The 1.2 mile-wide asteroid, officially named (52768) 1998 OR2, safely flew past our planet today 16 times farther than the Moon is. Despite being about 3.9 million miles (6.29 million km) at its closest, astronomers have dubbed the asteroid’s trajectory a “close approach”. US space agency NASA considers any asteroid to be close to Earth if it passes within 0.05 au of the planet – that is about five million miles (eight million km).
Astronomers have tracked this asteroid for 22 years now and are certain it does not pose any threat to Earth for at least 200 years.
Instead, the flyby allowed scientists to study the space rock up close – in astronomical terms.
The asteroid was, for instance, tracked by the robotic telescope service Slooh.
The asteroid was followed by two Planewave 17-inch telescope’s from Slooh’s facilities in Chile and the Canary Islands.
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The stream kicked off today at midnight and lasted for more than one hour.
In case you missed the live event, you can relive it here on Express.co.uk, courtesy of Slooh.
Simply hit play on the embedded YouTube video player.
Slooh astronomer Paul Cox said during the stream: “When an asteroid like this comes so close to Earth, it comes within the range of our radio telescopes.
“And in this particular case, the Arecibo radio telescope, which is my favourite thing because it’s in my favourite film Contact.
“It falls within the range of radio telescopes and they can use radar and radio waves to make this kind of radio observation from it.
Up until this approach, we didn’t know how big this thing was
Paul Cox, Slooh astronomer
“This means that when they come this close, we can determine how big they are, and the shape they are.
“And up until this approach, we didn’t know how big this thing was.”
Before the Arecibo Observatory in Puerto Rico took radar images of the asteroid this month, NASA had a pretty generous estimate for the rock’s size.
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The US space agency placed the rock somewhere between 1.1 miles and 2.54 miles (1.8km and 4.1km) across.
But thanks to the Arecibo Observatory, we now know the asteroid only measures about 1.2 miles (2km) in diameter.
Astronomers have also learned the asteroid rotates once every 4.1 hours.
Mr Cox said: “The only thing we can actually measure it on, is the object’s apparent magnitude, it’s brightness.
“But as soon as it comes within the range of radar, as it’s done now, we can tell very, very specifically because we know what distance the object is and we can measure it very accurately.”
The asteroid was first observed in 1998 by NASA’s Near-Earth Asteroid Tracking programme.
Since then, astronomers have determined “with confidence” OR2 does not pose any danger to Earth for at least the next 200 years.
NASA said: “Close approaches by large asteroids like 1998 OR2 are quite rare.”
Asteroid OR2 will come much closer to Earth again in 2079, at about four times the distance to the Moon, but even then, NASA does will not have to sound the alarm bells.
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