Don’t miss the triangle in the sky

(Photo by Katelyn Fay)

(Photo by Katelyn Fay)

Tonight, or the first clear night, face south between 8:30 and 9 p.m. Rather low in that direction is a striking triangle: three bright stars. You can’t miss it. Rarely is astronomy this easy. You don’t even have to know which direction is south, because there’s no small bright triangle of stars anywhere else in the heavens.

The leftmost star is the brightest, and has an obvious orange color. This is the planet Mars. It came closest to us in May, and it’s still very bright. It will of course be the first planet that humans visit. It has the only surface with a reasonable temperature.

Mars comes near to us every 26 months. For about 12 of those, the “Red Planet” is bright and obvious, and we are still in that period. But it’s fading rapidly, and will keep dimming steadily throughout the fall and winter. When it comes back to glory in 2018, it will be simply dazzling. For now, don’t bother pointing a telescope its way; its disk is currently too small to show any detail. Just check it out with the naked eye – that’s plenty good enough.


To the right of Mars is another orange star. This one’s a real star: the famous Antares, the brightest star of Scorpius the scorpion. It may be the largest bright star in the heavens, though that honor probably belongs to Orion’s Betelgeuse. Legend has it that the hunter killed the scorpion, and the gods mercifully decided to keep them forever separated. Thus the two constellations are never visible at the same time; they’re on opposites sides of the firmament.

Every few years, a more refined measurement of star distances makes us think that Antares is the largest bright star. Fans of each distant sun have been cheering on their favorite supergiant for years. But at the moment, it seems that Betelgeuse is slightly bigger. Still, if you built a scale model in which our planet Earth is the period at the end of this sentence, then Antares would be a ball as tall as a 14-story building.

The final star in the triangle, the topmost one, is the planet Saturn. This is where to point your telescope. It is certainly among the five best celestial splendors. And since many people have telescopes of all sizes gathering dust and simply don’t know where to aim them, here’s where.

This year, the rings are angled in a wide-open position, farthest from edgewise. Their orientation is perfect. Saturn is glorious. The only trick is that to see all the juicy detail, like the inky-black separation between its wider B ring and its darker and narrower A ring, requires steady air.

Around here, steady air arrives when conditions are a bit hazy, meaning humid. As I write this, the forecast for Thursday through Sunday is for wonderfully crisp conditions, with dewpoints in the 40s or low 50s. That’s fabulous for seeing lots of stars, but usually causes twinkling and blurriness through telescopes. So before you bother lugging out the instrument, see if the stars are twinkling. If they are, don’t bother, because Saturn will be a blurry mess.

But don’t miss the triangle. Night after night, Mars speedily moves to the left against the background stars. This is its actual eastward orbital motion, at 15 miles per second. It’s now strikingly obvious, because in just a few nights it will stretch out the triangle like pizza cheese. Then this gorgeous in-your-face show will be over for keeps.


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