It is called 1I/2017 U1('Oumuamua) and it recently flew past our Sun.
Last month, a mysterious object (an artist's impression courtesy of ESO can be seen above) flew past our Sun which had astronomers scratching their heads as to what it was and where it was from. Following an investigation, it is now believed this is an interstellar object and our solar system's first confirmed interstellar asteroid.
How can you tell that an object originated from a solar system other than our own? By its orbit. The object, which has been named 1I/2017 U1('Oumuamua), has an orbit that is near impossible to achieve if it is from our own solar system. This high "orbital eccentricity" as it is called, therefore suggests the most likely explanation is 'Oumuamua made the journey from outside our solar system.
As The Guardian reports, 'Oumuamua is Hawaiian for "messenger" or "scout." The object formed around another star, but it is very similar to comets and asteroids astronomers have analysed before from our own system. That suggests other solar systems are made up of similar planetary compositions, which therefore bodes well for other Earth-like planets being out there.
Oumuamua interstellar asteroid
As for the composition of 'Oumuamua, it's red in color and absorbs 96 percent of the light that falls on it. This suggests carbon-based organic molecules and therefore the potential for life in whichever system formed 'Oumuamua. In terms of size and shape, the object is roughly 400 meters in length and extremely elongated (10:1 axis ratio), making it look like a thin line in captured images. According to Wikipedia, 'Oumuamua is travelling at roughly 58,900mph and its direction suggests it came from the star Vega in the constellation Lyra.
A paper published by Nature and led by Karen Meech at the University of Hawaii puts this discovery in perspective, "None of the approximately 750,000 known asteroids and comets is thought to have originated outside our Solar System, but formation models suggest that orbital migration of the giant planets ejected a large fraction of the original planetesimals into interstellar space."
The paper goes on to suggest that the presence of 'Oumuamua means our current estimates of how many interstellar objects there are within our solar system are "pessimistically low. So we should probably expect many more of these interstellar visitors to get spotted now we are looking for them.
