What is a near-Earth object or NEO?
Many asteroids race around the Sun on trajectories that can bring them close to our planet at different points in time.
Occasionally, asteroid and comets will come close enough to Earth for NASA’s automated systems to track their orbits.
According to NASA, an NEO is “an asteroid or comet with a perihelion distance less than or equal to 1.3au”.
One au, or astronomical unit, is the distance between Earth and the Sun – about 93 million miles (149.6 million km).
NASA said 99 percent of all discovered NEOs are asteroids.
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When will the Asteroid 52768 (1998 OR2) fly past Earth?
The space rock is expected to zip by on the morning of April 29.
NASA estimates the asteroid is racing around the Sun at speeds of about 8.7km per second or 19,461.3mph (31,320kmh).
NASA also estimates the asteroid measures somewhere between 1.11 miles and 2.54 miles (1.8km and 4.1km) across.
At its closest, the rock will shoot by from a distance of 3.9 million miles (6.29 million km).
In other words, the space rock will be about 16 times farther than the Moon is.
But astronomers expect the asteroid to be bright enough for small telescopes to pick up.
What is a potentially hazardous asteroid?
Some space rocks are big enough and bright enough to warrant observation from NASA.
NASA considers an asteroid potentially hazardous if it measures more than 492ft (150m) across and approaches Earth from within 4.6 million miles (7.5 million km).
NASA said: “A relatively small number of near-Earth objects pass close enough to Earth and are large enough in size to warrant close observation.
“That’s because the gravitational tug of the planets could, over time, cause an object’s orbital path to evolve into an Earth-crossing orbit.
“This allows for the possibility of a future collision.”
However, none of these objects are expected to strike Earth for many hundreds of years.
The US space agency said: “NASA knows of no asteroid or comet currently on a collision course with Earth, so the probability of a major collision is quite small.
“In fact, as best as we can tell, no large object is likely to strike the Earth any time in the next several hundred years.”