A relatively large near-Earth asteroid will fly safely past our planet on April 19 at a distance of about 1.8 million kilometres - over four times the distance from Earth to the Moon, NASA said today.
Although there is no possibility for the asteroid to collide with Earth, this will be a very close approach for an asteroid of this size.
The asteroid, known as 2014 JO25, was discovered in May 2014 by astronomers at the Catalina Sky Survey in Arizona, US.
Contemporary measurements by NASA's NEOWISE mission indicate that the asteroid is roughly 650 meters in size, and that its surface is about twice as reflective as that of the Moon.
At this time very little else is known about the object's physical properties, even though its trajectory is well known.
The asteroid will approach Earth from the direction of the Sun and will become visible in the night sky after April 19.
It is predicted to brighten to about magnitude 11, when it could be visible in small optical telescopes for one or two nights before it fades as the distance from Earth rapidly increases, NASA said.
Small asteroids pass within this distance of Earth several times each week, but the upcoming close approach is the closest by any known asteroid of this size, or larger, since asteroid Toutatis, a five-kilometre asteroid, which approached within about four lunar distances in 2004.
The next known encounter of an asteroid of comparable size will occur in 2027 when the 800-metre-wide asteroid 1999 AN10 will fly by at one lunar distance, about 380,000 kilometres.
The April 19 encounter provides an outstanding opportunity to study this asteroid, and astronomers plan to observe it with telescopes around the world to learn as much about it as possible.
The encounter on April 19 is the closest this asteroid has come to Earth for at least the last 400 years and will be its closest approach for at least the next 500 years.
Also on April 19, the comet PanSTARRS (C/2015 ER61) will make its closest approach to Earth, at a very safe distance of 175 million kilometres, NASA said.
A faint fuzzball in the sky when it was discovered in 2015 by the Pan-STARRS NEO survey team using a telescope on the summit of Haleakala, Hawaii, the comet has brightened considerably due to a recent outburst and is now visible in the dawn sky with binoculars or a small telescope.