Who deformed the outer Solar system: star-the intruder or the "ninth planet"?

In the far reaches of our Solar system lies the conundrum. For a long time astronomers believed that the eight planets rotate on almost perfect circular orbits, because once formed in a swirling disc of dust and gas surrounding the young sun. But in 2003, scientists discovered something strange: a dwarf planet Sedna has a strange orbit, changing the position of the two distances to Pluto to more than twenty distance to the Sun. And she's not alone. For years astronomers have discovered nearly two dozen distant icy objects whose orbits are oblong and strangely tilted compared to the plane of the Solar system.

To explain these oddities, scientists have suggested that perhaps these worlds — the brutal scars of the past. Perhaps one day in his youth, the Solar system passed close to a star knocked off course these worlds. Or distant ninth planet by its gravity violated the order in our system.

The Latter hypothesis gained weight over the past few years, forcing the first to smell the dust, says Suzanne Pfalzner, the astronomer of Institute of radio astronomy to them. Max Planck in Germany. Anomalies in the orbits of several small objects of the outer Solar system have accumulated evidence that "the ninth planet" is about 10 times more Land mass. Meanwhile, the intruder star was considered too unlikely — until now. Pfalzner and her colleagues recently published a paper on the Preprint server arXiv, which was adopted by The Astrophysical Journal, in which he showed that the stars can fly in the neighborhood of our Solar system much more often than thought. These results not only give weight to the theory of stellar flight, but can also explain how the "ninth planet" to his strange orbit.

the Strange orbit of Sedna

Astronomers know that the Sun wasn't always so lonely. It was born in a cluster of hundreds or tens of thousands of stars that were scattered across the galaxy in just 10 million years. Therefore, while our Sun was in this cluster, the stars scurried back and forth in a dizzy dance, which could easily lead to the aerial in our nascent solar system. But after a gap of congestion on parts of the likelihood of such an invasion has fallen to almost zero. Anyway, thought so. But Pfalzner and her colleagues are now saying that the chances of invasion remained relatively high after the accumulation began to fall apart. After many long computer simulations they found that the star mass of our Sun with a probability of 20-30% could fly 50 — 150.e. from Pluto (1 and.e. is the distance from the earth to the Sun, approximately 150 million kilometers). Of course, such a close approach shook our young Solar system.

Although large planet would be untouched (the Sun, for example, is almost not felt the weak gravity of the eight planets), the invasion could move small objects by placing them on a strange orbit in the Solar system. Moreover, the simulation recreated the second trend that astronomers observed in the Solar system — the tendency of external objects to be grouped together. They move together in close groups. In simple words, star-intruder fits perfectly in a model created on the basis of observations.

"But they will last for 4.5 billion years", that is, until there is a Solar system, "is the million-dollar question," says Scott Kenyon, an astronomer at the Harvard-Smithsonian center for astrophysics, not involved in the study. And Pfalzner agree with him. She would like to model long-term behavior in order to understand whether the changes caused by the star's invasion, for the entire lifetime of our system.

Scientists are avidly searching for new data using a number of different observing campaigns. Some teams, for example, have combed through large chunks of the heavens in search of oddities in the outer Solar system. Scott Sheppard, an astronomer at the Research of the Carnegie institution who was not involved in the study, could not contain their excitement on the eve of the launch of the Large SYNOPTIC telescope is an 8.4-meter dish, which will open up hundreds of new solar systems.

Kenyon, meanwhile, hopes that the spacecraft Gaia, which is in the process of clarifying the provisions of a billion stars with unprecedented precision, will help you find brothers and sisters of our star. This will allow scientists to better understand star cluster, which has formed our young Solar system, and the likelihood that another star comes too close. "Gaia" is our new Savior," he says. A recent study Gaia allowed us to track the path of nearby stars in the past and projecting them into the future, only to discover that 25 stars can come dangerously close to our home for 10 million years. And, of course, everyone wants to find the "ninth planet."

But Pfalzner argues that the opening of another major member of the Solar system does not preclude the starry span. "It's not a script either/or," she says. "If the ninth planet exists, it does not exclude the model of stairs, rather in her favor." The projected orbit of the ninth planet, an eccentric and tilted (relative to the plane of the Solar system) also could be formed under the action of stellar flight. The discovery of the ninth planet will put a lot of points over i.