A relatively small asteroid today is expected to miss Earth by only 12,000 kilometers. It may sound like a great distance, but it’s a huge miss compared to most asteroids.
The asteroid was named 2021GW4 and is estimated by NASA to be about 16 feet in diameter.
According to Mike Murray, an astronomer at Delta College’s Planetarium, a 16-foot asteroid is likely to break up into very small pieces. If the asteroid consisted of nickel and iron, it would have a much greater chance of reaching ground.
While Asteroid 2021GW4 is going to miss Earth, Murray says: ‘If a 16-foot asteroid hit the ground, it could make a crater about 60 feet. Although it sounds great, it will only be felt in the local area from the impact. It would be more like a local explosion. ‘
By comparison, the asteroid over Chelyabinsk, Russia, in 2013 was about 55 feet in diameter, and that did not even make it as a whole piece that hit the ground.
According to Murray, NASA’s predictions about asteroid trajectories are very accurate, at least in a 24 hour forecast. Murray says there is therefore virtually no chance of a wrong prediction.
But Murray is excited about any asteroid that almost misses. He says we learn a lot from these close passes. We learn how it comes from knowing its trajectory. By working its orbit backwards, astronomers can find out where the asteroid comes from in our solar system.
We learn about its shape by bouncing radio waves, or RADAR, at the asteroid.
If we can get enough reflected light from the asteroid, scientists can do a spectral analysis that will tell us the composition of the surface of the asteroid.
I asked Murray if any asteroid was currently worrying him, and he said no, but with a slight hesitation. The only asteroid that Murray is worried about right now is an asteroid that has not yet been detected. There are probably many more asteroids that have not yet been discovered. A good example is the asteroid that hit Russia in 2013.
An asteroid named Apophis has recently been considered a nuisance to Earth. The latest NASA forecast shows that Apophis will not come close to Earth for at least 100 years. Apophis is about 1,320 feet in diameter.
According to Murray, an asteroid with an extinction size is estimated to be about six kilometers in diameter.
NASA’s Jet Propulsion Laboratory explains it this way: “Asteroids are rocky fragments left over from the formation of the solar system about 4.6 billion years ago. Most asteroids orbit the Sun in a belt between Mars and Jupiter. Scientists think there are probably millions of asteroids, ranging largely from hundreds of kilometers to less than one kilometer (slightly more than half a mile) wide.
Sometimes the orbital paths of asteroids are affected by the gravity of planets, which causes their paths to change. Scientists believe that stray asteroids or fragments of earlier collisions struck the Earth in the past and played an important role in the evolution of our planet. ”