On March 20 the Sun will return to the northern half of the sky.
The instant when the vast star’s center crosses the celestial equator is just after 3 by Universal Time, which is back in March 19 by clocks in America. Here is the scene for an American location on the evening near the equinox.
See the end note about enlarging illustrations. Arrows through the moving bodies show their movement (against the starry background) from 2 days earlier to 2 days later. Moon and Sun are exaggerated 2 times in size. Broad arrows on the celestial equator show how much the whole sky will appear to rotate in one hour, therefore what is going to rise and set.
The picture is worth enlarging, being somewhat dense because it embraces half the horizon and packs a lot of information.
The moving point we call the “anti-Sun” is opposite to the Sun (180° from it), so one is rising as the other sets, and they are respectively at the September and March equinox points: the descending and ascending nodes of the ecliptic through the celestial equator. And half way (90°) between them, where the Sun will be at the June solstice, is the antapex of Earth’s way: the direction from which we are traveling at this moment in our orbit. The Moon passed this point when it was at its last-quarter phase, crossing our orbit behind us.
How equinoxes and solstice come about is made dynamically clear in the “Sun and Seasons” section on pages 85-87 of Astronomical Calendar 2024.
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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.
Sometimes I make improvements or corrections to a post after publishing it. If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version. Or you can click ‘Refresh’ to get the latest version.