Asteroid 2023 BU has just passed a few thousand kilometers from Earth. Here’s why it’s exciting

There are hundreds of millions of asteroids in our solar system, which means that new asteroids are discovered quite frequently. This also means that close encounters between asteroids and Earth are quite common. Some of these close encounters end with the asteroid impacting Earth, sometimes with serious consequences.

A recently discovered asteroid, named 2023 BU, hit the headlines because today it passed very close to Earth.

Discovered on January 21 by amateur astronomer Gennadiy Borisov in Crimea, 2023 BU only passed about 3,600 km from the Earth’s surface (near the southern tip of South America) six days later. , January 27.

This distance is slightly greater than the distance between Perth and Sydney and is only about 1% of the distance between Earth and our Moon.

The asteroid also passed through the region of space that contains a significant proportion of the man-made satellites orbiting Earth.

All of this makes 2023 BU the fourth-closest known asteroid encounter with Earth, ignoring those that impacted the planet or our atmosphere.

How is 2023 BU considered an asteroid and a threat? 2023 BU is unremarkable except that it passed so close to Earth. The diameter of the asteroid is estimated to be only 4–8 m, which is at the small end of the asteroid size range.

There are probably hundreds of millions of such objects in our solar system, and it’s possible that 2023 BU has approached Earth several times before in the millennia. Until now we have been oblivious to the fact.

In context, on average, an asteroid 4 meters in diameter will impact the Earth every year and an asteroid 8 meters in diameter approximately every five years. Asteroids of this size pose little risk to life on Earth when they strike because they largely break up in the atmosphere. They produce spectacular fireballs and some of the asteroids can reach the ground as meteorites.

Now that 2023 BU has been discovered, its orbit around the Sun can be estimated and future visits to Earth planned. It is estimated that there is a 1 in 10,000 chance that 2023 BU will impact Earth between 2077 and 2123.

So we have little to fear from 2023 BU or any of the many millions of similar objects in the solar system.

Asteroids must be larger than 25m in diameter to pose a significant risk to life if they collide with Earth; to challenge the existence of civilization, they would have to be at least a kilometer in diameter.

It is estimated that there are less than 1,000 such asteroids in the solar system and that they could hit Earth every 5,00,000 years. We know more than 95% of these objects.

Will there be closer asteroid passes? 2023 BU was the fourth closest pass of an asteroid on record. The three closest passes were made by very small asteroids discovered in 2020 and 2021 (2021 AU, 2020 HQ and 2020 VT).

Asteroid 2023 BU and countless other asteroids have passed very close to Earth during the solar system’s nearly five billion years of existence, and this will continue into the future.

What has changed in recent years is our ability to detect asteroids of this size so that any threat can be characterized. That an object about 5m in size can be detected thousands of miles away by a very dedicated amateur astronomer shows that the technology to make significant astronomical discoveries is within reach of the general public. It’s very exciting.

Amateurs and professionals can continue to discover and categorize objects together, enabling threat analysis. Another very exciting recent development came last year, with the DART (Double Asteroid Redirection Test) mission, which successfully collided a spacecraft with an asteroid and changed its direction.

DART makes plausible the concept of redirecting an asteroid away from a collision course with Earth if a threat analysis identifies a serious risk with enough warning.