Here's how close a two-mile long asteroid will come to earth on Wednesday - and if you should be worried

This week, a giant asteroid will hurtle towards our planet, and will be visible from Earth as it comes chillingly close to us. Officially named 1998 OR2, the space rock is described as "half the size of Everest", and will fly by at almost 19,500 miles per hour on Wednesday (29 April). Here's everything you need to know about it: How big is 1998 OR2? Asteroid 1998 OR2 is thought to be sized between 1.8 and 4.1 kilometres in diameter. That's roughly 0.5 to 2.5 miles. The higher end of that estimate suggests the space rock could be around half the size of Mount Everest, and taller than Japan's Mount Fuji. How close will it come? Asteroid 1998 OR2 will buzz the planet just 3.9 million miles from its surface. This may sound far away, but in space terms, it's relatively near, close enough to be considered a "Near Earth Object" (NEO) by NASA. The space agency considers anything passing within 120 million miles of Earth a NEO. How can I see the asteroid? Unfortunately, the won't be visible with the naked eye. But if you have a telescope handy at home, you should be able to see 1998 OR2 as it skims passed earth. For those without, you can actually watch the asteroid pass us online, as the Virtual Telescope Project in Rome will host a free public viewing of the asteroid. Is it dangerous? Despite being considered a 'Near Earth Object' a "potentially dangerous" as a result of its size and proximity to earth, the chances of 1998 OR2 colliding with Earth are very slim indeed. However, our planet's in for an even closer shave in around 60 years time, when 1998 OR2 is expected to pass within just one million miles of Earth. NASA discovers roughly 30 NEOs every week. The space agency explained, “Experts estimate that an impact of an object the size of the one that exploded over Chelyabinsk, Russia, in 2013 – approximately 55 feet (17 metres) in size – takes place once or twice a century. “Impacts of larger objects are expected to be far less frequent (on the scale of centuries to millennia). However, given the current incompleteness of the NEO catalogue, an unpredicted impact – such as the Chelyabinsk event – could occur at any time.” Nothing has struck earth with apocalyptic damage for 66 million years, when an asteroid wiped out the dinosaurs. Asteroids are large rocks that orbit around the sun. Often, due to gravitational pulls from planets, they can be moved off course and can collide with planets and other debris in space. They differ to meteors, which are smaller rocks that fly around our solar system. When these crash down through earth's atmosphere, they burn up and vaporise, causing what we know as a "shooting star".