Context

• NASA has been tracking asteroid 465824 2010 FR, which is twice as big as the Pyramid of Giza and is expected to cross the Earth’s orbit on September 6.
• It is classified as a Near-Earth Object (NEO) and a potentially hazardous asteroid (PHA).

Key Details

• NEOs occasionally move close to the Earth as they orbit the Sun, and when this happens,
• NASA’s Center for Near-Earth Object Study (CNEOS) determines their distance.
• NASA defines NEOs as comets and asteroids nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth’s neighbourhood.
• These objects are composed mostly of water ice with embedded dust particles.

Back to Basics

What is an asteroid?

• Asteroids are rocky objects that orbit the Sun, much smaller than planets.
• They are also called minor planets. As per NASA, 994,383 is the count for known asteroids, the remnants from the formation of the solar system over 4.6 billion years ago.
• Most such objects can be found in the asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9 million asteroids.
• The explanation for the concentration of asteroids in this belt comes from the formation of Jupiter, whose gravity brought an end to the formation of any planetary bodies in this region, as a result of which the smaller bodies kept colliding with each other, fragmenting into asteroids.
• Other than those found in the main asteroid belt, asteroids can be classified into trojans, which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.
• The third classification of asteroids can be as Near-Earth Asteroids (NEA), which have orbits that pass close by the Earth. Those that cross the Earth’s orbit are called Earth-crossers.
• More than 10,000 such asteroids are known, out of which over 1,400 are classified as potentially hazardous asteroids (PHAs).

Why do scientists track asteroids?

• Scientists study them to look for information about the formation and history of planets and the sun, since asteroids were formed at the same time as other objects in the solar system. 
• Another reason for tracking them is to look for asteroids that might be potentially hazardous.

When do asteroids become dangerous?

• According to The Planetary Society, there are estimated to be around 1 billion asteroids having a diameter greater than 1 metre.
• The objects that can cause significant damage upon impacting are larger than 30 metres. Every year, about 30 small asteroids hit the Earth, but do not cause any major damage on the ground.
• According to NASA, “Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid’s potential to make threatening close approaches to the Earth. Specifically, all asteroids with a minimum orbit intersection distance (MOID) of 0.05 au or less are considered PHAs.”
• 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 (bigger than a small football stadium) – which, according to the space agency, are of “the greatest concern” due to the level of devastation their impact is capable of causing.
• However, it is important to note that no asteroid larger than 140 metre has a “significant” chance of hitting the Earth for the next 100 years.

How can asteroids be deflected?

• Over the years, scientists have suggested different ways to ward off such threats, such as blowing up the asteroid before it reaches the Earth, or deflecting it off its Earth-bound course by hitting it with a spacecraft.
• The most drastic measure undertaken so far is the Asteroid Impact and Deflection Assessment (AIDA), which includes NASA’s Double Asteroid Redirection Test (DART) mission and the European Space Agency’s (ESA) Hera.
• The mission’s target is Didymos, a binary near-Earth asteroid, one of whose bodies is of the size that could pose a significant threat to Earth.

How are asteroids named?

• They are named by the International Astronomical Union (IAU).
• NASA notes that the IAU’s Committee on Small Body Nomenclature is less strict when it comes to naming asteroids than other IAU naming committees.
• Asteroids are also named for places and a variety of other things and the IAU discourages naming asteroids for pets.

Source: Indian Express