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For those of us in the northern U.S. or Canada or at a similar latitude, the Big Dipper is always above the horizon. That means it is described as circumpolar. The mnemonic to remember for the Big Dipper is “spring up and fall down” to describe its appearance in our northern sky.
The Big and Little Dippers are asterisms – a prominent pattern or group of stars, typically having a popular name but smaller than a constellation. The Big Dipper ascends in the northeast on spring evenings, and it descends in the northwest on fall evenings.
“Follow the Drinking Gourd” is an American folk song that used “Drinking Gourd” as another name for the Big Dipper. The lyrics, according to legend, came from a conductor of the Underground Railroad, called Peg Leg Joe, as a way to guide some fugitive slaves.
The “drinkin’ gou’d” alludes to the hollowed out gourd used by slaves (and other rural Americans) as a water dipper. Used in the song, it was a code name for the Big Dipper which points to Polaris, the Pole Star, and to the North and freedom.
Polaris is a special star because it always stays in the same spot in the northern sky. The entire northern sky appears to turn around it because Polaris is located more or less above the northern axis (pole) of the Earth, and the wheeling of the stars across the dome of night is really due to Earth’s turning, after all. Polaris is part of the harder to find star pattern known as the Little Dipper.
Remember back in 2006 when poor, old planet Pluto was demoted? A group of scientists decided that there are three main categories of objects in our solar system:
Planets: 8 from Mercury to Neptune.
Dwarf Planets: Pluto and any other round object that “has not cleared the neighborhood around its orbit, and is not a satellite.”
Small Solar System Bodies: All other objects orbiting the Sun.
This past week I read that the waxing gibbous moon outside my window was moving toward the star Aldebaran, the brightest star in the constellation Taurus the Bull. Nothing odd about that. Normal movement.
But what I had not known was that Aldebaran also had a kind of demotion. It used to be the North Star, also known as the Pole Star. How does a star lose its rather prominent name in the sky?
You probably learned that Polaris is the North Star, but a long time ago Aldebaran had that honor. That was 450,000 years ago.
Back then, it appeared several times brighter in the sky then than it does now. In a way, it shared the title because it was very close to another very bright star, Capella, so they served as a double pole star. (This was 447,891 BCE, if you like precision.)
That’s pretty amazing, but it was a long time ago. But what really hit me was that in this little solar system of ours and in our beautiful galaxy and this almost unimaginable universe, everything is always moving.
Even the sky looked different hundreds of thousands of years ago.
The identity of the pole star shifts over time, due to the 26,000-year cycle of precession. To read more about that, click into this article about Thuban, another former pole star.
Still, how can it be, you might wonder, that the stars Aldebaran and Capella were once so near each other on the sky’s dome? They’re not especially close together now. Aren’t the stars essentially fixed relative to one another? The answer is that, yes, on the scale of human lifespans, the stars are essentially fixed. But the stars are actually moving through space, in orbit around the center of the galaxy.
The Moon is moving across the constellation Taurus and, in the Zodiac, Aldebaran is important. It is part of that merry band of stars in front of which the Sun, Moon, planets, dwarf planets and small solar system bodies dance their rounds.
The Earth is spinning as I sit here typing. It is making the moon and Aldebaran shift westward but the Moon is moving to the east relative to the “fixed” stars because of the Moon’s orbit around us. It is all so amazing. Some people think that looking up into that giant sky makes them feel so small. I disagree. It makes me feel a part of something so enormous and grand.
Hello, Aldebaran. We didn’t forget you.