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What ever happened to the Earth destroying asteroid Apophis?

Astronomers were busy collecting pictures of the asteroid Apophis during its most recent flyby in early March. Later calculations enabled NASA scientists to declare on March 26, 2021, that Earth is safe from a collision with the moderately massive asteroid for at least the next 100 years. 

Radar scans at NASA's Goldstone Deep Space Communications Complex in California and the Green Bank Observatory in West Virginia have formally ruled out an impact in 2068, the only year out of the next 100 that previously suggested a minor danger. Earlier observations had ruled out impacts for the future flybys in 2029 and 2036.

In comparison to Earth's orbit, the orbit of the asteroid Apophis (pink) is shown (blue). The sun is represented by the yellow dot. Apophis orbits the sun in 323.6 days. Earth takes 365.3 days. As a result, this asteroid is a regular visitor to our region of space. Image courtesy of Phoenix7777/Wikimedia Commons.

Apophis is no longer on the Sentry Impact Risk Table, which is a list of objects that travel so close to Earth that astronomers have not yet ruled out a probable hit.

Apophis is a rather massive near-Earth asteroid (approximately 1,100 feet – or 335 metres – broad). It sprang to prominence in 2004 when first measurements revealed that it may collide with Earth around 2029. Despite the fact that it will reach frighteningly near to Earth in 2029, an attack has been ruled out. Apophis will pass Earth on Friday, April 13, 2029, at a notional distance of 19,662 miles (31,643 kilometres). In comparison, the average distance between the Earth and the Moon is around a quarter-million kilometres (380,000 km).

All eyes were on Apophis in early March, as the asteroid passed reasonably close to our planet (albeit not nearly as close as in 2029) on March 6. For nearly two weeks around the closest approach, the Goldstone Deep Space Communications Complex tracked the asteroid. Green Bank Telescope researchers conducted observations in collaboration with Goldstone because the utilisation of these two telescopes combined provides for clearer data. Because the two telescopes were in sync, Goldstone was broadcasting data while Green Bank was receiving, resulting in a bistatic experiment that twice the power of the received signal.

Further examination of the radar data gathered in early March should assist astronomers in determining the form of Apophis. Previous observations indicate that the asteroid is peanut-shaped – also known as bilobed, or having two lobes – which is a common form for near-Earth asteroids.

Furthermore, scientists want to learn more about the asteroid's rotation rate and spin state, which may reveal what consequences Apophis may experience during its extremely close approach in 2029. Apophis may experience asteroid quakes when it collides with Earth's gravitational field in 2029.

Apophis will also be studied by astronomers using NASA's NEOWISE infrared satellite telescope in April 2021. This is the same telescope that found Comet NEOWISE, 2020's favourite comet, which has since faded from view.

Astronomers in Hawaii recently investigated how Yarkovsky acceleration, or solar pushes, would alter Apophis' orbit. Acceleration — a change in an object's speed and direction across space – might assist prevent a collision in some cases. Studies of Yarkovsky acceleration in relation to asteroid Apophis indicate that this is the case. Previous predictions (performed in 2016) have all but eliminated the possibility of an impact in 2068. In 2016, the chances of an asteroid collision were viewed as vanishingly small, with just 1 in 150,000 odds of impact, or a 99.99933 per cent probability the asteroid would avoid the Earth.

The most current findings, which were originally presented in October 2020 and revised in early 2021, revealed a decreasing danger.

Apophis is deviating from its anticipated orbit by more than 500 feet (about 170 metres) every year. These observations are difficult to collect and assess. The asteroid's distance at the time of observation, composition, shape, and surface characteristics all have an impact on the conclusion.

Of course, Apophis is not the only near-Earth asteroid. Many minor asteroids racing close to Earth have been discovered and tracked by astronomers in recent years. For example, on September 24, 2020, asteroid 2020 SW passed even closer to us than our meteorological and television satellites, as well as other geostationary satellites, which circle our globe at a distance of 22,300 miles (35,900 km). Asteroid 2020 SW came within 7% of the Earth-moon distance. However, the diameter of asteroid 2020 SW is believed to be only 14 to 32 feet (4.5 to 10 metres). In comparison to the asteroid Apophis, this is rather modest.

Apophis, the asteroid, will pass by in 2029. Apophis' approach with Earth on April 13, 2029, will be quite near. Apophis will be around 10% of the Earth-moon distance at its closest in 2029. That's quite close for a 1,115-foot-wide (340-meter-wide) space rock!

Apophis will be on display for the general public and astronomers alike on Friday, April 13, 2029. Apophis will get so near that it will be visible to the naked eye; this is virtually never the case with asteroids. Apophis will initially be seen in the Southern Hemisphere, appearing as a speck of light travelling over Australia during this near approach, according to NASA. At its closest approach to Earth, it will be above the Atlantic Ocean. It will travel so quickly that it will span the Atlantic in an hour and will arrive in the United States in the late afternoon/early evening. According to calculations, Apophis will achieve a visual magnitude of 3.1 during this approach, which is equivalent to the stars in the Little Dipper. Apophis is anticipated to be visible to the naked eye from parts of Australia, Western Asia, Africa, and Europe by 2029.

The International Astronomical Union's Minor Planet Center has classed Apophis, like many other asteroids, as a potentially dangerous asteroid. That simply means it's an asteroid whose orbit gets it close to Earth on occasion and is large enough to cause "major regional damage" if it collides. According to a scan conducted by the NEOWISE satellite in 2012, there are 4,700 1,500 potentially dangerous asteroids with diameters more than 100 metres.

According to some predictions, an asteroid the size of Apophis will approach Earth every 80,000 years.

Bottom line: Early March observations of asteroid Apophis lead scientists to conclude that Apophis had no risk of colliding with Earth in the next 100 years.