Bob Moler's Ephemeris Blog

Ephemeris for Monday, December 17th. The Sun will rise at 8:14. It’ll be up for 8 hours and 48 minutes, setting at 5:03. The Moon, 2 days past first quarter, will set at 3:15 tomorrow morning. |

Newton’s law of gravitation allows for some gravitational equilibrium points around two bodies that orbit each other. Discovered in th 18th century by Leonhard Euler and Joseph-Louis Lagrange these are known as Lagrange or L points. There are five. L1 is between the two bodies. The L1 point between the Earth and Sun is a million miles sun-ward of the Earth, where we station solar observation satellites. L2 is a million miles in the other direction, where there are astronomy satellites looking anywhere but the Sun. The James Webb telescope will join them there. L3 is point on the other side of the Sun, for which no use has yet been found. L4 and L5 are 60 degrees ahead of and behind the Earth’s position in its orbit. These are quite stable. Jupiter has thousands of asteroids in its L4 and L5 locations called Trojan asteroids.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The 5 Lagrange points about two bodies M1 and M2 orbiting each other. Credit Georgia State University.