Photo Shows Potentially Hazardous Asteroid Before It Passes Earth Next Week

An asteroid classed by astronomers as "potentially hazardous" is due to make a relatively close—but safe—approach to Earth next week.

The space rock, called 138971 (2001 CB21), is estimated to be up to 3,940 feet in diameter, making it significantly bigger than the tallest building in the world, the Burj Khalifa in Dubai, which stands at around 2,720 feet.

The asteroid is expected to reach its closest point to Earth on March 4 at 2:59 a.m. Eastern Time, at which point it's estimated that it will be traveling at more than 26,800 miles per hour, according to NASA's Center for Near-Earth Object Studies (CNEOS).

However, it won't pose any danger to us. The asteroid isn't expected to get any closer than about 3 million miles to Earth, which is more than 12 times further away than the moon.

In addition, the asteroid may not be quite as large as its upper estimate suggests. There is a wide margin of error in the calculations for how big it might be, and the lower estimate is a much more modest—though still large—at 1,837 feet.

In any case, 2001 CB21 has attracted some interest and it was photographed by an astronomer at the end of January as it approached Earth from a distance of more than 21.5 million miles.

Now much closer, the same astronomer has managed to take a photo of the asteroid once again.

Gianluca Masi, an astronomer at the Virtual Telescope Project in Italy, captured the below image of 2001 CB21 on Wednesday, February 23, when it was about 6.2 million miles away.

Asteroid 2001 CB21
Asteroid 2001 CB21, pictured on February 23, 2022, by Gianluca Masi at The Virtual Telescope Project in Italy. Gianluca Masi/Virtual Telescope Project

The asteroid can be seen as a white dot in the center of the image, indicated by a white arrow. The image comes from a single 120-second exposure shot taken remotely using a PlaneWave 17" robotic telescope unit.

"The telescope tracked the apparent motion of the asteroid, so it looks like a sharp dot, with surrounding stars appearing slightly elongated," the Virtual Telescope Project website states. "On the upper left, stars of the globular cluster NGC 5466 are also visible."

A time-lapse video of the asteroid moving through space was also compiled out of 139 images collected during the observation session. It can be seen below.

Asteroid 2001 CB21
A GIF image of asteroid 2001 CB21 moving through space, put together using images by Gianluca Masi at the Virtual Telescope Project. Gianluca Masi/Virtual Telescope Project

Masi told Newsweek: "The advanced technology we use makes our
telescopes among the best ones on the planet to track and share even the
fastest, demanding asteroids.

"People often ask us why the number of near-Earth objects has apparently increased over the last [few] years. Actually, it is the continuously improving technology which is making it possible for us to spot smaller and smaller objects, which we were simply missing before."

The Virtual Telescope Project will also host a live feed of the asteroid passing overhead on its WebTV page starting on March 4 at 3 a.m. UTC (10 p.m. ET on March 3).

2001 CB21 orbits the sun, meaning it occasionally comes relatively close to Earth. After March 4, it isn't expected to come so close to Earth again until March 6, 2043, according to NASA.

Although NASA classes the asteroid as a potentially hazardous asteroid or PHA, this doesn't mean it will hit Earth—only that there is a possibility for such a threat.

PHAs are defined based on characteristics that affect the risk they pose to our planet. Generally, asteroids that can't get closer to Earth than about 4,650,000 miles or are smaller than about 500 feet in diameter aren't considered PHAs.

Asteroid in space
A file photo shows an illustration of an asteroid in space with the Milky Way in the background. Certain asteroids may be deemed potentially hazardous by astronomers, but that doesn't necessarily mean they will ever hit Earth. dottedhippo/Getty