When many stargazers first look at galaxies in telescopes, they are bitterly disappointed. “Is this what I paid $500 for?” they ask. “A smudge, a gol-danged fuzz ball?”
The view of galaxies that we get in our small telescopes would be the envy of professional astronomers just 200 years ago. A telescope with an eight-inch-diameter mirror gives views of galaxies that surpass what could be seen by high-powered ‘scopes just a short time ago.
As telescopes got bigger at the beginning of the 20th century, a bit of visual detail began to emerge from the fuzz. Many of these “nebulae,” as they were called, seemed to have a distinctly spiral shape, like a child’s pinwheel.
Many astronomers assumed that these “spiral nebulae” were part of our Milky Way galaxy. Because they seemed to be made of hydrogen, and hydrogen is the main constituent of stars, perhaps the spiral were clouds of gas slowly spiraling inward to form stars. The inner core of the spiral would, according to this theory, create a star. The spiral arms would swirl around the create planets like Jupiter and Earth.
As the century progressed, a new view began to emerge. Perhaps the spirals were made of stars. Perhaps they were Milky Ways, separate galaxies at great distances from our own Milky Way. Perhaps the universe was itself composed of “island universes.”
On the surface, the idea seemed idiotic. The Milky Way alone was thought to be tens of thousands of light years wide. (One light year calculates out to about six trillion miles). Even the Milky Way was big enough to make your brain melt if you thought too much about it.
Percival Lowell, who was wrong in many of his ideas, was one of the proponents of the solar-system supposition. To prove it, he asked one of his assistants, Vesto Slipher to study the spirals and record the spectra of the mysterious objects. Slipher was to break up their light into its component rainbow bands, which astronomers call its spectrum. If the bands resembled those of the planets of our own solar system, then the solar-nebula hypothesis would be proven.
Slipher began the tedious work in 1912. By 1915, he had taken the spectra of 15 galaxies, and the results were startling, to say the least.
Among other things, a spectrum tells an astronomer how fast an object is moving away from or toward Earth. Slipher dutifully calculated the velocities of his galaxies.
They were moving at unbelievable speeds.
The first galaxy that Slipher observed is in the constellation Corvus, the Crow. In a moderately sized amateur telescope, it does indeed look like the festive Mexican hat seen from the side. Look for a thin sliver of light topped with a hat-like central bulge.
The Sombrero galaxy appeared to Slipher to be moving away from us at the ungodly speed of 2.5 million miles per hour, the highest speed of any object known at the time.
Its recessional velocity simply could not be if the nebulae were mere gas clouds in our Milky Way galaxy. They must be far away, and if they were so far, they must be huge enough for us to see them at all.
Under the hot glare of Slipher’s observations and the further work of astronomers over the next 15 years, the solar-nebula hypothesis melted quickly away.
We know now that galaxies are island universes, vast disk- or egg-shaped collections of hundreds of billions of stars. They are separated from each other by brain-melting distances, leaving us with a universe so large that we are small indeed by comparison.
In fact, the rapid recession of galaxies appears to be the norm. That fact suggests that earlier in the universe, they had been closer together. Even earlier, they had been closer still.
Run the clock back to the beginning of the universe, and you end up with an unimaginably dense point in space that must have erupted with incredible violence to create the universe we see today.
Vesto Slipher could hardly have known in 1912 that his painstaking observation of the Sombrero would be the germ of the Big Bang model of the universe’s creation, a model astronomers believe to this very day.
If you have a telescope, go out some spring night and find the Sombrero Galaxy. Ponder, if you will, how small we are. Curse, if you wish, the tiny smudge you see. Personally, I prefer to think of Vesto Slipher and how one human can capture in the tiny colored bands of a galactic rainbow the vastness and majesty of the universe.
Don’t forget about the eclipse of the moon tonight. At 1:58 a.m., Luna will enter Earth’s shadow and slowly begin to disappear. By 3:08 a.m. the moon will be entirely ensconced by the shadow, and Luna will shine a bloody or coppery red.
Tom Burns is the director of Perkins Observatory. He can be reached at firstname.lastname@example.org.