(ORDO NEWS) — Since the discovery of the first exoplanet in 1992, astronomers have discovered more than 5,000 planets orbiting other stars. But when astronomers discover a new exoplanet, we don’t learn much about it: We know it exists and some of its features, but the rest remains a mystery.
To get around the physical limitations of telescopes, astrophysicists at Stanford University are working on a new conceptual imaging technique that will be 1,000 times more accurate than the strongest imaging technology currently in use.
Using the gravitational curvature of space-time, called lensing, scientists can manipulate this phenomenon to create images far more advanced than anything that exists today.
In a paper published May 2 in the Astrophysical Journal, the researchers describe a way to manipulate solar gravitational lensing to view planets outside our solar system.
By positioning the telescope, the Sun, and the exoplanet in line with the Sun at its center, scientists can use the Sun’s gravitational field to magnify the light from the exoplanet as it passes by.
Unlike a magnifying glass, which has a curved surface that bends light, a gravitational lens has a curved space-time that allows images of distant objects to be captured.
“We want to take pictures of planets orbiting other stars that are as good as the planets in our solar system,” said Bruce McIntosh, professor of physics at the Stanford School of Arts and Sciences and associate director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC).
With this technology, we hope to take a picture of a planet 100 light-years away that will have the same impact as the Apollo 8 picture of Earth.” The
catch is that the technology they propose will require better space travel, than those currently available.However, the promise of this concept and what it can reveal about other planets makes it worthy of further consideration and development, the researchers say.
Benefits of Light
Bending Gravitational lensing was not observed experimentally until 1919 during a solar eclipse. Because the moon blocked light from the sun, scientists were able to see stars near the sun that were displaced from their known positions.
This was undeniable proof that gravity could bend light, and the first observational proof that Einstein’s theory of relativity was correct. Later, in 1979, von Eschlemann, a professor at Stanford, published a detailed account of how astronomers and spacecraft could use the solar gravitational lens.
(Meanwhile, astronomers, including many at the Stanford KIPAC Institute, now regularly use the powerful gravity of the most massive galaxies to study the early evolution of the universe.)
But it wasn’t until 2020 that imaging techniques were studied in detail for planetary observation. Slava Turyshev of the California Institute of Technology’s Jet Propulsion Laboratory has described a method in which a space telescope can use rockets to scan around light rays from a planet to reconstruct a clear picture, but the method would require a lot of fuel and time.
Based on Turyshev’s work, Alexander Madurovich, a KIPAC PhD student, has invented a new method to reconstruct the planet’s surface from a single image taken directly on the Sun.
By capturing a ring of light around the Sun formed by an exoplanet, an algorithm developed by Madurovic can distort the light from the ring, changing the curve from a gravitational lens, which turns the ring back into a round planet.
Madurovich demonstrated his work using images of the rotating Earth taken by the DSCOVR satellite, which sits between the Earth and the Sun.
He then used a computer model to see what the Earth would look like through the warping effect of solar gravity. By applying his algorithm to the observations, Madurovich was able to reconstruct images of the Earth and prove the correctness of his calculations.
In order to image an exoplanet through the Sun’s gravitational lens, a telescope would have to be located at least 14 times farther from the Sun than Pluto, beyond the edge of our solar system, and farther away than humans have ever sent spacecraft. But that distance is a tiny fraction of light years between the Sun and the exoplanet.
“By bending the light that is bent by the Sun, you can create an image far beyond the capabilities of a conventional telescope,” said Madurovic. “Thus, the scientific potential is an untapped mystery, because it opens up new possibilities for observations that do not yet exist.”
Beyond the Solar System
At present, to image an exoplanet at the resolution scientists describe, we would need a telescope 20 times wider than Earth.
By using the Sun’s gravity as a telescope, scientists can use it as a massive natural lens. A Hubble-sized telescope combined with a solar gravitational lens would be enough to image exoplanets with enough power to capture fine detail on the surface.
“The solar gravitational lens opens up a whole new window of observation,” says Madurovich. “This will allow us to explore the detailed dynamics of planetary atmospheres, as well as cloud distribution and surface features that we are not able to explore now.”
Madurovic and McIntosh say it will take at least 50 years before the technology is introduced, and likely more. To implement it, we will need faster spacecraft, because with current technology, the journey to the lens can take 100 years.
When using solar sails or the Sun as a gravitational slingshot, this time can be 20 or 40 years. Despite the uncertain timing, McIntosh says he is driven by the possibility of seeing if some exoplanets have continents or oceans. The presence of any of these is a strong indication that life could exist on a distant planet.
“This is one of the last steps in figuring out whether there is life on other planets,” McIntosh said. “When you take a picture of another planet, you can look at it and maybe see green spots that are forests and blue spots that are oceans – it would be hard to say that there is no life on it.”
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