Sky Watch: Finding the 7th planet

How many planets does our solar system have? Eight? Twelve? Two hundred? With the actual definition of the word "planet" still rather unsettled, you're likely to get as many answers to that question as there are astronomers to ask.

It wasn't always that way, however. Back in the good ol' days -- some two and a half centuries ago, for example, when life was much simpler -- every astronomer and schoolchild knew the answer. There were six planets: Mercury, Venus, Earth, Mars, Jupiter and Saturn, five of which wandered the starry heaven from night to night. And that's all that was ever known since the dawn of time.

That's why, in 1781, the world was stunned when musical composer and amateur astronomer William Herschel announced his discovery of a seventh planet. It was named Uranus in honor of Ouranos, the father of the Titans and grandfather of Jupiter in Greek mythology. Incidentally Uranus was then (and still is) pronounced YOU-rah-nus.

What's most curious is that Uranus wasn't found earlier for, you see, the planet can sometimes be spotted with the naked eye. In fact, right now is one of those times and, if you've never seen this planet, this is a great time to begin your search.

Uranus officially reaches its opposition -- the point in its orbit where it lies closest to Earth -- on Thursday, Oct. 3, and for the next week or so will rise in the east not long after sunset.

Finding Uranus takes some patience, but it's not too tough. After dark -- at a location far from city lights -- look midway up in the eastern sky for the Great Square of Pegasus. The top and bottom stars of the square point downward toward a faint star in Pisces known as Delta Piscium. If you aim binoculars in its direction, you may be able to spot Uranus on the right side of your field of view as a dim point of light whose unique bluish-green hue and steady glow distinguish it from neighboring stars. Through a small telescope, the planet appears as a distinct, though tiny, blue-green disk.

Once you know exactly which dot of light is Uranus and can identify the stars around it, try searching for it with your eyes alone. If you have good vision and a clear, dark rural sky far from city light pollution, you may be surprised by how easy it is.

Now if Uranus is this simple to spot with the unaided eye, why hadn't the ancients done so? And if they had, how might that have changed history?

After all, the five visible planets (plus the sun and moon) lent importance to the number seven, and we see it everywhere: seven rungs of perfection, seven emblems of the Buddha, the seven gates of Thebes, even the seven days of the week.

So it's only natural to wonder how things might be different had there been eight -- instead of seven -- significant bodies that traveled the heavens? Might we now have eight days a week?

Hmmm . . . you don't suppose that's what inspired John Lennon and Paul McCartney to write that famous 1964 Beatles hit song?

Naaahh.