Dubbed 138971 (2001 CB21), the asteroid can measure up to 1.3 kilometers (0.81 miles) across, about four times the size of the Eiffel Tower and about the size of the Golden Gate Bridge.
Astronomer Gianluca Masi of Italy’s Virtual Telescope Project detected the 2001 asteroid CB21 on January 30, when it was more than 21.5 million miles from Earth.
NASA’s Center for Near-Earth Object Studies (CNEOS) classifies the asteroid as a “Potentially Hazardous Asteroid (PHA)” according to the Space Reference Organization.
2001 CB21 is also classified as a near-Earth asteroid (NEA), based on its predicted relative closest distance of 4,911,102 million kilometers (3,051,617 mi) when passing by Earth.
To put that in perspective, the asteroid passed Earth at about 13 times the distance between Earth and the Moon.
The asteroid is classified as a small Apollo-class asteroid (APO) because its orbit will pass through Earth’s orbit.
Further classification of APOs is also based on the size of the asteroid.
According to the Space Reference, 2001 CB21 orbits the sun every 384 days (1.05 years).
In fact, there was an asteroid flyby last month. A large PHA-classified asteroid named 1994 PC1 passed Earth safely on January 18.
The asteroid is estimated to be 1 kilometer (0.6 miles) in size and more than twice the height of the Empire State Building, according to EarthSky.
The aforementioned asteroid was first discovered in 1994.
Another asteroid, 99942 Apophis, is 1,120 feet (0.34 kilometers) in size and will make a close encounter with Earth on April 13, 2029.
Discovered in 2004, Apophis will pass by Earth just 31,000 kilometers (19,000 miles) from our planet.
Apophis is considered one of the most dangerous asteroids that could hit Earth because it’s estimated to be close enough to pass by in 2029.
No planet-killing asteroid has hit Earth since the Chicxulub crater asteroid that caused the fifth mass extinction about 66 million years ago.
The asteroid left a crater off the coast of Mexico, where its impact ended the dinosaurs and most other plant and animal species that lived on Earth at the time, according to the Harvard Gazette.
However, NASA is preparing for a possible future asteroid impact on Earth.
Currently, NASA is working on a program called the Double Asteroid Redirection Test (DART) mission, the main goal of which is to deflect incoming asteroids from Earth.
Launched on November 24, 2021, the DART mission is designed to evaluate kinetic impact technology by hitting an asteroid with a spacecraft and observing any changes before and after the asteroid’s orbit, according to NASA.
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