Thursday, March 11, 2010

Delusions of Grandeur

I love that the naked-eye planets have unique colors. It's true that some beginning stargazers have actually accused me of being “delusional” when I’ve attempted to point out to them color differences among various planets and stars. And in the interest of full disclosure, I suppose I should mention that I’m pretty sensitive to the shades and subtleties of color, and am fully prepared to vigorously debate the relative merits of cornflower and periwinkle.

But three of the five naked-eye planets are visible in the night sky now, so you can put my claim to the test yourself.

Star maps created with Your Sky

Right after sunset, about one fist-width above the western horizon, look for the bright beacon of our neighboring planet Venus. (Never look directly at the Sun!) A fist-width is your fist held at arm’s length against the sky and measured across the knuckles. Venus is the third brightest celestial object in Earth’s sky, after the Sun and the Moon, and it blazes with a bluish-white hue.

About a half-hour after sunset, face east-southeast and look for bright planet Mars. It’s shining just below Castor and Pollux, the namesake stars of Gemini the Twins. You can also find it by drawing an imaginary line from Sirius, the brightest star in the sky, to Procyon, the bright star northeast of Sirius (that is, a little above it and to the left). Keep going past Procyon, a little less than the distance between Sirius and Procyon, and look for a reddish or orange-colored "star." It appears distinctively copper to me. This is the Red Planet, and its colorful name refers to the high concentration of iron oxide (aka rust) in the planet’s top layer of rock and dust.

About an hour after sunset, face east and look for a bright luminary coming up over the eastern horizon. It’s not quite as bright as Mars, but brighter than Regulus, the star at the bottom of the Sickle asterism (star pattern). The Sickle marks the head of the constellation Leo the Lion. The bright newcomer is the ringed planet Saturn, and it has a golden-yellow hue. This coloration is caused by sunlight (from our yellow Sun) reflecting off the ammonia clouds in Saturn’s upper atmosphere.

By the way, massive Jupiter and petite Mercury, the other two naked-eye planets, are aligned too close to the Sun right now— from our vantage point on Earth— to be visible. But yes, they too display unique hues.

That’s my story, and I’m sticking to it.