4.8 km wide asteroid to flyby Earth at 57.2 LD

A 4.8 km (2.98 miles) wide asteroid named 5143 Heracles will make a close approach to Earth on November 28, 2016, passing 57.2 LD (21.9 million km / 13.6 million miles) from the surface. Heracles will safely flyby our planet at 23:29 UTC at a relative velocity of 27.38 km/s.

Heracles is a binary, Apollo-class near-Earth asteroid discovered on November 7, 1991 by Carolin S. Shoemaker at Palomar Observatory near Pauma Valley, California. 

It has a period of 2 years and 175 days.

Taylor, Nolan, and Howell at Arecibo Observatory, National Astronomy and Ionosphere Center made radar observations of Heracles from December 10 to 13, 2011, and found it is a binary system. 

The imaging suggest that the component diameters are 3.6 +/- 1.2 km (2.2 +/- 0.74 miles) for the primary and 0.6 +/- 0.3 km (0.37 +/- 0.18 miles) for the secondary. The orbital period appears to be between 14 and 17 hours with a separation of at least 4 km (2.48 miles). The team's report also noted that an orbital period between 40 and 57 hours with an implied separation of at least 11 km (6.83 miles) could not be ruled out, but would be inconsistent with their assumption of a synchronously rotating secondary body. 

5143 Heracles is named after the son of Zeus and Alcmene in Greek mythology. He was the greatest of the Greek heroes. In Rome and the modern West, he is known as Hercules.

Its next close approach will occur on November 18, 2021 at a nominal distance of 119.2 LD (45.7 million km / 28.4 million miles).

[ Ephemeris | Orbit Diagram | Orbital Elements | Physical Parameters | Discovery Circumstances | Close-Approach Data ]

As of November 26, 2016, there are 874 near-Earth asteroids with an estimated diameter of 1+ km (0.62+ miles) out of 15 234 known NEAs.

Featured image: Asteroid 5143 Heracles, November 29, 2016. Credit: NASA/JPL