10/25/2021 – Ephemeris – Mercury is at its greatest separation west of the Sun of the season

This is Bob Moler with Ephemeris for Monday, October 25th. Today the Sun will be up for 10 hours and 29 minutes, setting at 6:41, and it will rise tomorrow at 8:13. The Moon, 3 days before last quarter, will rise at 9:38 this evening.

This morning at 12:59 am, the planet Mercury reached its greatest western elongation from the Sun. It reached an angle of 18.4 degrees west of the Sun. It will be visible for most of the 7 am hour low in the east southeastern sky. Mercury will be visible to the naked-eye for the next week or 10 days. The planet has quite an elliptical orbit. And it happens that in our favorable appearances of Mercury on fall mornings and spring evenings, we are seeing Mercury in the same part of its orbit. Which is near its perihelion, the closest part of its orbit of the Sun. Observers in the Southern Hemisphere see Mercury’s favorable elongations near aphelion, its farthest from the Sun, of around 28 degrees separation from Earth’s viewpoint.

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

Addendum

Mercury, a day after greatest western elongation at 7:54 am, or 20 minutes before sunrise tomorrow morning, October 26, 2021. Also shown is its orbit, if we could see it. Mercury is virtually in the same position this morning. Created using Stellarium.