Author: Yangguang Ou
Institution: Florida State University
Early Monday, astronomers confirmed the passing of an asteroid a mere 45,000 miles above the Earth's surface. This distance is about twice as high as the locations of most satellites that orbit the Earth in free fall, but about only one-fifth the distance between the Earth and its moon. Although it passed somewhere over the Pacific Ocean and did not reach the Earth's surface, it did receive some publicity among the scientists. "It's pretty unusual to see one this close," said Timothy Spahr, an astronomer at Harvard University, "if an object of this size were to impact the Earth, it would be equivalent to a small nuclear explosion."
Spahr, director of the Minor-planet Center at the Harvard-Smithsonian Center for Astrophysics in Cambridge, received news of the asteroid's arrival late Friday. According to the Boston Globe, the asteroid called 2009 DD45 was estimated to be 20 yards long by 30 yards across, the same size as the asteroid that burned up in Siberia and caused what came to be known as the "Tunguska Event." This event, which occurred on June 17, 1908, witnessed the destruction of 80 million trees over an area of 2,150 kilometers, approximately half the size of the state of Rhode Island. From eye-witness accounts, the explosion occurred in the air rather than on the ground though, according to astronomers, it was still in the category of "an impact". The energy released in this event, estimated by the scientists who investigated the site, was roughly 1,000 times more powerful than the atomic bomb dropped on Hiroshima, Japan. Furthermore, the resulting earthquake was estimated later on to have been a 5.0 on a Richter scale. The change in atmospheric pressure as a result of the impact, according to the scientists, was felt as far as Great Britain.
Spahr said that even though impact from an asteroid the size of 2009 DD45 would potentially be catastrophic, this was not what concerns him the most: "Now if an asteroid that was, say, a kilometer across were to strike the earth, that could result in mass extinction." The impact from a giant space object is in fact one of the leading explanations to the extinction of dinosaurs approximately 65 million years ago.
Brian Marden, a senior astronomer at the Minor-planet Center, said that many celestial objects of the size of DD45 frequently pass the Earth but go unnoticed: "No one is watching the whole sky all the time." Marden explained in an interview to the Boston Globe that the presence of light, like those from the celestial bodies such as the full moon, greatly reduces astronomers' visibility of small objects in outer space. Fortunately, meteorites the size of a kilometer ought to be visible several years in advance.
According to the Boston Globe, the next meteorite the size of DD45 will approach Earth in the year 2029. The asteroid, known as 99942 Apophis, is expected to come within approximately 20,000 miles of the Earth's surface.
Written by: Yangguang Ou
Edited by: Brittany Raffa (News and Features Editor) and Renee Gilberti (Professional Reviewer)
Published by: Hoi See Tsao