Close Encounters of star-like

According to a recent study conducted by astrophysicist Coryn Bailer-Jones of MPI, the star HIP 85605 is approaching our solar system in a flyby that will take place no earlier than 240-470 thousand years. The research, which is based on the analysis of stellar close encounters in the Milky Way, has the purpose of studying those potential impacts of celestial origin that have occurred in the past on our planet and is part of a wider scientific program.
It is known by the acronym HIP 85605, and it is one of the two stars that form a binary system located about 16 light-years away in the constellation of Hercules. If the calculations of Coryn Bailer-Jones from the Max Planck Institute for Astronomy in Heidelberg, Germany, are correct, it is in route of approach with our Solar System. No panic for humans because the good news is that the star, which will arrive at the minimum distance of 0.04 parsecs (equivalent to about 8000 times the Earth-Sun distance), will have no influence neither on this planet nor on others and most importantly, this “close encounter” will take place no earlier than 240-470 thousand years.


Credit: ESA

“Although the Milky Way contains many stars,” says Bailer-Jones, “the space between them is very great. Therefore, the probability that two stars can get to a real collision is extremely small. “However, in astronomical terms, such events represent almost missed meetings. In fact, considering that the Universe extends for 46 billion light years in all directions, which is the part of observable space, such an event that is expected to occur to a distance of 50 light-days is considered quite near. If we consider the temporal context, 250-500 thousand years are considered certainly a real future.
The real concern, however, is given by the impact of the transfer of HIP 85605 that may determine the Oort Cloud, i.e. that immense cloud formed by numerous planetesimals ice that surrounds the solar system. Because of its distance from the Sun varies from 20,000 to 50,000 astronomical units, HIP 85605 should cross the Oort Cloud causing some disruption. In fact, many planetesimals could be wiped out in interstellar space while others might be diverted to the inner regions of the solar system, in particular in route to Earth. Now, assuming that humans still exist during these ancient times, this could be a big trouble, even if the event will be released in a period of the order of a million years.
But these “close encounters of star-like” are very rare. Collisions between stars, typically occur in binary systems where there are dense objects and collapsed, that white dwarfs or neutron stars. “The exception is given by a close binary system,” says Bailer-Jones. “It can happen, and it happens, that a star expands during its evolution influencing the companion star. A binary system consisting of two neutron stars can even get to the merger. ‘Of course, on the astronomical time scale flyby of two stars while they perform their “cosmic dance” is a very common phenomenon. As part of the study conducted by Bailer-Jones on a sample of more than 50,000 stars, it is expected that only HIP 85605 will arrive within 1 parsec from the Sun between next 240-470 thousand years. In his article, the researcher then indicates (with a confidence level of 90%) that the last meeting of this kind happened 3.8 million years when γ-Microscopii, a giant star-type spettale G7 and mass equal to 2.5 solar masses, he arrived at a distance of 0.35 to 1.34 parsecs from the solar system, an event that could significantly disturb the Oort Cloud.

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