An asteroid is going to fly past the Earth today at 2.24 pm IST, but simmer down for a beat, because it won't be knocking anyone dead. This space rock will fly past us as it follows an Earth-crossing orbit, which means it has a chance of colliding with the planet.
The asteroid, called 2017 AP4, is an example of what space scientists call "Near-Earth Asteroids" or "Near-Earth Objects" (NEOs). These are asteroids and comets that occasionally cut into Earth's orbit of the Sun as they cruise through the inner rings of the solar system.
It is expected to zip past us at close range at speeds of 27,000 kilometres per hour, is between 11-25 m wide in size and it will be 3,253,487 km from Earth. It was first observed on >4 January 2017, when it passed Earth without incident. Even if it had, it would not have caused any harm given its (relatively) small size, which would ensure it burns up into vapour in the Earth's atmosphere well before it gets a taste of Earth's surface.
2017 AP4 is classified as a member of the 'Apollo family of asteroids', according to the >Centre for NEO Studies. Like the other Apollos, 2017 AP4 follows a wide trajectory that takes it around within the Solar System. However, from time to time, its orbit intersects with that of Earth as the planet completes its cycle around the Sun.
Asteroids regularly make close approaches to Earth, and NASA creates alerts for each one of these objects. Sometimes several will even pass by in a single day " completely unnoticed by humanity.
However, neither NASA nor any other space agency has the means to protect the Earth from collisions other than to observe them from a distance and inform people well ahead of time.
A NEO is a comet, asteroid or any small Solar System body whose orbit brings it in close proximity with Earth. If a NEO's orbit crosses the Earth's, and the object is larger than 140 meters across, it is considered a potentially hazardous object (PHO). NASA tracks these NEOs and maintains a database.