Earlier this week, NASA announced that a giant asteroid is expected to pass Earth (at a safe distance) on June 6. The asteroid is estimated to be between 250-570 meters in diameter, according to NASA’s Jet Propulsion Laboratory (JPL). A Near-Earth Object (NEO), the asteroid is called 163348 (2002 NN4) and is classified as a Potentially Hazardous Asteroid (PHA).
What are Near-Earth Objects (NEOs), why are they studied?
NEOs occasionally approach close to the Earth as they orbit the Sun, NASA’s Center for Near-Earth Object Study (CNEOS) determines the times and distances of these objects as and when their approach to the Earth is close.
NASA defines NEOs as comets and asteroids nudged by the gravitational attraction of nearby planets into orbits which allows them to enter the Earth’s neighbourhood. These objects are composed mostly of water ice with embedded dust particles.
The scientific interest in comets and asteroids is largely due to their status as relatively unchanged remnant debris from the solar system formation process over 4.6 billion years ago. Therefore, these NEOs offer scientists clues about the chemical mixture from the planets formed.
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Significantly, among all the causes that will eventually cause the extinction of life on Earth, an asteroid hit is widely acknowledged as one of the likeliest. Over the years, scientists have suggested different ways to ward off such a hit, such as blowing up the asteroid before it reaches Earth, or deflecting it off its Earth-bound course by hitting it with a spacecraft. NASA’s Near-Earth Object Observations Program finds, tracks and characterises over 90 per cent of the predicted number of NEOs that are 140 metre or larger in size (larger than a small football stadium).
NASA maintains that objects of this size and larger pose a risk to Earth of “the greatest concern” due to the level of devastation that the impact is capable of causing. Further, no asteroid larger than 140 metre has a “significant” chance of hitting the Earth for the next 100 years, less than half of the estimated 25,000 NEOs that are 140 metres or larger in size have been found to date.
What is 163348 (2002 NN4)?
This asteroid is classified as a PHA, which means the asteroid has the potential to make threatening close approaches to the Earth. Asteroids with a minimum orbit intersection distance (MOID) of about 0.05 (AU is the distance between the Earth and the Sun and is roughly 150 million km), which is about 7,480,000 km or less and an absolute magnitude (H) of 22 (smaller than about 150 m or 500 feet in diameter) or less are considered PHAs.
Even so, it is not necessary that asteroids classified as PHAs will impact the Earth. “It only means there is a possibility for such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the close-approach statistics and thus their Earth-impact threat,” NASA says.
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2002 NN4 was discovered in July 2002 and is expected to approach the Earth on June 6.
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