MOSCOW, 30 March. /TASS /. Physicists of the Moscow Institute of Physics and Technology (MIPT) and the Space Research Institute of the Russian Academy of Sciences have developed optical technology for the "correction" of light coming from distant stars, which will significantly improve the work of telescopes and will enable us to directly observe exoplanets as Earth-twins, MIPT said in a press release.
"Through the use of a relatively simple optical set-up, we can obtain the image contrast at the quality necessary for the direct observation of Earth-type planets by means of coronagraphs. Of course, compared to foreign developments, our system requires a more complex control technique, but at the same time it is much less dependent on the temperature stability that greatly simplifies its operation in space," said Alexander Tavrov, team leader and an associate professor at MIPT and the head of the Planetary Astronomy Laboratory at the Space Research Institute of the Russian Academy of Sciences.
Difficulties in searching for exoplanets
Over 2000 exoplanets have been discovered since 1988. The faint light of these planets is almost impossible to see without special tools - it is "overshadowed" by the radiation of parent star. Therefore exoplanets are discovered by indirect methods: by registration of the weak periodic fluctuations in the luminosity of the star when a planet passes in front of its disk (the transit method), or by spectral translational vibrations of the star itself from the impact of the planet’s gravity (the radial-velocity method). Astronomers were able to directly obtain images of exoplanets in the late 2000a.
To obtain them, the scientists use stellar coronagraphs first created in 1930s for observations of the solar corona outside eclipses known as solar coronagraphs. These devices have a focal mask - an "artificial moon" inside them, which blocks some part of the field of view - ultimately, it covers the solar disk, allowing you to see the dim solar corona. To repeat this technique for the stars, we need a much higher level of accuracy and much higher resolution of the telescope, which accommodates a coronagraph. Apparent size of the orbit of Earth-type planets, nearest to us, is about 0.1 arcseconds. This is close to the resolution limit of modern space telescopes (for example, the resolution of the space telescope Hubble is about 0.05 seconds).
Optical scheme of the experiment
Scientists have found a way to obtain the highest resolution, while using relatively simple and inexpensive systems of adaptive optics. They used the idea of a EUI (Extremely Unbalanced Interferometer) proposed by one of the article’s authors - Juno Nishikawa, a Japanese scientist working at the National Astronomical Observatory of Japan.
The EUI light is divided into two beams (weak and strong), whose amplitudes have an approximate preset ratio of 1:10. A weak beam passes through the adaptive optics system, after which the two beams are brought together again and interfere with each other. As a result, the weak beam "smooths out" the light of the strong beam, which can significantly reduce both the distortion of the wavefront.
With the help of computer simulation, they have determined approximate characteristics of the system developed by them. In the future, scientists plan to create a laboratory prototype and perform a number of experiments on it.
The paper was published in the Journal of Astronomical Telescopes, Instruments, and Systems (JATIS).