Apophis is the name of a near-Earth asteroid, which might have a close encounter with earth in 2029. Apophis Asteroid would pass through a gravitational keyhole, which is about half a mile wide, which would attracts the asteroid closer to earth and set us up for an impact on April 13, 2036. Apophis broke the record for the highest level on the Torino Scale, by being placed at a level 4 for only a short time.
Comets vs. Asteroids
The biggest known comet is 70 km large. Even if you add 50% it is still tiny compared to asteroids. Comets cause trouble by their extremely high speed, but they are also extremely fragile. Most of them will burn up during the entry into the atmosphere of Earth. The damages from comets would be rather like that:
- The direct damage by the fireball
- The radiation damage by the fireball (fireball is hot, and hot things emit thermal radiation)
- The ejecta (like shrapnel) of the impact, reaching you at supersonic speed. Imagine a wave of hot stones rolling over you and traveling up to once around the world.
- The seismic shockwaves = Earthquake. Travel at the speed of sound inside Earth, and takes a moment.
- The air blast which travels at the speed of sound. Once you hear the impact, its other effects would have already reached you.
ISON comet is another amazing object which is supposed to have a near sun encounter. At its peak when the comet reaches its perihelion on 28 November, It may briefly become brighter than the full Moon. But before that happens, ISON comet will achieve these milestones first. During August 2013, it should become bright enough to be visible through small telescopes or even binoculars, eventually becoming visible to the naked eye by late October. The comet will then pass through the constellation Leo, passing near Leo's brightest star Regulus and then passing near Mars in the night sky, and these brighter objects might make the comet easier to locate. In November, when the comet is brighter, it will sweep another bright star in our sky, Spica in the constellation Virgo, and another planet, Saturn. Around the time the comet reaches its perihelion on 28 November, it may become extremely bright it might probably reach a negative magnitude and briefly become brighter than the full Moon.
Apophis Asteroid is approximately 1,066 ft. (325 meters). Being a near-Earth object (NEO) means it is an object whose orbit brings it into proximity with the Earth. All NEOs have a closest approach to the Sun (perihelion) of less than 1.3 AU. They include a few thousand near-Earth asteroids (NEAs), near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the planet. NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose to the Earth, and active mitigations are being researched.