Urban light pollution has robbed many of us of one of nature's grandest spectacles: the hazy glow of the Milky Way. But the opening days of autumn are the perfect time to find a dark sanctuary in the countryside and get reacquainted with our starry home. Nights are still warm, the air is getting drier, and the center of the galaxy, the brightest, thickest part, shimmers in the sky at the end of twilight.

Click here: Milky Way / Learn More

Ancient cultures widely regarded that band of heavenly light as a splash of spilt cream. The Romans called it Via Lactea, the "road made of milk." (Via Galaxias)

When Galileo turned his spyglass (telescope) to the skies in 1610, he was amazed to find that the Milky Way is in fact "a collection of innumerable stars distributed in clusters." You can dramatically confirm his discovery using a pair of cheap binoculars.

Click here: Whirlpool Galaxy A / Whirlpool Galaxy B

Modern telescopes have provided deeper insights into our galaxy. Clouds of gas and dust from the Milky Way overhead, block the light from the galaxy's inner regions. Optical telescopes can peer only a few thousand light-years through the haze.

Telescope

But just as tinted sunglasses cut through solar glare, recent infrared, radio, and especially X-ray telescopes can penetrate all 26,000 light-years to the center of the galaxy.

Spiral Galaxy

Arecibo Radio Telescope Observatory (shown below)

Dying, massive stars with hot gases illuminate a Chandra X-ray image of a supernova remmant in our galaxy (shown below).

Chandra X-ray Image: Supernova Remnant

Last year NASA's orbiting Chandra X-ray Observatory produced a splendid view of the galactic core and found evidence that it harbors a black hole as massive as 2.6 million suns! The giant black hole that resides within the bright clump in the middle of our galaxy is just one of many unexpected galactic features unveiled by sophisticated telescopes.

Supermassive Galactic Black Hole

This black hole beast is now strangely silent. Astronomers believe that black holes radiate X-rays powerfully only when they are scooping material into their gravitational belly. These days, the black hole at the heart of the Milky Way does not seem to have much to gobble. But as recently as the American Revolution, according to one theory, it feasted on enough infalling matter to energize the surrounding X-ray gases that swish like the tails of cats.

Infalling Matter

Detailed studies of infrared (heat) radiation and star motions in our galaxy have revealed a cigar-shaped gathering of stars, 15,000 light-years across.

Star tracking also reveals that our galaxy is surrounded by a gigantic, near-invisible shell of matter, like a ship in a bottle.

Extending outward at least 150,000 light-years, this halo consists of dark matter that accounts for most of the Milky Way's mass.

Galaxy showing Halo of Dark Matter

Last year researchers determined that at least part of the invisible stuff consists of white-dwarf stars, which are the dim, collapsed corpses of middle-weight stars similar to our sun.

Some parts of the Milky Way are hidden not in space but in time. Over a human lifetime, the structure of the galaxy barely changes, but every star in the sky, including the sun, with Earth in tow, whirls around the center once every 240 million years.

Even at a breakneck speed of 137 miles per second, we have completed fewer than 20 revolutions around the galaxy since our planet's birth.

Think of our galaxy as a merry-go-round as you gaze at the speckled view above your head. Most of the stars we see in the night sky are those within our own Milky Way Galaxy.

Merry-Go-Round

Our sun is located three quarters of the way out on the Orion Arm of the Milky Way Galaxy (shown below). The other named arms of our galaxy include: Cygnus, Perseus, Centaurus and Sagittarius.

Early man gazed at the sky with bewildered eyes. Today, using telescope technology, we have a greater understanding of our galaxy. What new discoveries will occur in the future?

Only time will tell...

Courtesy of Bob Berman
DISCOVER Vol. 23 No. 09 | September 2002