Apophis Travel Time To Reach Earth:


Apophis Asteroid collision with Earth possibility


Sources: NASA | Planetary Society

Friday the 13th is supposed to be an unlucky day, the sort of day you trip on your shoe laces, or lose your wallet, or get bad news.

But maybe it's not so bad after all. Consider this: On April the 13th, (Friday the 13th) 2029, millions of people are going to go outside, look up at the sky, and marvel at our good luck. A point of light will be gliding across the sky, faster than many satellites, brighter than most of our visible stars. What's so lucky about that? It's asteroid 99942 Apophis (2004 MN4), not hitting the Earth. For a short while astronomers thought that it might. On Christmas Eve of 2004, Paul Chodas, Steve Chesley and Don Yeomans at NASA's Near Earth Object Program office calculated a one-in-60 chance that asteroid 99942 Apophis (2004 MN4) would be hitting the Earth on April 13th, 2029. Astronomically speaking, those are incredibly bad odds. That's a higher probability ratio than getting in a car accident on your local highway. Luckily since 2004, NASA scientists have now changed their numbers. Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth on April 13, 2029. As of 2009, however, additional observations of Apophis have now ruled out any possibility of an impact in 2029 at all. But, boy is it going to be close!

In the above diagram, what you see is the most likely position of Apophis (2004 MN4) at the end of the blue line in the proximity of the Earth and the orbit of the Moon on April 13, 2029. However, since the asteroid's position in space is not perfectly known at that time; the white dots at right angles to the blue line are possible alternate positions of the asteroid. Neither the nominal position of the asteroid, nor any of its possible alternative positions, touches the Earth, thus indicating that an asteroid impact of Apophis and Earth in 2029 is completely ruled out.

Nevertheless, the asteroid is still expected to make a record-setting -- but harmless -- close approach to Earth on the date of Friday, April 13, 2029. At this time, it will come no closer than 18,300 miles above the Earth's surface. This is within the distance of Earth's geosynchronous satellites. However, because Apophis will pass interior to the positions of these satellites in a plane inclined at 40 degrees to the Earth's equator at its closest approach, and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it doesn't threaten the satellites in that heavily populated region. But again, that's really close and the primary reason why so many end of the world predictions are being given about a doomsday asteroid impact.

Arecibo Observatory, World's Largest Radio Telescope

To put things in perspective, let's take a look at the dimensions of this asteroid. Apophis is about 320 meters wide. This is approximately the size of two-and-a-half football fields. "That's big enough to punch a hole through the Earth's atmosphere", said Chodas, "devastating a region the size of, say, the state of Texas, if it hit land, or causing widespread tsunamis if it hit the ocean." So, the reason for concern is real.

Coincidentally, the Arecibo Observatory in Arecibo, Puerto Rico, which is home to the world's largest and most powerful radio telescope (astronomical radar facility) and currently being used to monitor the near Earth movements of celestial objects is just about the same size as asteroid Apophis (aka, 99942 Apophis, 2004 MN4).

Pathway of the Apophis asteroid as it nears the Earth and Moon orbits