Astronomers have discovered more than 10,000 different space objects that travel near Earth. The comets and asteroids are called near-Earth objects, and asteroid 2013 MZ5 holds the distinction of being No. 10,000.

Asteroid 2013 MZ5 is approximately 1,000 feet, 300 meters in diameter, and its orbit does not travel near enough to Earth to pose any threat, NASA notes. The asteroid was first observed on June 18 by the NASA-funded Pan-STARRS-1 telescope, operated by the University of Hawaii.

Near-Earth Object
Asteroid 2013 MZ5 is the 10,000th near-Earth object discovered by astronomers. PS-1/UH

While astronomers have been able to observe 10,000 near-Earth objects, there are more than 100,000 such objects that have yet to be discovered. Lindley Johnson, program executive for NASA's Near-Earth Object Observations Program, noted the significance of the event and said, “There are at least 10 times that many more to be found before we can be assured we will have found any and all that could impact and do significant harm to the citizens of Earth.”

Asteroids and comets that travel within 28 million miles from the Earth are classified as NEOs, NASA notes. The majority of these objects are less than 1 kilometer, 3,280 feet across. NEO identification is important so researchers can detect any potential threats to Earth.

NASA notes that an object would need to be roughly 100 feet across in order to do significant damage to populated area, while an object that is 3,280 feet across could lead to global devastation. Of the 10,000 discovered NEOs, 1,000 are larger than 1 kilometer, but none travel close enough to Earth to be a potential impact threat. Most of these global threats have been found, NASA says, and there are just a few dozen of these NEOs that have yet to be discovered.

While most of the larger threats have been found, approximately 30 percent of NEOs, 460 feet across, that could do significant damage if they crashed into a populated area have been found, while just 1 percent of the NEOS measuring 100 feet across have been discovered. With 90 percent of NEOs posing a global threat have been discovered, astronomers are turning their attention to the objects that could pose a significant, but not catastrophic, threat.

Astronomers hope to discover 90 percent of NEOs that are 500 feet or larger that would reduce the threat of an unexpected impact to 1 percent. NASA says a known threat could be targeted and deflected from Earth.

NASA’s institution of the Near-Earth Object Observations Program has led to a significant increase in the number of NEOs discovered on a daily basis. The first NEO was discovered in 1898, and Tim Spahr, director of the Minor Planet Center, said, “These days, we average three NEO discoveries a day, and each month the Minor Planet Center receives hundreds of thousands of observations on asteroids, including those in the main-belt.” NASA states it discovers 1,000 NEOs annually. The largest NEO is asteroid 1036 Ganymed, which is 26 miles across. The next time 1036 Ganymed will travel near Earth will be on Oct. 13, 2024, at a distance of 34,774,500 miles.

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