Giant asteroid to pass closely by Earth

A massive asteroid, 2.7 miles in size, will pass relatively close to Earth on Friday, but experts say it's still far enough away to pose no threat. 

The asteroid Florence will cruise by 4.4 million miles from Earth, according to NASA's Center for Near Earth Object Studies. In comparison, the moon is about 240,000 miles away.

"I'm not losing any sleep over Florence," said Carrie Nugent, scientist at Cal Tech/IPAC and author of "Asteroid Hunters." "Although it is going to make a close swing nearby the Earth and the moon [...] we know exactly where it's going and there's no concern it's going to go anywhere else." 

Named after Florence Nightingale, the asteroid and its orbit have been known since 1981 when it was spotted by a scientist at the Siding Spring Observatory in Australia. 

Near-Eath objects are common: we know of 16,587 in total. But it's the size of Florence that makes it notable as it's one of the largest objects ever identified.

While there's no chance that it'll crash into Earth on this pass, there's still important science work to be done. Radio telescopes in Puerto Rico and California will follow the asteroid closely, revealing details as fine as 30 feet in size. Scientists will then use the data to try and better understand the asteroid's composition and structure.

Enthusiasts will be able to view Florence with backyard telescopes, an opportunity that they might want to take advantage of, given this is the closest the asteroid will be for the next 500 years. But you'll have to get up early: the flyby will be at 5 a.m. PDT.

For the morbidly curious, when compared to the asteroid that killed the dinosaurs, Florence is small. Scientists believe that the asteroid that crashed into the Yucatan Peninsula was about 6.7 miles wide, about the cruising altitude of a 747 jet.

"You can imagine yourself taking a plane flight, sitting in a window seat, looking out your window, and imaging a rock so big that, starting on the ground, it goes all the way up to your wingtip. And it takes your plane a minute to fly past it," Nugent said.

If scientists were able to spot an asteroid before it crashed into Earth, the public would likely hear from NASA's Planetary Defense Coordination Office, which is dedicated to spotting and formulating responses to objects that might come in contact with our planet.