Why is Apophis called a killer Asteroid?

On 19 June, 2004, astronomers at the Kitt Peak National Observatory in Arizona, USA noticed a 370-metre wide asteroid moving through the constellation of pisces. This asteroid was provisionally designated as 2004 MN4, and is both a Near Earth Object (NEO) that crosses the orbit of the Earth, and a Potentially Hazardous Asteroid (PHA), with a chance of striking the Earth in the distant future. At the time of discovery, the initial observations indicated that the asteroid had a small but scary chance of impacting the Earth during a close encounter on 13 April, 2029.

Once 2024 MN4 was confirmed by follow-up observations, it was formally dubbed 99942 Apophis, named after a giant serpent from Egyptian mythology representing chaos, evil and darkness. Further observations by optical telescopes and radar instruments revealed that the asteroid will not be striking the Earth in 2029 afterall. Even before the orbit was resolved, the Apophis got widespread coverage in the media, and earned the moniker of a ‘killer asteroid’ because of its initial perceived threat. An impact from the 370 metre wide asteroid was capable of wiping out a large city or causing regional devastation if it struck a populated area.

The orbit of apophis was refined by further observations in 2004, 2013 and 2021 eliminating the risk and confirming that the asteroid was not an impact threat for at least a century. The Torino Scale is a system to assess the potential hazard of asteroids or comets, and goes from 0 (No Risk) to 10 (Certain Collisions). Apophis was briefly assigned a Torino Scale rating of 4, which is the highest ever assigned to a space rock. A similar pattern has been observed on several other asteroids that were initially flagged as impact risks, but were subsequently cleared by follow-up observations.

2004 VD17 was given a Torino Scale rating of 2 due to a possible impact in 2032. This is a 500 metre wide asteroid. 2011 AG5 earned a Torino rating of 1, and is a 140 metre wide asteroid. 2007 VK184 is a 130 metre wide asteroid that was rated a 1 on the Torino scale. Based on follow-up observations by radar instruments and optical telescopes cleared the impact risks for all of these asteroids. These examples highlight how initial uncertainties in the orbits of asteroids can spark widespread concern, but subsequent precise tracking, often using radar instruments, tends to dispel the fears.

Apophis will approach closer than geostationary satellites in 2029. Media hype and the name, tied to the Egyptian chaos serpent have field apocalyptic speculation, including ridiculous, attention-grabbing content around 2029 marking the end of the world. The short answer is no, the world is not going to end in 2029. Decades of refined observations have debunked this doomsday scenario. In fact, the impact risk from Apophis had dropped to near-zero by the end of 2004 itself, the year in which it was discovered.

The observations conducted in 2013 and 2021 confirmed that the asteroid Apophis will safely miss the Earth in 2029, 2036 and even 2068. The Torino Scale rating for Apophis is now at 0, indicating that it poses no hazard to the Earth. Scientists, including those at NASA and ESA agree that the asteroid Apophis does not pose a threat to the planet. The path of the asteroid is now tracked so precisely, that scientists can measure the drift caused by the Yarkovsky effect, or energy from the Sun unevenly absorbed and reemitted by the asteroid.

Far from a catastrophe, 2029 offers a scientific bonanza. The close encounter will allow scientists to better understand the composition of near Earth asteroids, and how the shape, spin and orbit of the asteroid is modified by the close encounter with the Earth. The world will not end it 2029, instead its residents will get a front-row seat to a rare celestial event. During the flyby, Apophis will be visible to the naked eye in the skies of India, Europe and Africa.