There may be eight planets and five dwarf planets in the solar system, but the terrestrial (rocky) planets of the inner solar system are where it’s at.
The closest four planets to the sun—Mercury, Venus, Earth and Mars—are also relatively close to each other and often shine brightly in each other’s night skies. If you’ve been watching the planets this year you’ll know that Venus and Mars have been visible the entire time.
Just occasionally all the rocky planets shine brightly together—and that’s exactly what happens this week as tiny, fast-moving Mercury joins the duo just as the planetary party is coming to an end.
From around Wednesday, July 19, 2023 it will be possible to watch Mercury in the post-sunset sky, rising each night to take its place with Venus and Mars.
You’ll need to look northwest, preferably from somewhere with a clear view of the horizon. A pair of binoculars will be helpful for finding Mercury.
To see the fourth rocky planet, of course, just look around you!
However, you’ve not got long to take in the sight of the four inner planets because just five nights later Venus will sink into the sun’s glare and disappear from sight. Mars won’t be far behind it, and besides, Mercury won’t stick around beyond early next week.
This is your last chance to see the inner solar system in one minute.
Here’s what you’ll see across those five nights:
Wednesday, July 19: Mercury Joins Venus, Mars And The Moon
Mercury will be to the lower right of a 5% crescent moon, with bright Venus to to the left and Mars to its upper-right (in between Mars and Venus will be the star Regulus in Leo).
Thursday, July 20: Mercury Rises, Venus Sinks and the Moon Sits Near Mars
Go look west tonight and you’ll see Mercury a little higher in the night sky, Venus a little lower, and a now 10% illuminated crescent moon next to Mars.
Friday, July 21: Mars and Venus Align With The Crescent Moon as Mercury Rises
Tonight there’s a beautiful view of Mars and Venus aligning with a 15% lit crescent moon, with Mercury to the right of Venus, still low on the horizon, and about as high as it’s ever going to get in it’s brief apparition.
Saturday, July 22: Venus on the Cusp as Mercury Peaks
It would be wise to come outside slightly earlier tonight to look for the planets in a brighter sky, because Venus is now on the cusp of disappearing altogether.
Sunday, July 23: Last Call for Inner Solar System Views
Here’s your last chance to see the three other rocky planets in the night sky, as Venus continues to sink out of view, now visible only in early twilight. However, you should still be able to see Mercury, which will be slightly closer to Venus tonight, and Mars above.