The Center of It All

9/4/05 – 9/10/05

By C. Zaitz

For many years, astronomers have been trying to glimpse the center of the Milky Way Galaxy. Regular optical telescopes won’t work- the dust and gas in the space blocks our view. We can only peer about a thousand light years into our galaxy before the view is obscured. The center is much farther, about 30 thousand light years beyond.

How then can we ever get a true picture of what lies at the center? We must use other types of telescopes that see in wavelengths beyond the limits of the human eye, wavelengths the size of an atom or less; x-rays and gamma rays. The earth’s air absorbs these waves, so in order to detect them we have to send telescopes above the air.

When we look for gamma rays and x-rays, we see the galactic center region aglow. X-rays are generated from the interaction of two stars orbiting each other, or should we say “former” stars. In these binary systems, one star has evolved into a black hole, and the other is being cannibalized by the black hole. As the black hole rips gas from the remaining star and swallows it, powerful x-rays are emitted and our telescopes can make an image.

Gamma rays, on the other hand, come from the annihilation of matter and antimatter. It does happen in nature, not just on Star Trek. While astronomers have not said exactly where the antimatter comes from, they use terms like, “violent and exotic environments” and “star birth, neutron star collisions, and black holes at the Galactic Center.” Neutron star collisions - now that sounds exciting! Both x-rays and gamma rays give us images of a very crowded, rather violent region of space.

So what does our picture of the galactic center look like? If we lived on a planet around a star in the middle of our galaxy, we would have a very different night sky. Our skies would be filled with hundreds of bright stars, some moving at speeds that we could actually detect. Imagine having constellation patterns change drastically over the course of your lifetime. There is a good chance that we might witness the greatest release of energy the modern Universe has; the explosion of a star. Though the sight might be glorious, we’d better be ready to flee to avoid the outward rush of killing radiation that follows the blast. With all the x-rays and gamma rays being created by the death throes of stars and the eating habits of black holes, life on our planet would be rather dangerous, if not impossible. Especially if we were to get too close the center of it all. Astronomers are pretty convinced that there is a gargantuan black hole lying there, crouched, waiting for passing stars and gas clouds to come just close enough to…slurp! There goes our star, our planet, and our plans to paint the house next spring.

Luckily we are safe and sound on our earth, far from the center. We can look toward the constellation Sagittarius, low in the southern sky, and know that we are looking in toward the middle of the Milky Way. While we are pondering our fortuitous position in the galaxy, we should spy on the planets. On September 6th, Jupiter and Venus will be visited by the passing crescent moon. Look to the west at Sunset. Venus is the brighter of the two planets, and the moon will look like a lazy smile.

Until next week, my friends, enjoy the view!