Meet Florence, the Giant Asteroid That Will Buzz by Earth This September

The 2.7-mile-long, near-Earth object will give astronomers a chance to study the asteroid up close

A Near Earth Object NASA/JPL

Now that solar eclipse-mania has passed, it’s time to get excited for another astronomical event: an asteroid passing by. On September 1, a space rock dubbed Florence will become the largest asteroid to zoom past Earth since near-Earth asteroids were discovered a century ago, reports Eddie Irizarry at EarthSky.

Measurements made by the Spitzer Space Telescope and NEOWISE asteroid-hunting instrument suggest that Florence is around 2.7 miles across, according to NASA. The asteroid will pass 4.4 million miles from Earth, about 18 times the distance from the Earth to the moon. That is a long ways, but on the galactic scale, it’s a hair's breadth.

“While many known asteroids have passed by closer to Earth than Florence will on September 1, all of those were estimated to be smaller,” Paul Chodas, manager of NASA’s Center for Near-Earth Object Studies says in the press release. NASA has tracked these near-Earth objects since 1998, and Florence tops the charts.

The space rock, officially called Asteroid 1981 ET3, was first detected at Australia’s Siding Spring Observatory in 1981 and was named Florence 3122 in honor of Florence Nightingale, the mother of modern nursing, Irizarry reports.

While there’s no chance that the asteroid will hit Earth, NASA says its size and proximity makes a perfect target for ground-based radio telescope observations, which may produce images of the asteroid with a resolution as clear as 30 feet.  

It will be clearly visible in the night sky for amateur astronomers, passing through the constellations of Piscis Austrinus, Capricornus, Aquarius and Delphinus beginning on August 27.  “[Its] visible magnitude of 9 is really bright,” Rüdiger Jehn, co-manager of the European Space Agency’s Near Earth Object segment tells Ryan F. Mandelbaum at Gizmodo. “Every amateur astronomer will be able to see it.”

Florence isn’t the first or last asteroid to dance with Earth this year. In January of 2017, asteroid AG13 snuck up on astronomers. The space rock was between 36 and 111 feet wide and passed Earth at half the distance to the moon. Another asteroid in the same size range, 2012 TC4 is scheduled to pass roughly one-fourth the distance to the moon—between 4,200 miles and 170,000 miles—on October 12, 2017.

Currently, NASA is tracking 1,826 near-Earth objects classified as Potentially Hazardous Asteroids, which have some risk of striking our planet in the future. Among those, reports Irizrarry, are several even larger than Florence, including 1999 JM8 at 4.3 miles across, 4183 Cuno at 3.5 miles across and 3200 Phaeton at 3.2 miles across. But none has come as close as Florence will next month.

There's no chance the space rock will collide with Earth anytime soon. Florence won’t make a closer pass until around the year 2500.