A large asteroid discovered three years ago whizzed past Earth today, but there's no need to panic.

The asteroid — named 2014 JO25 — ranged between more than 700 metres and 1.4 kilometres across. At its closest, the asteroid passed roughly 1.8 million kilometres from Earth — or more than four times the distance from Earth to the moon.

Early radar images obtained by NASA showed the asteroid had two lobes, with the largest one measuring about 620 metres across.

The asteroid was discovered in May 2014 as part of the Catalina Sky Survey near Tuscon, Ariz. The survey is part of NASA's Center of Near-Earth Object Studies program, which is constantly searching for asteroids that could pose a danger to Earth one day.

Visible from Earth

The asteroid has twice the reflectivity the moon does, though little else is known.

After the sun sets on Wednesday, the asteroid should be visible to those using a small telescope. It's expected to be visible for two days before it moves away from Earth.

Earth passes through debris every day, with an estimated 90 tonnes of meteoroids entering our atmosphere. Those pieces that are larger burn up in our atmosphere, and can be seen streaking across the sky. 

Then there are pieces of debris far larger than meteors, known as asteroids, that range from a few feet across to kilometres. These pass within this distance of the planet more frequently, sometimes a few times a week. But objects as large as 2014 JO25 are rare.

The last asteroid of similar size or larger to pass this close to Earth was Toutatis in September 2004; it was roughly five-kilometres wide and passed within four lunar orbits. The next big one to pass this close will be 1999 AN10, measuring 800 metres wide. It will pass as close as one lunar distance, roughly 380,000 kilometres, in 2027.