Home > Ephemeris Program, The Moon > 10/19/2015 – Ephemeris – Where did the Moon come from?

10/19/2015 – Ephemeris – Where did the Moon come from?

October 19, 2015

Ephemeris for Monday, October 19th.  The Sun will rise at 8:03.  It’ll be up for 10 hours and 48 minutes, setting at 6:51.   The Moon, 1 day before first quarter, will set at 11:51 this evening.

Only two planets in the solar system have moons at least a quarter the size of the planet they orbit:  The Earth and Pluto.  The Moon is a bit more than a quarter the Earths diameter while Pluto’s moon Charon is half its size.  Probably in the early days of the solar system, some four and a half billion years ago collisions were rather common.  It is thought by many planetary scientists that a Mars sized protoplanet collided with the proto-earth with a glancing blow to rip off much of the Earth’s crust, thrust it into orbit where it coalesced into the Moon.  It seems that Pluto’s Charon may have been formed much the same way.  Some thing the varying axial tilts of the planets may have been caused the same way by smaller objects.

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


Collision spawning the Moon

The hypothetical collision of a Mars sized body with the young Earth. Credit: Joe Tucciarone via NASA

Breaking News

Robert Farquhar the man behind the ISEE-3 spacecraft, the first to hang out at the Earth-Sun L1 point between the Earth and the Sun back in 1978 passed away yesterday.  In 1982 he “stole” the spacecraft and through an amazing number of maneuvers using very little fuel managed to send it through the tail of Comet Gicobini-Zinner ahead of the fleet of spacecraft then aimed at Halley’s Comet.  Last year when the then renamed spacecraft ICE approached the Earth, he hatched a plan to return the spacecraft to its L1 position.  Unfortunately apparently there was not enough fuel pressure to complete the burns necessary for the task.  I’ll have a program on Robert Farquhar next Monday.

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