Astronomers have discovered a planet the size no smaller than Jupiter, which has come to us from another galaxy. This is the first planetary immigrant, recorded in the Milky Way. This finding challenges the leading hypotheses to explain when and how the planets were formed.
This planet is 2,200 light-years from Earth in the so-called Helmi Stream, a ring of ancient stars, were thought not to have planets, which arrived in the Milky Way from another galaxy. According to astronomers, this thread was formed from 6 to 9 billion years ago, when the Milky Way galaxy tore another to pieces, absorbing in the process of the stars. Astronomer John Setyavan of the Max Planck Institute for Astronomy in Geydelberge, Germany, loves to watch these stars because they have unusual properties. And one of these stars is unusual in two ways. It is called HIP 13044.
Setyavan with colleagues from the Max Planck Institute and the European Space Agency have noticed that the star is moving with variable speed in relation to our sun. Their instruments recorded a repeating 16-day pattern, in which the star was then closer, then further away from us. This may be caused by spots on the star that violate accuracy or the constant expansion and contraction of the star (known as the pulsation of stars). But none of this, researchers have found. This left only one option: to this star has a gravitational influence of a planet.
Thus, it is the first foreign planet, recorded in the Milky Way, as reported by the team today in the journal Science. But this is not the only thing that astounds in her. After all, according to scientists, it could not be formed.
The fact is that HIP 13044 - this is a very old and metal-poor star. It is approximately 3 billion years older than our sun and by comparison, has a 1% stock metal. Prevailed until today hypothesis states that the evolution of stars, metals (astronomical term for all elements heavier than hydrogen and helium) in a rotating disk around them, form a small "seeds" that attracts other matter, and gradually transformed into the planet. Until today, the observations confirm this theory: metal-rich stars such as the Sun, are much more likely possessed a planetary system, compared with the poor in metal stars. "The fact that planets can form around stars with such a small quantity of this material is very unexpected and surprising," - said Christopher Johns-Krull, an astronomer at the University of Houston in Texas Rice, who was not involved in this work.
But there is another theory of planet formation. According to her, if a rotating disk of gas around the star is large enough (one-tenth the mass of a star or more), the gravitational force of the disc, according to Jones Krull, may make it unstable. In this case, forces stars lacking its retention, and it decomposes under the action of its gravity as forming the planet.
Although it is not possible to say with absolute certainty that these changes in the velocity of the star is a planet, but all the evidence suggests exactly that. In order to come to a final conclusion, the astronomers will have to conduct additional tests. Ideally, they will fix the planet, going ahead of the stars, but it will only be possible if the planet’s orbit passes a certain angle. "The statement that it is a planet from another galaxy, so far only a guess," - said NASA astronomer Stephen Prevdo. Perhaps, this star was part of the Milky Way at a time when it collided with another galaxy billions of years ago.
Although extragalactic planet, it "would be great," said Prevdo, but even more exciting is that it can affect the theory of planet formation. Johns-Krull agrees: "This planet refutes our hypothesis. Perhaps we need to reconsider our views." Popular news informers tell about the most important events of the day.