Midsummer has passed (for the northern hemisphere), though the hottest weather may be yet to come. June 28 saw the latest sunset, for latitude 40° north. Our page on “latest and earliest sunrise and sunset” explains why these events do not coincide with the June 21 solstice, and how their dates vary with latitude.
And after this late sunset, as the sky at last begins to darken, you can see through Earth’s atmosphere to our two neighbor planets, Venus and Mars.
See the end note about enlarging illustrations.
The arrows through the planets show their movement over five days. They’ve been getting closer together; Venus seems trying to overtake Mars – but won’t quite succeed. On July 1 the angular distance between them will reach a minimum (3.6°) – an event called an appulse, or closest approach. Usually when a moving body passes another, or a star, there are three moments: the appulse, the conjunction in right ascension, and the conjunction in ecliptic longitude. But this time there is no conjunction, no moment when Venus becomes exactly south of Mars by either measure.
The reason is made clear by this space view, which shows the planets’ paths in July, and the sightline from Earth past Venus to Mars on July 1.
You can also see in the charts for Venus and Mars, on pages 109 and 114 of Astronomical Calendar 2023, how Venus’s apparent path goes into a retrograde loop in July, while Mars keeps on in a straight line, against the background of the stars of Leo.
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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image” or “Open image in new tab”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
Last night, June 30 – July 1, was the first clear night here in San Francisco in weeks! I saw Venus, Mars, and Regulus, the Moon near Antares, and lots of stars. Before dawn this morning I observed Saturn, Neptune, Jupiter, and Uranus, and stars that we’ll be seeing in the evening sky during the autumn. It was the first time I’ve seen Uranus during his current apparition, and also Aldebaran and the brightest Hyades for the first time.