Outside the solar system, there are probably planets that are potentially habitable, but it is impossible to see them from Earth even with the use of modern telescopes. RT spoke with an astronomer, associate professor of the physics department of Moscow State University, senior researcher at the State Astronomical Institute Vladimir Surdin about how extrasolar celestial bodies are investigated and when a person can step on the surface of the Red Planet.
RT: Since the discovery in 1995 of an exoplanet, that is, a planet located outside the solar system, astronomers have discovered more than three thousand such celestial bodies. One of them was registered this summer. What do we know today about exoplanets?
VS: Planets near neighboring stars have been found for more than 20 years, and over the years, quite a lot of different methods have accumulated. Among them, there are two of the most productive, thanks to which 90% of all exoplanets were discovered. It is a radial velocity method and a coating method.
Using the method of radial velocities, they measure the speed of a star moving towards us or away from us by its spectrum. The so-called Doppler effect causes the spectrum to change its shape slightly: spectral lines shift to the blue or red end of the spectrum, depending on whether a star is approaching us or moving away from us.
This can happen for many reasons. For example, the star itself can pulsate - then its surface approaches or recedes. But one can quite accurately figure out when these wiggles of the star are associated with the presence of planets next to it. In this case, periodic changes occur, and by tracing several orbital periods, one can make sure that it is the planet that "shakes" its star. Thus, in 1995, the first exoplanet was discovered, and to date, about 30% of exoplanets have been discovered by this method.
If we accidentally managed to find ourselves in the plane of the planet's orbital motion, we can use the second method. At each revolution around the star, the planet will be projected onto it. That is, we, the inhabitants of the Earth, will see how it passes against the background of the star's disk and slightly covers it. The brightness of the star will decrease very slightly, but you can notice it. The covering method - in translation from English it is called the transit method - made it possible to discover and catalog 50-60% of all planets found in other stars.
All this means that we just guess about their existence. The planets shine faintly, so the telescope cannot detect them. Nevertheless, about 80 exoplanets have already been photographed. This is not much, because 3.5 thousand exoplanets have been discovered. The images of which we managed to obtain are gigantic and, in terms of the search for life, uninteresting. And such small ones as the Earth have not yet even been photographed - we do not know anything about them, except for the very fact of their existence, mass and size. Because of this, the search for life is not being conducted on them, we are waiting for larger telescopes to get their images and spectra. Based on this data, we will be able to find out the composition of the atmosphere of the planets, which may hint at whether there is life there or not.
RT: Is it possible to reliably determine whether there is life on an exoplanet or not?
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VS: Biologists do not know any other options for life, except for the earth, carbon, which lives in an oxygen-rich atmosphere. True, there are some subtypes of living beings: some breathe oxygen, others do not need it. One way or another, there are few options. We assume that if the planet has an atmosphere rich in water vapor (and, as you know, no life forms can do without water), if there is oxygen, carbon dioxide, maybe methane as a waste product, then on the surface be life. If it is hiding under the surface, then our methods cannot detect it there.
RT: What useful knowledge can you gain by studying exoplanets? Do they help to learn something about the Earth?
VS: There is no useless knowledge at all, sooner or later they all find application. 200 years ago no one understood why Faraday was engaged in electricity, and today no one can live half an hour without him. The question of why we need this is rather naive. The human race only manifests itself in that it accumulates knowledge. Therefore, man became the king of nature.
All other living beings are not as inquisitive as a person, and therefore are in a subordinate state. Comparing different planets, we better imagine the past and future of the Earth - its future is especially important to us. Perhaps there is no other application to this knowledge.
RT: Recently, there were reports on the Internet that single-celled life - microbes - was found on Mars. Is this information true?
VS: If such messages have spread, it only speaks of the qualities of their distributors, nothing else. This means that people do not know how to filter information. To disseminate such sensations is obtained at the expense of a poorly educated public, which can be slipped into questionable information.
If a person has a fundamental knowledge of nature, it is not so easy to buy it as a hyped sensation. That is, it is necessary to start with the family and school, with the education of a competent, critically thinking person.
RT: Recently, politicians have been talking about the possibility of colonizing Mars in the 2030s. Do you think this is realistic?
VS: There is no talk of colonization. A colony is a separate settlement that lives at its own expense, with its own resources.
There are no resources on Mars. If a person ever comes there, he will be forced to supply himself from Earth, which is very expensive. Therefore, while we are exploring Mars, it is much more efficient to do it with the hands of robots.
They are reliable, working for decades near Mars and on its surface. A man on this planet cannot yet justify his presence - we would have to spend a lot of resources on his flight, supply, maintenance of life.
In addition, neither Russia, nor America, nor China have the physical ability to do this yet, they do not have sufficiently powerful missiles. They are likely to appear shortly, by 2025-2028. But even they will not be able to deliver a person to Mars alive and well, because the dose of radiation that the astronaut will receive during the flight is very large.
True, Elon Musk (founder of Space X. - RT) announced his plans for a fast flight, which will take two to three months, and in the fall presented a plan for a new version of the rocket. If Musk manages to realize his intentions (and he usually succeeds), then in the conditions of such a flight, a person will be able to reach Mars, retaining his health, and work there for some time. But this is still expensive and unjustified. So far, we are only talking about planetary exploration. When we understand what Mars is, what conditions are there for life, if the planet has its own life, Martian, then it will already be possible to talk about colonization. Perhaps the first man will visit Mars just as he once visited the Moon. But if we talk about colonization, then I think that this time will not come soon - in a century, and maybe more.
RT: Over the past year, have there been any discoveries or developments that have impressed you?
VS: If we talk about the announced projects, then the project of the new Elon Musk rocket is very interesting. In my opinion, it is technically feasible.
Among those already implemented, I will name gravitational-wave detectors, which were the first to record gravitational waves. This happened in September 2015, but a scientific publication appeared in early 2016. Until now, we have been deprived of this channel of information, and in the meantime it turned out to be the most penetrating, all-pervading: there are no obstacles for gravitational waves.
Now we are starting to explore what we could not even dream of before: merging black holes, explosions of neutron stars.
It's hard to imagine what else we will be able to see, but this achievement of the past year has already begun to work.
RT: What objects in space are scientists most interested in right now?
VS: Everyone is interested. It is wrong to ask about scientists in such a context without specifying the area of research. Biologists are interested in nearby objects: the moons of Jupiter, Saturn. Those objects where the potential for finding life under the ice is expected. Astronomers are interested in distant objects, physicists are interested in small ones, so each has its own area of interest.
Anna Odintsova