Surely more than one movie buff and science fiction fan will have come to mind the image of the monolith from the 2001 film: a space odyssey , which is precisely about to turn fifty, or the alien ships from The Arrival . Nicknamed ‘Oumuamua – its official catalog name is 1l / 2017 U1 -, the first asteroid from outside the Solar System detected to date can recall those mysterious objects: narrow and elongated, it has also been compared to a cigar or a pen .
The interstellar rock find, announced in the journal Nature , actually occurred on October 19. That day, the Pan-STARRS 1 telescope, located in Hawaii, captured a faint light signal in the sky that scientists initially took to be a conventional asteroid.
But calculations on its orbit revealed that ‘Oumuamua -‘ the first messenger from afar ‘, in Hawaiian – had not originated in the Solar System, like all other asteroids and comets. And additional observations ruled out cometary activity as it passed the Sun last September. Confirmed: it was an interstellar asteroid, a true piece of astronomical big game, traveling at a speed of 95,000 kilometers per hour .
Next, the team led by Karen Meech, from the Hawaii Institute of Astronomy, analyzed the data gathered by the Very Large Telescope (VLT) of the European Southern Observatory (ESO) and other large telescopes to try to make a portrait-robot of ‘Oumuamua . And the first thing that caught their attention is that its brightness multiplied by ten when it rotated on its axis, every 7.3 hours. This means that the asteroid is ten times longer – about 400 meters, they calculate – than it is wide .
They have also concluded that its color is dark red, due to the effects of cosmic rays for millions of years, and that there is not a speck of dust around it. All these features suggest that ‘Oumuamua is very dense , probably with a high metal content, with no significant trace of water or ice.
Upcoming sightings
But where does it come from? It is not known for sure. Perhaps it comes from a planetary system of the luminous star Vega , in the constellation Lyra, although it could very well be that it has been wandering the Milky Way for hundreds of millions of years without establishing “fixed residence” around any star in the galaxy. until its temporary passage through the Solar System.
The study authors will continue to observe ‘Oumuamua for the remainder of the year to answer this and other questions. “Now that we have detected the first interstellar rock, we are ready for the next one!” Says ESO astronomer Olivier Hainaut optimistically. Because as indicated in the report published in Nature , this finding suggests that estimates of the density of these types of objects may have fallen short , and that, thanks to advances in astronomical observation technology and information processing , the harvest of asteroids and comets from outer space will surely increase soon.
Photo: M. Kornmesser / ESO
