For the first time, a visitor from interstellar space has penetrated our solar system. Do not be alarmed! It is not an extraterrestrial astronaut but an asteroid, dubbed A / 2017 U1 (A as an asteroid).
Its presence was detected last week by researchers at the Pan-STARRS 1 telescope in Hawaii. For a long time it was theorized that there could be asteroids or comets able to cross the huge gap between the stars and reach our solar system, but this is the first case where such an object is observed.
At first, it was unclear what it was all about: when it was found, it was thought to be a comet and for this reason it had been termed temporarily as C / 2017 U1 (C as a comet). But subsequent observations have revealed no hairs - the characteristic cloud of gas and dust surrounding the nucleus of a comet - so the object has been designated as an asteroid.
A diameter of 400 meters
Whether it is a visitor coming from deep space, it seems certain now. Not only his trajectory, a hyperbolic orbit that will soon bring him out of the solar system, but above all the direction he comes from: he has come almost perpendicular to the ecliptic, the plane on which all bodies revolve around the Sun. Other hyperbolic objects have been identified in the past, but all belonged to the solar system and had been pushed to escape trajectories from gravitational interaction with some planets.
Thanks to subsequent observations, astronomers have been able to reconstruct the characteristics and trajectory of A / 2017 U1. The asteroid should have a diameter of about 400 meters and be made up of more ice than rocks. It came from the direction of the Lira constellation, at a speed of almost 100,000 km / h - the double of the New Horizon probe we sent to Pluto - and reached the plane of the ecliptic, near the orbit of Mercury. The passage near the Sun then changed its trajectory by pushing it outward, just above the ecliptic.
He approached the Earth
On October 14, the asteroid approached the Earth, passing less than 24 million km (about 60 times the Earth-Moon distance), a "close encounter" on a cosmic scale. He has surpassed the Earth's orbit by pointing to the more outer planets. Thanks to the thrust received by the severity of the Sun, it has further increased its speed and in a few years will definitely leave the solar system pointing in the direction of the constellation of Pegasus.
Scientists are using several telescopes to try to study A / 2017 U1 before it goes too far and disappears forever. It is interesting to understand the composition and the similarities, or differences, with similar objects belonging to our solar system, but also to understand how many of these objects are able to cross interstellar space, because this information would be extremely useful for calculating any risks to our planet.