The sky on the holiday weekend

You’re on a blanket or a lounge chair, waiting for the fireworks. Twilight is deepening. The stars are beginning to emerge. It’s 9:30 this weekend, either the Fourth of July or Saturday the 6th. You’ve been chatting with family or friends, but perhaps out of impatience you look around the sky.

Multiply this scenario 40 million times over, and that’s the scene each year on this date. It’s when more people watch the night sky than any other time by far.

I know that most people don’t care very much about astronomy – certainly not enough ever to bother with a star chart. But if something cool is happening right over our heads, of course we’ll take a look. So let’s gaze around the sky this weekend, just before the show begins.

So happens, on this weekend in 2014, 2015 and 2016 there will be true celestial fireworks to rival those that we humans create. The coming years will bring a rivetingly close don’t-miss conjunction between Venus and Jupiter. Another Independence Day weekend, Mars and the Moon will grab the spotlight. Stuff like that.

This time around, we get something more subtle: not dazzling, but still worthwhile. It’s a celestial version of the old red-white-and-blue.

Here’s what you do. First, just after 9 p.m. or so, look lowish down toward where the Sun set. Do you see any star there in the bright twilight? It’s Venus, beginning its visibility window of 2013.

After 9:15, face that fading glow of the sunset and point your left hand straight out to your left. Now look in that direction, the southwest, which is at right angles to the sunset. One-third of the way up the sky from the horizon float two bright (not brilliant) stars. The rightmost one is blue. This is Spica, Virgo’s main star. To its upper left hovers the planet Saturn, which is white. Now look far to their left and you’ll come to a red star. It’s the same lowish height as Saturn and Spica. This is the famous Antares: a red supergiant, one of the largest stars in our galaxy. (It’s actually orange, but it’s not wrong to call it “reddish.”) It’s the alpha star of Scorpius. Red, white and blue.

Got more time as the darkness deepens? Check out the overhead sky. Far above Saturn and Spica floats the very brightest overhead object: Arcturus. The Big Dipper’s handle arcs in its direction. If you’re with children, ask them to try to match the color of Arcturus with one of those previous stars. Do they see Arcturus to be more blue, white or reddish? They’ll find this fun.

It’s orange. Then tell them that stars come in every color except for one. Ask them to guess the only color never seen in stars. Some kid might cleverly say “black!” but she’d be wrong; there are indeed black dwarf stars. There are also brown and yellow ones. The answer is: green. No green stars in the universe.

It’s fun stuff to do before explosions bring us back to Earth.

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