Future gravity telescope – how to see exoplanets? | Urania

Futuristic technology developed by scientists at Stanford is expected to enable a whole new class of astronomical imaging – far more advanced and precise than ever before.

Since the discovery of the first exoplanet by Professor Wolszczan (in 1992!), scientists have already identified more than 5,000 globes orbiting other stars. However, usually when astronomers detect a new exoplanet, we don’t really learn much about it. We know then (and at best) that such a planet exists, we know some of its characteristic features, but the rest remains a mystery. The other planets are just too far away and too small to capture clearly, just like the planets in our system.

To circumvent these physical limitations of telescopes, astrophysicists at Stanford University have developed a new imaging technique that, if successfully implemented, would be about 1,000 times more sensitive than the best methods currently in use. Using the well-known gravitational lensing, i.e. the effect of space-time distortion by strong gravitational fields, we could skillfully manipulate this phenomenon in order to obtain much more accurate images of objects. distant.

The gravitational lens was confirmed experimentally in 1919 during the solar eclipse. When the moon temporarily obscured the solar disk, scientists were able to see stars close to the sun, but this time slightly offset from their well-known positions in the sky. When we observe the stars at night, they are naturally far from the sun, and therefore its strong gravity does not bend their light relative to the terrestrial observer. Solar eclipses are therefore a unique opportunity to perceive and measure such changes. In 1919, it was unequivocal proof that gravity can bend light, but also the first observational proof of relativity.

Later in 1979, Professor Von Eshleman published a detailed description of how astronomers and spacecraft can practice gravitational lensing of the Sun. However, it was only after almost a hundred years, in 2020, that this imaging technique was well studied for possible observations of distant planets. Slava Turyshev from the California Institute of Technology presented a method in which a space telescope could recreate a clear image of a distant exoplanet. However, it was already known then that this required a lot of rocket fuel and … time.

Now, in new work published in The Astrophysical Journal, Stanford scientists describe their own way of using the Sun’s gravitational lens to peek at planets outside the solar system. By aligning the telescope, the Sun and the exoplanet with the Sun at the center, it is theoretically possible to use the Sun’s gravitational field to magnify the image of such an exoplanet many times over. So, like a magnifying glass whose curved surface deflects light rays, a gravitational lens would strongly bend space-time, allowing precise images of distant planets.

The goal is to obtain images of exoplanets with the quality of photographs of the planets of our system. The team hopes the new technology can, for example, take a clear “image” of a planet about 100 light-years away. According to the authors of the study, it would be more or less as clear as a photo of the Earth taken by the Apollo 8 mission.

Earthrise – An image of the Earth emerging from behind the moon’s horizon taken on December 24, 1968 during the Apollo 8 mission. Source: NASA/Bill Anders

Based on Turyshev’s work, lead author Alexander Madurowicz of Stanford University developed a method to reconstruct a planet’s surface from a single image taken by looking directly at it when it is behind the sun. After capturing the characteristic ring of light around the Sun, formed by this distant exoplanet, the algorithm developed by Madurowicz would be able to recreate the original light that made up such a ring by numerically reversing the phenomenon of light deflection in the lens. gravitational. In other words, the algorithm transforms the ring back into a circular disc of the planet.

Madurowicz has already demonstrated its work in practice, using photos of Earth taken by the DSCOVR satellite, which is located quite close to us, between Earth and the Sun. His computer model allowed him to see what the Earth would look like if observed as a distortion caused by the Sun’s gravity. Using his algorithm, he was able to recreate the real image of the Earth and thus prove that his calculations were correct.

Problem? It is based on the fact that the proposed technique requires more extensive space travel than we currently have. To capture an image of an exoplanet generated by a solar gravitational lens, a suitable telescope would need to be positioned at least 14 times farther from the Sun than Pluto, and thus beyond the edge of the solar system. That’s far further than any man-made spacecraft ever reached. However, this distance is still a small fraction of light years between the Sun and the nearest exoplanets.

And the image thus obtained would go far beyond the capabilities of an ordinary optical telescope – and even the most advanced. The gravity telescope opens up completely new observation possibilities and a new window on the Universe. Today, to image an exoplanet with such high resolution would require an optical telescope 20 times the diameter of the Earth itself. However, by using the Sun’s gravity as a telescope, you can use it as a huge natural lens. A telescope with the parameters of the Hubble telescope, in conjunction with this solar gravitational lens, would make it possible to take pictures of many exoplanets with sufficient sensitivity to capture fine details on their surfaces – including the dynamics of their atmospheres, the distribution of clouds and other features that we currently have no way to investigate. .

According to Madurowicz and the publication’s second author, Bruce Macintosh, the possible implementation of the new technology will take at least 50 years. For its implementation, faster spacecraft will be needed, because with current possibilities, the trip of the telescope to the right place can take up to 100 years. By using sails or the sun as a gravitational slingshot, this time could be reduced to around 30 years. It’s still a long time, but according to the authors, being able to see whether certain exoplanets have continents or oceans is simply worth it.

– This is one of the last steps to find out if there may be life on other planets – concludes Macintosh. – With this image of the planets you can see green spots which are forests and blue spots which are oceans.

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Source: news.stanford.edu

Prepared by: Elżbieta Kuligowska

Pictured: Diagram showing an imaging method that uses the Sun’s gravitational field to enhance the light of an exoplanet. This would allow a very thorough reconstruction of its appearance. Source: Alexander Madurowicz

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