In a rare celestial event over Europe, skywatchers will be able to see an asteroid briefly block out the light from a star as it passes in front of the star Thursday night.
It may be the only asteroid eclipse that will take place this century, observable with the naked eye.
A similar situation like a solar eclipse can happen with asteroids — the sun-orbiting, rocky or metallic objects that are left over from the formation of the solar system.
About 400,000 of these dark bodies, from a few hundred kilometres to just a few metres wide, are known to exist. The smaller ones are hard to detect.
More than 6,500 are Near Earth Objects — their orbits come close to that of earth’s.
Such objects could potentially hit earth and, depending on their size, produce considerable damage.
While an asteroid is far too small to cover the sun, one will occasionally move directly in front of one of the many stars in the night sky and block its light from view, causing a stellar occultation.
Since asteroids move relatively fast, these events typically last just a few seconds. Normally the occulted star is so faint the event can only be seen via telescope.
During Thursday-Friday night, however, a star visible to the naked eye, Delta Ophiuchi (the fourth brightest star in the constellation Ophiuchi), will be occulted by asteroid Roma, which is about 50 km across, according to a statement of the European Space Agency.
This means the occultation will be visible only along a path about 50 km wide, crossing central Europe, Spain and the Canary Islands.