Archive

Archive for November 20, 2020

11/20/2020 – Ephemeris – Martian Trojan asteroid may have come from our Moon

November 20, 2020 Comments off

This is Ephemeris for Friday, November 20th. Today the Sun will be up for 9 hours and 22 minutes, setting at 5:09, and it will rise tomorrow at 7:48. The Moon, 1 day before first quarter, will set at 10:39 this evening.

The way gravity works there are several gravitational sweet spots called Lagrangian points between orbital bodies. Two of those points, 60 degrees ahead of and behind a planet in its orbit, are called L4 and L5. Bodies at these points are called Trojan asteroids. Because the first ones found in Jupiter’s orbit were named after warriors of the Trojan War. What was discovered recently was that one of the planet Mars’ L5 Trojans is not like the others. It has a different composition as analyzed by a spectrograph. It reflects light like the Earth’s Moon, while the others appear to have come from Mars itself. Perhaps an ejected piece of the Moon made it out to Mars orbit. We know small meteoroids can make it planet to planet, maybe huge chunks can make it too.

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

Addendum

Martian Trojan asteroids

Mars and its Trojan asteroids including 101429 the asteroid that is spectroscopicly like the Moon. The other Trojans appear to have come from Mars itself. I tend to be a stickler for image accuracy: The Mars image is upside down and reversed, while the rest of the diagram is essentially correct other than being way out of scale. Credit Armagh Observatory and Planetarium (AOP) in Northern Ireland.