Recently, the media spread the news: Petersburg astronomers discovered a planet that could contain liquid water, which means life. While newspapers and news agencies were multiplying the sensation, at the Pulkovo Observatory they only sighed: the journalists had mixed everything up.
Not discovered, but calculated, and in this case there can be no talk of any liquid water. Which, however, does not diminish the achievements of our scientists. Ivan Shevchenko, head of the laboratory of dynamics of planets and small bodies at the Pulkovo Observatory, told the reporter about how new planets open and "close".
Ivan Ivanovich, the discovery of Petersburg astronomers excites the imagination by the fact that the new planet revolves around Alpha Centauri, which has always been the object of special attention of science fiction writers …
Ivan Shevchenko: Here you also say the word "discovery", which in principle is incorrect. We have only pre-calculated the exoplanet's orbit in the Alpha Centauri system. It is premature to talk about an astronomical discovery until it is discovered by observers.
Is an exoplanet?
Ivan Shevchenko: A planet outside the solar system. Already 1,822 exoplanets have been discovered, so this in itself is not such an out of the ordinary event. But Alpha Centauri is the closest star to us. This is why our calculations have attracted such attention.
It is worth noting that Alpha Centauri is a double star. In 2012, a team of European astronomers announced the discovery of a planet around one of its components. But this was done on indirect grounds and at the limit of the capabilities of the equipment that they possessed. And now their discovery seems to be not confirmed. So it is possible that the planet we have calculated may be the only one in the Alpha Centauri system.
Promotional video:
What is known about her?
Ivan Shevchenko: It revolves around both components of the binary star, and not one, like the previous one, which I just spoke about. It can be said with sufficient confidence that its orbital period is approximately 700 Earth years, and the distance to the star is 80 astronomical units. I can't speak about the size, but usually such planets are much larger than the Earth in diameter.
I don’t know where the information came from in the media that this exoplanet could have liquid water. It is categorically wrong. She is out of the zone of life. Just imagine - the planet is 80 times farther from Alpha Centauri than the Earth is from the Sun. It is very far away, the level of stellar study falling on its surface is too low. It is possible that there may be ice, but not liquid water.
It is dark, cold and the year lasts 700 years … But at least a cheerful name can you give it?
Ivan Shevchenko: Hardly. The fact is that the assignment of names to planets is strictly standardized. As a rule, this is a derivative of the name of either the parent star, or the spacecraft from which the observations were carried out, or the project, within the framework of the discovery. The planet we have calculated, if confirmed, will be called Alpha Centauri ABb, since it revolves around both components - A and B.
Theoretically, you can declare your desire to give the new planet the name of your best friend or beloved woman. But it will still not be accepted in world science.
It's like with asteroids. About 700 thousand of them are now open - it would seem that there is where to roam. Moreover, they are often given real names. So, at one time, a significant part of the asteroids was discovered at the Crimean Observatory, and many of them were assigned names of Soviet origin. But the procedure is such that the name of the new celestial body must be justified, it is discussed and approved by the commission of the International Astronomical Union. You can name an asteroid your cat only if you can convince scientists that she made a great contribution to astronomy.
I understand that this is difficult, but maybe you can try to explain how exactly exoplanets are calculated?
Ivan Shevchenko: Of almost two thousand known exoplanets, only a few have been discovered by direct observations. The rest are opened by indirect methods. There are many of them, but two main ones can be distinguished. The first is the radial velocity method, when the oscillations of the parent star are studied due to the gravitational influence of the planet. The second is the method of transits, that is, observing the passage of planets across the disk of a star. Back in the 18th century, the navigator Cook observed the transit of Venus across the Sun in a similar way.
As for "our" planet, we used a completely new method developed by scientists at the Pulkovo Observatory. It is based on the analysis of resonant chaotic dynamics in the zone of a binary star. It's not clear, right?.. In general, everything suggests that this planet exists, and we can predict its location with a fairly high degree of certainty.
Although anything can happen. There is such a concept as "the level of likelihood of the discovery of a given planet." The same Europeans, who discovered the planet in the Alpha Centauri system, announced that the probability of a false alarm is one thousandth. And you see - this thousandth worked. The existence of the planet is not confirmed.
Be that as it may, now it's up to the observers.
How many exoplanets have been discovered by scientists at the Pulkovo Observatory?
Ivan Shevchenko: I will probably disappoint you. Russian scientists have not yet discovered a single exoplanet at all. It is possible to predict, but confirmation requires very powerful modern instruments such as NASA's Kepler astronomical satellite. It is with its help that the main part of exoplanets is now being discovered. But this is the highest technology and billions of dollars. Observations can be made from the ground using the radial velocity method, but for this, again, one cannot do without ultra-precise spectrographs, which are not available either at Pulkovo or any other Russian observatory.
However, astronomy has no geographic boundaries. And if the planet we have calculated attracts the attention of the scientific community, perhaps an international program will be created to discover it, then the team of researchers will certainly include St. Petersburg scientists.
We do not open planets, but we “close” them. There is such an interesting planetary system Gliese-581 in the constellation Libra, consisting of planets orbiting a single star. One of the first exoplanets to enter the life zone was discovered here. But a young employee of the Pulkovo Observatory, Roman Baluev, using advanced data processing methods developed by him, proved that in fact there is no such planet. Its findings are globally recognized.
It must be said that the "closure" of the planets is not such a rare phenomenon in astronomy. Remember at least Pluto. As you know, in 2006 it was removed from the list of planets. I took part in the General Assembly of the International Astronomical Union in Prague, where this decision was made, and I think it is completely fair. The discussions were serious. The Americans especially objected - Pluto was discovered in 1930 by their compatriot Clyde Tombaugh.
But something had to be done, because in the Kuiper belt, planets like Pluto began to be discovered, and even larger. There were two options left: either to increase the number of planets in the solar system, or to introduce a new classification. So we were left with eight planets. And Pluto and a number of other celestial ones entered a new class of dwarf planets.
What is the closest planet to us in the life zone?
Ivan Shevchenko: Apparently, this was the planet from the Gliese-581 system, which we “closed”. What after it - I find it difficult to say. Moreover, this data is uncertain - the opinions of astronomers on each object differ.
The life zone itself is not wide. In the solar system, for example, only the Earth is included. Maybe once upon a time Mars also entered, but everything is changing.
Remember that a good location alone is not enough for life to emerge. There must be an atmosphere and many other factors. In addition, first of all, large planets such as our Jupiter or Saturn are discovered. Whether life can in principle exist on such gas giants is a big question. It is generally believed that this is possible only on rocky planets - like the Earth. On the other hand, the giants have rocky satellites that can contain liquid water. What is an indispensable condition for the existence of life in the form in which we know it.
This year, scientists announced that they have found the exoplanet Kepler-186f, which can be called Earth's cousin. Sister - because it is similar to our planet both in rock type, and in size (with an error within ten percent), and in what is in the zone of life. Cousin, not native - because it is not a yellow dwarf, like the Sun, but a red dwarf - the star Kepler-186, located in the constellation Cygnus, at a distance of 500 light years from us.
This star is half the size of the Sun, and the level of its light radiation is 25 times lower. Therefore, the circumstellar zone of life is much more compact. Its outer border is only 0.4 astronomical units (this is the radius of the orbit of Mercury). Accordingly, the year on the "cousin" is three times less - 130 Earth days. The spectral composition of the radiation that falls on this planet is also completely different. This means that completely different chemical and biological processes are taking place. We are left to wonder what kind of life there can be, whether it is similar to ours, what color the plants are …
In general, if we talk about the discovery of exoplanets, then we are now living in an era of discovery, which can be compared with the great geographical expeditions of the 15th - 16th centuries. There is no doubt that over time - perhaps very soon - there will be both "siblings" and "twins" of the Earth in the Universe.
Is it possible to remotely determine if there is liquid water on other planets?
Ivan Shevchenko: With a certain degree of convention. These are things that are on the verge of the possibility of modern technology. With the help of powerful telescopes and special methods, it is possible to observe the lines of chemical elements in the atmospheres of stars as the planets pass through their disk and draw conclusions on this basis. But this is all pretty unreliable. We can assume (I emphasize - assume!) The presence of water in the liquid phase only by the size of the orbit and by the type of star around which the planet revolves.
It turns out that we will never know for certain whether there is life on those planets that enter the life zone?
Ivan Shevchenko: Well, you know, there are theories of different levels of reliability. Let's say, the theory about black holes, which is fundamentally impossible to observe. But, nevertheless, astronomers are confident of their presence by the powerful energy processes that are observed in their vicinity.
Astronomy generally at distances beyond the size of our solar system assumes the absence of any experiment. Only observations and their interpretation based on existing theories …
Ivan Ivanovich, tell me bluntly - is there extraterrestrial life or not?
Ivan Shevchenko: In principle, there should be. It is another matter whether it reaches a reasonable stage, how long this stage lasts, whether civilization goes beyond its planetary system.
Personally, I think that the shaping of life is a natural process. On our planet, it arose almost "immediately" after the formation of the solar system and after that it existed for billions of years, evolved, developed into an intelligent form. The very fact of this, it seems to me, indicates that this is a fairly common phenomenon. It is sufficient that suitable physical conditions are reproduced.
There is an interesting concept of the habitable zone of our Galaxy, formulated by Australian scientist Charles Lineweaver. According to his conclusions, such an annular strip stretches around the center of the Galaxy, where one can assume the presence of complex life forms. At the same time, the peak of the formation of systems suitable for this passed about a billion years before the emergence of the Sun and the planets revolving around it. This means that the inhabited earth is a residual phenomenon. If we have "extraterrestrial brothers", then they must be older than earthlings by a billion years.
Taking into account the fact that on Earth an intelligent form of life has existed for only tens of thousands of years, our Galaxy should now be inhabited by civilizations with a very high level of development. Or they were, but have already disappeared. After all, we do not observe any brothers in reason - neither by activity in radio bands, nor by other indirect signs.
That is, you relate to stories about UFOs and aliens …
Ivan Shevchenko: Skeptical
