Asteroids are rocky pieces that were left over when the solar system formed approximately 4.6 billion years ago. The Nasa Joint Propulsion Laboratory states that an asteroid is considered to be close to Earth if it is less than 1.3 times the distance between Earth and the Sun, which is around 93 million miles away (JPL).
On December 15, 2015 RN35 will safely approach Earth at 08:12 UTC (09:12 CET), travelling at a distance of 686 000 km, or a little under two lunar lengths.
The best viewing will be in the Southern Hemisphere during the close approach, but Europe will get some opportunities over the coming days until around December 19.
"2015 RN35 will not shine bright in the skies. There’s not a single asteroid out there that isn’t interesting. Near-Earth asteroids fascinate ESA’s Planetary Defence Office in particular because they give us key insights into the composition and trajectory of potentially hazardous objects," ESA said in a statement.
Astronomers are interested in the asteroid because there isn't much information about it and nobody knows what it is comprised of. No one is certain of its composition, exact size if it is rotating on its axis, or even the specifics of its orbit, according to the ESA.