Sunday 7 July 2013

Asteroid 2013 NJ4 makes a close pass to the Earth.

Asteroid 2013 NJ4 passed the Earth at a distance of 1 512 000 km  (3.9 times as far away as the moon) at about 4.50 pm on Sunday 7 July 20. It is an Apollo group asteroid, meaning that it spends most of its time outside of the Earth's orbit, but it closer to the Sun than we are at the innermost point. In the case of 2013 NJ4, which has a less eccentric orbit than most such objects, each orbit takes 437 days and takes it from 0.9 AU (i.e. 90% of the distance at which the Earth orbit's the Sun) to 1.35 AU, still inside the orbit of Mars. This means that close encounters between the Earth and 2013 NJ4 are not uncommon, the next will be in January 2014, but since the asteroid is only 15 m across it is not particularly threatening; it is too small to survive the journey through the atmosphere if it did hit us, so only scattered pieces, if anything, would reach the ground. The name 2013 NJ4 indicates that this was the 109th object discovered in the first two weeks of July.

The orbit of 2013 NJ4. Image created using the JPL Small Body Database Browser.

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