Where can you watch the asteroid?
The asteroid should already be visible through telescopes, according to Sky & Telescope magazine.
Kelly Beatty, senior editor at the magazine, said: “Despite some interference from moonlight, 3122 Florence should be fairly easy to spot in even modest backyard telescopes.”
Sky & Telescope has detailed charts to help with locating the asteroid on its website.
You can also live stream Asteroid Florence online for free. The Virtual Telescope Project will begin a free webcast from 8.30pm tonight.
Online observatory Slooh will also broadcast a live stream of the asteroid on its website from 2am on September 1.
Slooh said: “At the moment of Florence’s approach, Slooh will train its telescopes on the asteroid to bring you its close pass live, along with commentary from our team of astronomers and asteroid experts.
“We’ll be discussing the importance of studying Near-Earth Asteroids like Florence, not only for what they can reveal about our Solar System’s past, but also due to the threat they pose to our planet.
“Although 3122 Florence doesn’t pose an immediate threat to us, an impact by an asteroid its size would be catastrophic.”
The Barkeep Observatory in Israel will also webcast live views on its website from 3-6pm on September 1.
The best time to see the asteroid will be in the late evening, with a peak brightness expected tonight. The asteroid should be almost as bright for several days before and after the end of the month.
The asteroid, named after Florence Nightingale, was first discovered by astronomer Schelte “Bobby” Bus in 1981.
Paul Chodas, manager of Nasa’s Center for Near-Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory, said: “While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller.
“Florence is the largest asteroid to pass by our planet this close since the NASA program to detect and track near-Earth asteroids began.”