Home > Commercial space flight, Ephemeris Program, The Moon > 09/17/2021 – Ephemeris – The Moon has an atmosphere of sorts; Plus, I capture Inspiration 4 passing overhead

09/17/2021 – Ephemeris – The Moon has an atmosphere of sorts; Plus, I capture Inspiration 4 passing overhead

September 17, 2021

This is Ephemeris for Friday, September 17th. Today the Sun will be up for 12 hours and 24 minutes, setting at 7:49, and it will rise tomorrow at 7:25. The Moon, 3 days before full, will set at 4:24 tomorrow morning.

Jupiter, tonight, will be above the Moon. Everyone knows that the Moon is airless, that is has no atmosphere. That is not strictly true. Apollo astronauts saw glows and crepuscular rays in the direction of the Sun before its rising an after it set as they orbited the Moon. In 2013 NASA sent an orbiter spacecraft named LADEE to the Moon to investigate. LADEE stands for Lunar Atmosphere and Dust Environment Explorer. It orbited low over the Moon’s equator. The atmosphere of the Moon consists of some gasses like sodium, neon, argon and helium plus dust electrostatically charged by the Sun’s x-ray and ultraviolet emissions and sent aloft, up to many kilometers. The dust will fall back down, but the gasses will be dissipated by the solar wind. It’s very tenuous.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.


Jupiter, Saturn and the Moon tonight at 9 pm tonight, September 17, 2021. Jupiter will be moving to be directly below Jupiter by one in the morning. Created using Stellarium.

Apollo 17 twilight ray sketches

Apollo 17 twilight ray sketches. Credit: NASA/Apollo 17 Astronauts.


Artist’s depiction of LADEE in orbit of the Moon. Courtesy NASA.

Inspiration 4 spacecraft caught flying over Northern Michigan

Inspiration 4 spacecraft passing through Hercules

The thin vertical streak on the left side of the image is the Inspiration 4 spacecraft against the stars of Hercules in a 15 second exposure with a Canon Rebel T5 camera, f/3.5, ISO 6400, 18 mm fl. The famous Keystone of Hercules asterism is to the upper right of center. It’s a bit out of focus due to my problem seeing the screen at a high angle. (Getting old). It was quite dim, so I actually couldn’t see it in the moonlight. Credit: mine.

I was guided to the time and place in the sky by heavens-above.com

%d bloggers like this: