Archive for June 16, 2022

06/16/2022 – Ephemeris – Mercury’s poor showing in the morning sky at greatest elongation

June 16, 2022 Comments off

This is Ephemeris for Thursday, June 16th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 2 days past full, will rise at 12:17 tomorrow morning.

The planet Mercury has its greatest elongation to the west of the Sun around 11 this morning. That’s astronomer talk. It will be at its greatest angular separation west of the Sun. That angle will be 23 degrees. Being west of the Sun, it will rise before the Sun, and will be seen in the east. That makes perfect sense, but sounds weird. Not all Mercury greatest elongations are created equal, and being inhabitants of the Northern Hemisphere, we get the short end of the orbit. Mercury has the most elliptical orbit of any planet, since Pluto was kicked out of the planet club. That and Earth’s own axial tilt works against us. This is a poor elongation for us since Mercury is more to the side than above the Sun in the morning.

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.


Mercury greatest elongation diagram

Mercury at greatest western elongation this morning, June 16, 2022. Note that Mercury is more to the right of the Sun, than above it. This is a poor elongation for us. Created using Stellarium.

Mercury greatest western elongation in October 2022

Mercury at greatest western elongation, October 8, 2022. Note that Mercury is more above the Sun, than to the right of it. This will be a good elongation for us. But also note Mercury’s orbit. Mercury is near its perihelion point, its closest to the Sun. Southern Hemisphere observer good elongations feature Mercury near its aphelion, it’s farthest from the Sun. Those southerners get a much better look at Mercury than we do. Created using Stellarium.