Many astronomers have long been fascinated by the idea of using the gravitational lens created by the Sun as a telescope. This will allow obtaining direct images of exoplanets with detail not available with any other telescope. However, a recent study shows that such a telescope may be not as effective as previously thought.
A telescope called the Sun
One of the consequences of the theory of relativity is that the gravity of any massive object like a lens is able to change the direction of propagation of electromagnetic radiation and amplify it. Astronomers use it extensively in their work. The gravitational lenses produced by galaxies and galaxy clusters make it possible to study extremely dim objects at the edge of the Universe. And the micro lensing effect created by stellar mass objects makes it possible to find exoplanets in our galaxy.
Our Sun also creates a gravitational lens. And many scientists have long been attracted by the idea of using it to search for extraterrestrial civilizations. Calculations show that if you place a telescope with a mirror like the Hubble in line with the exoplanet and our star in between, the Sun’s gravity will act as a giant lens and amplify its light by many orders of magnitude. In theory, such a telescope would be able to take images with a resolution of up to 10 kilometers per pixel. It will be enough not only to distinguish the outlines of the continents, but also to see the largest man-made structures on the surface and see the night lights of cities.
Until recently, distance was considered to be the main problem with this project. To take advantage of the gravitational lensing effect, the telescope needs to be brought to a distance of 650 a.u. from the Sun. That’s about four times more than the Voyager 1 spacecraft flew over its nearly half-century journey. Obviously, such a mission would require fundamentally different thrust systems than traditional chemical-fueled engines.
Problems of the gravitational-solar telescope
However, this is far from the only problem. A new paper by independent researcher Victor Toth, published on the arXiv preprint server, points to a number of other difficulties that could prevent such a project from being realized and that have not previously been considered by other scientists. One of them is the radiance emanating from the sun’s corona. t is a powerful source of “noise” that makes it extremely difficult to cut off the very dim light coming from the exoplanet.
Another problem is working with the quadrupole moment of the Sun. It determines how much its real shape differs from the ideal sphere. Even a small deviation can cause huge changes in where light from an exoplanet hits.
In addition to these problems, Toth also studied another variable: cloud cover. Since Earth contains moving clouds, we can assume that other planets where life exists also have them. The problem is that clouds make it extremely difficult to separate the signal of the planet’s surface from the “noise” they introduce.
Toth modeled the effects that moving clouds on Earth would cause if it were observed with a gravitational telescope near another star. It is very difficult to distinguish even the familiar structure of the continents in the images, not to mention what could be identified as a biosignature or something made by an intelligent civilization.
A potential solution to the problem is to use a network of 10,000 vehicles, each equipped with a meter mirror. Their simultaneous observations will eliminate noise from clouds and level out the effects created by the Sun’s non-ideal shape and corona. Unfortunately, sending such a huge space fleet of vehicles to such a far distance is currently well beyond the capabilities of our civilization. So, it may be a very long time before scientists are able to take advantage of the gravitational lens created by the Sun.
According to Phys.org
