Tom Burns: Galaxies, inside and out


Tom Burns - Stargazing



The best way to get a sense of humanity’s place in the universe is simply to go outside and look at the sky in early autumn. Of course, the universe is somewhat obscured by the glow of city lights. Why not take a late afternoon drive out to the country to watch the leaves change and stay there until the universe appears in all its glory? Don’t forget to take along binoculars or a small telescope for an even better view.

As twilight turns to darkness, look up with the binoculars you were born with, your own two eyes. The sky above glows with a strange, convoluted band of silvery light stretching from the southwest to the top of the sky and then to the northeast. You are looking at the distant stars of your own Milky Way galaxy, our cosmic neighborhood. The sun is only one of the Milky Way’s 300 billion stars, many of which are contained in the milky band you see. A simple set of binoculars is all it takes to make that band explode into countless stars.

The Milky Way is shaped much like an Olympic discus, wider at the center and taped at its edges. This cosmic discus is 100,000 light years from side to side. (One light year is equal to about 6 trillion miles.) Turn on a flashlight at one end, and the light takes 100,000 years to get to the other side. Turn on a flashlight and aim it at the moon, and the light takes a hair more than a second to travel the distance there. Compare one second to 100,000 years and you’ll begin to get a sense of the enormous size of the Milky Way.

We live near the edge of the Milky Way. As we stare into it, our vision of the larger universe is obscured by the glow of countless stars and clouds of dust and gas out of which stars are born. To get a sense of the texture of the rest of the universe, we must look away from the densest part of the Milky Way.

Thus, around 9 p.m., look to the east about halfway to the top of the sky for the constellation Andromeda, where only a thin veil of Milky Way gets in the way. Far beyond the stars of the constellation, you will see a fuzzy, cigar-shaped patch of light called the Andromeda Galaxy. With the unaided eye, the galaxy doesn’t look like much, but it will nearly fill the field of most binoculars. From our vantage in the Milky Way, Andromeda is tilted partly on its side, which accounts for its oval shape.

At perhaps 200,000 light years wide, the galaxy is twice the diameter of our Milky Way. Recent estimates by astronomers put Andromeda at around 2.5 million light years away. The light that you see took 2.5 million years to travel to your eyes. Into the enormous gulf between the two could be placed — end to end — more than 12 Andromeda galaxies and 25 Milky Ways.

And here is the simple fact will leave your mind gasping for oxygen: Andromeda is the closest large galaxy to our Milky Way.

The universe is composed of perhaps a trillion galaxies like Andromeda. If you spend a lifetime, a hundred lifetimes, staring through telescopes at every galaxy you can see, you will see but a tiny fraction of the galaxies that compose the universe, and every one of them will be far more distant than that faint smudge of light called the Andromeda Galaxy.

Stare upward at these things just once in your life. Stare long enough and you will know humanity’s place in the universe. Compared even to the smallest star, you are a tiny, fragile creation. Your body is small, but your mind measures out the universe as quick as thought. Perhaps you will come to know that you were given eyes to see these things. You were given a mind to share in the vastness of the universe.

Dance of the Planets

It’s worth getting up at 6 a.m. to check out the planets in the eastern sky during deep morning twilight. Venus is extremely bright and white. Down and to the left is Jupiter. Old Jove is a bit dimmer and has a slightly yellowish cast. Faint Mars is orange yellow and just above Jupiter.

Watch the planets dance! On Oct. 17 and 18, Jupiter and Mars will be side by side and less than a moon’s width apart. On Oct. 25, Jupiter and Venus will be next to each other with Mars below them. Venus continues to drop, so that by Nov. 2, Venus and Mars will be side by side with Jupiter above them.

Note that you’ll need an eastern horizon free of trees and tall buildings to enjoy the view.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.