ASTEROID APHOPHIS-A CLOSE CALL TO THE EARTH IN 2029

It is astronomy’s most notorious asteroid. In less than five years, Apophis - the “God of Chaos” - will come very close to the Earth but it will not hit.

When first discovered in 2004, initial orbital calculations for Asteroid 99942 Apophis put Earth in a collision “danger zone” during its 2029 and 2036 passes. By Dec 27 2004 calculations indicated that it has a probability of 2.7% to hit the earth in its 2029 pass. The asteroid set a record when it was upgraded to risk level number 4 on the Torino impact scale, which is the highest rating given to any asteroid on that scale.  

However, additional observations have eliminated the possibility of an impact. Till Aug 2006 a small possibility of it hitting the earth remained which kept at a risk level of 1 on the Torino scale but that was later brought down to zero.   

Apophis is a clump of rocks about 350 metres across. The mass of the asteroid is about 4*10⁷ tons at an assumed density of 2.6 gm/cm³. It was measured to be traveling at a speed of 30.70 Km/Sec. On an average, an asteroid of this size impacts Earth every 80,000 years.  

It packs a kinetic energy equivalent to 1200 Megatons of TNT. That is about 80,000 times the power unleashed by the Hiroshima Atom Bomb. Any such impact could be extremely dangerous to an area of thousands of square kilometres and it would create a 5.1 kilometre crater. However, it would leave no lasting impact on Earth. If it hits the sea then it would cause Tsunamis in the surrounding areas.  

But additional observations and radar ranging have since considerably refined its orbital projections.

We now know that, on April 13, 2029, it will miss Earth by 32,000 kilometres. That would be the closest approach to earth by Aphophis. It would be the closes asteroid to the Earth of that size to be ever recorded. The closest approach would be visible from Europe, Africa and Western Asia when it can be seen as a 3.1 magnitude object and is visible to the naked eye.  

Because of its close approach to the earth, tidal forces are likely to alter Aphophis’s rotational axis. The earth can therefore also alter the orbit of Aphophis.

Calculations of the Jet Propulsions laboratory, California indicate that there is no risk of it hitting the earth for a further 100 years. This laboratory was founded by Caltech but is now under NASA.

The geostationary satellites that power the GPS on our mobiles are at a distance of 35,800km from us.  So, cosmically speaking, Apophis is still going to be a very close call.

The European Space Agency (ESA) wants to take a good look at it as it catapults by.