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Sunday, April 18, 2021

Explained: Why asteroid Apophis will not hit Earth for at least 100 years

Named after the ancient Egyptian god of chaos and darkness, asteroid Apophis was discovered in 2004, after which NASA had said that it was one of the asteroids that posed the greatest threat to Earth.

By: Explained Desk | New Delhi |
Updated: March 30, 2021 7:20:53 am
Apophis measures 340 metres across– comparable to the size of the huge ship that blocked the Suez Canal.

The USA’s NASA space agency has ruled out the possibility of the dreaded asteroid Apophis causing any damage to the Earth for the next 100 years.

Named after the ancient Egyptian god of chaos and darkness, it was discovered in 2004, after which NASA had said that it was one of the asteroids that posed the greatest threat to Earth.

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Apophis measures 340 metres across– comparable to the size of the huge ship that has currently blocked the Suez Canal. (That ship, the Ever Given, is 400m in length, 200m width)

What NASA has said about Apophis

Apophis was predicted to come threateningly close to us in the years 2029 and 2036, but NASA later ruled these events out. There were still fears about a possible collision in 2068, however.

This year, the asteroid flew past Earth on March 5, coming within 17 million km of our planet. During this approach, scientists used radar observations to study in detail the asteroid’s orbit around the sun.

In order to track Apophis’ motion, astronomers used the 70-metre radio antenna at the Deep Space Network’s Goldstone Deep Space Communications Complex near Barstow, California. They also used the 100-metre Green Bank Telescope in West Virginia which showed imaging of Apophis. The two systems were used together in a “bistatic” experiment that doubled the strength of the received signal.

Based on these findings, they were able to rule out any impact risk to Earth from Apophis in 2068 and long after.

“A 2068 impact is not in the realm of possibility any more, and our calculations don’t show any impact risk for at least the next 100 years,” said of NASA’s Center for Near-Earth Object Studies (CNEOS) said in a statement Friday.

“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029. This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”

The “risk list” refers to the Sentry Impact Risk Table maintained by CNEOS, which includes all the asteroids with orbits close to Earth.

As said, the large asteroid will now approach Earth again in 2029, when it is expected to come as near as 32,000 km– only one-tenth of the distance between the Earth and the Moon.

That year, the asteroid would be visible to star gazers in Asia, Africa and parts of Europe, without the need to use binoculars or telescopes.

What are asteroids?

Asteroids are rocky objects that orbit the Sun, much smaller than planets. They are also called minor planets. According to NASA, 994,383 is the count of known asteroids, the remnants from the formation of the solar system over 4.6 billion years ago.

Asteroids are divided into three classes. First, those found in the main asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9 million asteroids.

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The second group is that of 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 is 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).

Apophis is categorised as a PHA.

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