Tuesday, June 21, will bring the solstice, peak of summer for our northern hemisphere. Usually the hottest weather comes later, but there are pre-solstice heat waves in Spain and France.
June 21 is also, this year, something of a hinge date for other sky events.
See the end note about enlarging illustrations. Arrows through the moving bodies, including the Sun, show their motion from 2 days before to 2 days later, in relation to the starry background.
From the Sun, it’s 90 degrees – a quarter of the way around the celestial sphere – to the point marked “Earth’s direction of travel.” This point now coincides with the node were ecliptic and celestial equator cross, the Sun being at the solstice point, the farthest north on the ecliptic.
The instant of the solstice – when the Sun is exactly farthest north – is 9:17 by Universal Time, so only half an hour before the time of our picture.
It happens that the Moon is also 90° west of the Sun: at last quarter, crossing inward over our orbit ahead of us. The last-quarter Moon always acts as a signpost, showing us where we will be in only about three and a half hours. The last-quarter instant is 3:11 by Universal Time, which by North American clocks is four or more hours earlier and thus back in the calendar day of June 20.
And a third happening on this June 21 is that Mars is at the perihelion of its orbit, the closest in toward the Sun.
This space view, extracted from the globe picture on page 113 of our online Astronomical Calendar 2022, shows how Mars’s quite elliptical orbit comes closest to us where it is in the Aquarius direction.
The distance from Sun to Earth is called the “astronomical unit,” and Mars at its perihelion is 1.38 AU from the Sun. You can also see that our present view toward Mars is to the “right” (west) of the Sun, in the morning sky. We are hurrying after Mars, and won’t overtake it at opposition till December 8.
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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.
This weblog maintains its right to be about astronomy or anything under the sun.
I can’t get enough of these types of posts. Thinking about all of the angles and planes in our solar system is endlessly fascinating and I sincerely appreciate the time and effort you spend in sharing the interesting configurations with us. Thank you!
once again incisive, and accessible. thanks for the years that you have provided this information.