion and launch in 2007. Last June, NASA acknowledged that the entire project would cost $ 9.66 billion and that the telescope would not be launched until 2021 at the earliest. And the type of telescope recommended by this report would require new technologies that have not yet been tested in space, which could make the vehicle even more complex and costly than JWST.

However, when creating this report, the authors did not think about the potential financial constraints. Scott Gaudi, professor of astronomy at Ohio State University, author of the report and who is also working on the mission concept for a space telescope called HabEx, recounts: The edge. "It's just a consensus on what the exoplanet community believes are the most important things to do to meet the scientific goals we have."

The NASA

These goals are relatively simple. The first agenda of the report stresses that we must understand how planets are formed. When stars are born, they typically form surrounded by a swirling disc of gas and dust, and then the individual planets merge within these discs. So, how do these discs go from simple gas to full-fledged planets?

The second goal is the one everyone wants to discover on Earth: are there other Earth-like planets that could accommodate life? And that's why the new telescope could be so important. Taking direct pictures of planets could tell us a lot about what they look like and about their atmosphere. The gas that surrounds a planet can contain important clues to what is on the surface. For example, gases associated with life, such as oxygen and methane, would be a great sign that biological organisms are present in a distant world. "We could get a census of the atmospheric composition of a large sample of Earth-like planets," says Laura Kreidberg. The edge.

Nowadays, astronomers find mostly exoplanets thanks to intelligent but indirect methods. Perhaps the most common way of looking at distant worlds is to look past their parent stars – what is called a transit. These crossings slightly block the starlight, causing a slight drop in brightness that can be measured from the Earth. NASA's TESS satellite, already in orbit around the Earth, searches for planets this way, as does the future James Webb Space Telescope. Another method is to observe how the gravity of a planet affects its host star. Even if they are small, the planets can swing their stars slightly, a sign of their presence.

The direct imaging of an exoplanet is however a monumental task, especially that of the size of the Earth. These planets are very close to their parent stars and are drowned under the starlight. For example, a distant planet, potentially similar to Earth, is about 10 billion times weaker than the one it runs on. Thus, in order to directly imagine these planets, scientists will have to equip future space telescopes with special tools that block or reduce the light of a star.

Image: NASA

Fortunately, astronomers have worked on that. A concept is known as a coronagraph, an optical instrument that can be attached to telescopes to remove light from a star with mirrors, making it easier to see planets that are hiding nearby. Telescopes on Earth and in space have been equipped with coronographs to help study the Sun, but a high-contrast instrument to block the light of distant stars has not yet been fully tested in space. NASA is currently planning to demonstrate this technology for the first time on one of its upcoming space telescopes, WFIRST – a move that National Academies strongly recommend.

But there is another option besides the coronograph. Astronomers are eager to try something called a star. It is a large flower-shaped structure that would fly off the telescope, blocking the light of a star by projecting a shadow. "No light from the stars is in your telescope, but the light of the planet is entering your telescope," says Gaudi.

The problem, however, is that this technology is quite complicated. A starry sky should fly about 100,000 kilometers from a telescope in the space – very precisely – to properly block the light of a distant star. And as the coronograph, the starshade is not yet a completely mature technology. In addition, many of the telescopes proposed that astronomers would like to build to directly image the exoplanets would be huge and heavy. For example, a concept currently being studied, called LUVOIR, would have a much larger mirror than that of JWST.

Any direct imaging telescope project will cost billions of dollars to launch, which can be hard for Congress to swallow, especially given the delays and cost overruns of JWST. Meanwhile, the Trump administration has already proposed to cancel the WFIRST telescope, which would test the coronograph technology, citing project cost overruns. But exoplanet astronomers say they are optimistic that a big project of this nature could happen someday. "I think it's an ambitious but achievable goal compared to what we've already done, like landing the first man on the moon," says Kreidberg. "It's something that's within our reach."

Gaudi also understands the challenges involved in getting something like this. But the report was simply meant to reflect what the exoplanet community hopes to achieve. Soon, scientists will come together to prioritize the types of missions NASA should fund, as part of a larger effort known as a ten-year survey. This report will examine the financial realities when recommending which missions to pursue.

But Gaudi hopes that lawmakers can see the importance of such an ambitious mission. "These missions are not incompatible with our fiscal capabilities," he says. "It's just something we have to choose to do. We think the time has come to go and do it now and we could have the answer to this very profound question of the next generation. "