You wanted to know
A student in Katherine Crawford’s fifth-grade class at West Oak Middle School in Mundelein asked, “How are other galaxies discovered?”
By Hope Babowice
Ancient people knew the sky was a vast expanse that contained many thousands of stars.
Anyone with a telescope today can look into the dark night sky and see hundreds of thousands of stars, many planets and even other galaxies besides our own solar system, the Milky Way.
The brightness of the stars may make them appear close, but they actually stretch out in an almost unimaginable distance from the Earth.
“Most of these stars are relatively nearby, only a few tens of hundreds light years away, which translates to hundreds or thousands of trillions of miles away,” explains Geza Gyuk, director of astronomy at Chicago’s Adler Planetarium.
What does the Milky Way look like? Dr. Gyuk said, “It consists of hundreds of billions of stars of all kinds spread out in a spiral disk that measures about 100,000 light years across. It took many years, even centuries, for scientists to gradually understand how the stars and planets were organized and the sheer size of the Milky Way.”
Other galaxies are similar in shape and size, and yet others are defined as elliptical and irregular shape.
The first time someone realized there was more than one galaxy was in the 1920s when cosmologist Edwin Hubble used a 100-inch telescope to identify and define two galaxies beyond the Milky Way — Andromeda and Triangulum.
Scientists have developed more high-powered telescopes, like the space-traveling Hubble telescope, to see there are many billions of galaxies — maybe 200 billion.
A percentage have been photographed and cataloged by scientists. NASA has a database with 4 million names, but scientists are sure that’s not all of them.
The discovery of galaxies beyond the Milky Way has led to many more revelations about our universe.
Once astronomers could see the galaxies that surround the Milky Way, they formulated the theory that the universe is expanding, they identified the existence of black holes in the centers of those galaxies, and they discovered places where new stars and galaxies are forming.
Gyuk said scientists use a special cataloging system to assign names or numbers to the galaxies.
“We can tell the difference between a galaxy, a foreground star, or cloud of gas and dust by looking at its shape and color. Stars are tight, compact points of light. Galaxies and clouds are more spread out and fuzzy.
“But a galaxy has a different color than a cloud of gas, so we can tell them apart. So there are still discoveries to be made about galaxies,” he said.
Readers are encouraged to help scientists classify the millions of galaxies by logging onto GalaxyZoo at www.galaxyzoo.org.
“You don’t need any training or experience and, who knows, you might discover something new and marvelous,” Gyuk said.
People of all ages are invited to look far into the distance of the night sky at the Lake County Astronomical Society monthly meetings. Free, the meetings include opportunities to see stars, planets and maybe even galaxies using telescopes. No registration is required.
Locations are at Volo Bog and local libraries throughout Lake County. Visit lcas-astronomy.org for dates and times.Copyright © 2014 Paddock Publications, Inc. All rights reserved.