A screen that will hover in front of NASA's next large telescope could allow a photograph of worlds that may contain life decades before the planned date
Will the future space telescope of the American space agency, NASA, be able to photograph planets similar to Earth? Astronomers have always dreamed of such images that would allow them to explore worlds outside our solar system and look for signs of life, or at least signs of conditions that could allow life. But it always seemed that the technology that would allow this was decades away. But now, an increasing number of experts believe that the wide-field infrared scanning telescope, WFIRST, which NASA is developing, will be able to take pictures of planets similar to ours already in the near future. The agency officially began work on the telescope in February 2016 and plans to launch it in 2025.
When WFIRST is launched it will be equipped with a 2.4 meter diameter mirror that guarantees a panoramic field of view of the sky. He will use this wide eye to study dark energy - the mysterious force responsible for accelerating the expansion of the universe. But another burning issue - the existential quest to know if we are alone in the universe - is already affecting the mission.
Researchers have already discovered more than 3,000 planets around other stars and they expect to find tens of thousands more over the next decade. According to rough statistical calculations, every star in the sky is accompanied by at least one planet, and it is possible that around a fifth of the stars similar to our sun have a rocky planet in an area favorable for the existence of life, an area that is neither too hot nor too cold that allows water to exist in a liquid state. The best way to learn whether such worlds are similar to our Earth is to simply see them. But photographing such planets, from a distance of light years, is a difficult task. Such a planet, which might have life on it, would appear from such a distance as a faint spot almost engulfed in the glare of the bright light of the nearby star ten billion times brighter.
Photographing such dim planets with ground-based telescopes is doubly difficult because Earth's turbulent atmosphere obscures the starlight. Most experts therefore agree that the solution is to use telescopes in space. But NASA's Hubble Space Telescope, as well as its giant successor, James Webb Space Telescope, which should be launched in 2018, lacks the level of contrast necessary for this; They don't even come close to the required level. To help WFIRST obtain images of planets it will be equipped in the coronagraph Advanced for photographing planets - an internal device that will filter the light of the stars using a complex array of masks, mirrors and lenses. But the coronagraph is a late addition to the WFIRST project, and the telescope was not specifically designed to work with it. As a result, experts predict that the coronagraph intended to be installed in the telescope will not be able to achieve the level of contrast suitable for obtaining images of other planets similar to Earth. Taking such images is such a challenging task that NASA's current work plans tend to postpone the idea for another twenty years or so, during which time the agency will develop the technology and gain the budgetary breathing space to build an entirely new space telescope after WFIRST.
A device called "starshade" may shorten the way. The device includes a paper-thin screen, shaped like a sunflower flower and the size of half a football field, that will hover tens of thousands of kilometers directly in front of WFIRST and block the light from the target star the way we can block sunlight in the sky by extending a thumb. Star screens can work with telescopes of any type. By casting a deeper shadow, the star screen could allow WFIRST to see fainter planets than would be visible with the coronagraph. If the star screen and the telescope work together, they will be able to obtain images of about 40 planets, including planets similar in size and orbit to Earth. "If WFIRST has a star screen, and only if it has such a screen, it will be able to give us images of some planets similar to our blue Earth towards the end of the next decade instead of waiting another twenty years," says Jeremy Kasdin, a professor at Princeton University and the chief scientist of the WFIRST Coronagraph Project. "This is a real opportunity to find another Earth sooner, and at a lower cost, before investing a huge fortune in NASA's next giant space telescope."
Although WFIRST will only be launched in about ten years, the decision whether to move forward with preparations to integrate a star screen into the program must be made soon because small adjustments will need to be made to WFIRST to allow it to work in coordination with a screen that will be placed thousands of kilometers away in empty space. In practice, the star screen does not yet exist as an official mission. Paul Hertz, director of the astrophysics division at NASA, says that now the agency is in a situation of "not rejecting a star screen". Meanwhile, not disqualifying is a situation that looks a lot like a concerted effort to build a star screen. When NASA officially announced the start of the WFIRST project, it also confirmed that the telescope would be launched into orbit 1.5 million kilometers from Earth, an area calm enough to allow the operation of a star screen. In addition, the agency recently established a "working group for readiness for a star screen" (SSWG) and officially classified the star screen as a "technology development activity". These moves could speed up the agency's progress in developing the Star Screen.
Kasdin is already working today on an experimental facility in the basement of the large Frick Chemistry Laboratory at Princeton University. It is a tube one meter in diameter and 75 meters long with a camera on one side, a laser on the other, and between them a miniature model of a star screen. He predicts that by the end of the summer of 2016, the experimental facility will show what the contrast ratio is that will allow, when magnified to real dimensions, to photograph planets similar to Earth. Meanwhile, the space technology company Northrop Grumman has tested miniature star screens at the bottom of a dry lake in Nevada and at a giant solar telescope in Arizona, while at NASA's Jet Propulsion Laboratory (JPL) researchers are demonstrating ways to make the delicate petals of a larger-scale star screen, folding the The entire structure to put it in a rocket, place it in space and deploy it there to the dimensions of a baseball field.
Not all obstacles on the way to building a star screen are technological. The cost of a star screen for WFIRST can easily reach a billion dollars - far beyond the limits of the budget allocated to the telescope. Therefore, it must first go through a proposal and approval process as an independent project with its own budget at NASA. This is a serious obstacle in the way of a technology that is only in the initial stages of development. But investing in such a project can yield results of real historical importance: obtaining the first image of a distant and foreign Earth will be a one-time historical event. Should we try to do this as quickly as possible or delay for decades? NASA and the astronomical community must decide soon.
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Animation of the "star screen" layout
