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Normally, we think of Earth as the Blue Planet, but there are two others: Uranus and Neptune. Uranus has more of a turquoise hue, while Neptune looks like a giant blueberry. Our planet's color comes from sunlight reflected from its vast oceans. The two outermost planets look that way because methane gas in their atmospheres absorbs sunlight's warmer colors and reflects back blue.
Mars glows unequivocally red from — of all things — rust. Its rocks are rich in iron, which readily combined with oxygen from the breakdown of water (H2O = hydrogen + oxygen) by sunlight in the planet's early atmosphere to form iron oxide. On Earth, oxygen from plants joins forces with water to slowly rust our cars and trucks.
Starting later this week and continuing through early August, the rusty Red Planet will glide past gassy, blue Uranus. Most lovers of the night sky have never seen Uranus even though it's four times as big as the Earth. That's only because it's so far away — 1.85 billion miles (3 billion kilometers) on July 28. From a dark, rural sky, it looks like a very faint star without optical aid. Binoculars show it well enough, but its color and shape are only visible in a telescope magnifying around 100x.
Mars is about 7 1/2 times smaller than the seventh planet but currently 17 times closer, so it appears larger and considerably brighter. The two planets meet up later this week, with Mars passing the remote planet over the course of several nights. The pair first appears low in the eastern sky around 1 a.m. local time, but you'll see them best just before dawn, when they're highest in the southeastern sky.
You can kill two astronomical events with one stone this weekend. At the same time Mars and Uranus approach conjunction, the annual Southern Delta Aquariid meteor shower peaks. This is a minor shower, but at least we'll have moonless skies for it. That won't be true for the upcoming August Perseids which will compete with a nearly Full Moon.
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Shower members will fly out the sky from a spot called the radiant located near the star Delta in Aquarius, hence the name. From a dark location you'll see up to 15 meteors an hour, all pointing back to the south-southeastern sky a little more than a fist to the left of Saturn. Best viewing will be from midnight Friday night, July 29, through the early morning of Saturday, July 30. The radiant reaches its highest point in the southern sky around 3 a.m. local time.
Meteor showers are easy to observe and a lot of fun. Like me you've probably noticed that they rarely live up to the forecast number per hour because most observers have to deal with varying degrees of light pollution. But don't let that stop you. Spread out in a reclining chair and simply look up. You'll see meteors, satellites, the Milky Way, planets and maybe even a thing or two you can't explain.
"Astro" Bob King is a freelance writer for the Duluth News Tribune.
