A stray planet

By Boris Pavlishev: Some time ago, scientists discovered that there are planets that do not rotate around any star, like the Earth rotates around the Sun, but “travel” in the universe all alone. Till now, scientists have discovered only less than 10 such planets, but recently, astronomers in Hawaii noticed a hardly visible blue point which they believe to be another such planet. Later, the object was more thoroughly examined with the help of a more powerful telescope in Chili. Scientists suppose that this is probably the closest free-floating celestial body to us – the distance between it and the Earth is only 100 light years, which is not far from the point of view of cosmic distances. If this planet was formed in a star system, why has it left it? “Well, this happens sometimes,” Russian astronomer Vladimir Surdin says. “If there are several massive planets in a star system, their gravitation fields “come into conflict”, and a larger one may repel a smaller one from the star system. In the Solar System, the largest planet is Jupiter, and the second largest one is Saturn. The others are much smaller in comparison to them. Thus, their gravitation fields do not come into conflict. But if there were two or more planets like Jupiter in the Solar System, one of them may have repelled the others.” “There are probably many “stray” planets in the universe,” Mr. Surdin continues, “but it is rather hard for us to discover them. The reason is that if a planet is near a star, it is lighted, but a stray planet practically cannot be seen. This is why scientists started to discover them only recently, with the invention of infra-red telescopes.” The recently discovered object looks like a small blue point on the photographs. The blue color speaks of the fact that the object has an atmosphere rich with methane, scientists say. Scientists are not sure whether this newly discovered object is a planet or a so-called “brown dwarf” (a species of a small star that has nearly died out). Russian astronomer Oleg Malkov says: “The main parameter by which we may determine whether this object is a planet or a star is by its mass. If its mass is higher than a certain figure, it is a star, if lower, it is a planet. However, the only way we can estimate the mass of a faraway celestial body is by its interaction with another body. But insofar as this newly discovered object is not located in any proximity with another celestial body, it doesn’t interact with any, and we cannot estimate its mass. Still, I believe that most probably, this new object is a planet, not a star.” However, scientists did make some approximate estimates of the mass of the object in question - and, according to them, its mass is 4 to 7 times larger than that of Jupiter. If the body were at least 13 times larger than Jupiter, according to physical laws, its nucleus would have been so pressed by the body’s own weight that a thermonuclear reaction would have begun within it, and the body would have become so hot that it would have been a star, not a planet. The temperature of the new object’s surface is estimated as +430° Celsius, which is typical of a planet, not a star. Astronomers believe that most likely, the object formed not earlier than 120 mln years ago in the constellation called Dorado, or The Golden Fish. “Some “stray planets” may even be inhabited by primitive forms of life,” Vladimir Surdin says, “but this one obviously isn’t, because its surface is too hot.” “However, gigantic planets often have natural satellites – that is, small planets that rotate around them, like the Moon rotates around the Earth,” Mr. Surdin continues. “Jupiter, for example, has several natural satellites, on which, life is quite possible. However, with the current level of science and equipment, it is practically impossible to say whether this newly discovered planet has natural satellites. The planet itself can be hardly distinguished from the Earth even with the help of a very strong telescope, to say nothing of its possible satellites.” Scientists are inclined to think that “stray planets” are a rather frequent phenomenon in the universe. The reason why so few of them have been discovered by now is because being unlighted by stars, they can be hardly distinguished. But, of course, there is hope that with the development of science and equipment, new “stray planets” may be discovered in the future. Source: Voice of Russia

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