Jupiter king, Venus queen of summer sky

Welcome to summer! The longest day of the year in the Northern Hemisphere will occur on June 21. Summer begins at the solstice at 5:07 a.m. CDT on that date.

The gas giant planet Jupiter will be the king of the night sky for most of the summer. Jupiter is about 11 times the diameter of Earth and has 63 known moons, some of them a bit in dispute. The last few discovered are extremely difficult to image and, compared to the diameter of the planet, are extremely small.

Amateurs love to see Jupiter in their telescopes because Jupiter rotates on its axis in about 10.5 hours and the conscientious observer can see much of its surface atmosphere across a single night. Jupiter has a very large ‘hurricane’ floating in its clouds — the Great Red Spot. The Great Red Spot could contain the diameter of the Earth easily.

I have been observing the Great Red Spot since I made my first telescope at age 14. Then, it was much brighter and more distinct at its borders than it is now. Many Jupiter experts believe the spot is fading and, as far as I can tell, they are correct. All amateurs with good mounts and even a small telescope can see the four moons that Galileo saw 400 years ago. The moons rotate around Jupiter and I have seen them disappear behind the planet, pass in front of it, and I have seen moons leave a shadow on the upper atmosphere of Jupiter when the moon lies between the Sun and the planet. Within that shadow, there would be a total eclipse of the Sun if there were any Jovians to observe it (very unlikely).

If Jupiter is the king of the night sky, then certainly Venus is the queen of the night sky. She can be found in the western sky shortly after sunset all month long. She is about the size of Earth but closer to the Sun than we are, so she is very hot and her surface is covered with volcanoes. She is very bright because her atmosphere is very white, being composed of carbon dioxide and sulfuric acid droplets. Right now, she is about five-eighths-full. She has phases like our moon, and Galileo is the first observer to observe this and record it in his journal.

Tiny Mercury will be visible all month with its clarity improving as the month goes on. Look for it with binoculars — it will appear low to the horizon in the northwest part of the sky after sunset. It will appear star-like and, unless you have a telescope of about six inches or larger, it is difficult to see it as anything but a star. I first saw Mercury with that first telescope I built. I can remember I had to haul the ‘scope up onto the roof of a house to see it. This was the only way I could avoid trees and other houses in my neighborhood because, unless I got above ground level, the view would have been blocked. Mercury, too, has phases, but just resolving the planet into a tiny disk is challenge enough.

This summer, we will have a march of the planets across the night sky. I have mentioned Jupiter and Venus, but Jupiter will be followed by Saturn and then Mars. Mars will be viewed by thousands of amateurs in August and September because this year Mars is closer to Earth and, hence, bigger in an amateur ‘scope. I have never gotten a good image of Mars, but this year I have a nice little planetary camera that is made to image the planets. If I get a good image of Mars, I will share it with you.

As summer moves on, the Milky Way will show itself as our planet lines up with the center of our galaxy. I will be describing many things in the Milky Way as future columns are written this summer.

Put on the bug killer and get out for the free show under the stars. Clear skies!

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