Take a summer stroll in the night-sky neighborhood
Thanks to the Hubble telescope, we know the universe contains more than 40 billion galaxies. And for the first time, the Cosmic Background Explorer satellite gives us a single picture of the entire Milky Way, our "little" home in space, and a spot well worth getting to know this summer.
In fact, with the warm weather, it's a great opportunity to stroll around the neighborhood.
If you're in the city or crowded suburbs, take your family and friends for a drive in the country to a place where the night sky does not compete with neon. Bring a blanket, bug spray, and a flashlight with a red light (white light keeps our eyes from adjusting to their innate night vision).
The best time for stargazing is after midnight, with no moonlight or clouds. Dates when the skies will be moonless this summer include: June 6-14; July 6-14; August 4-12.
After your eyes adjust to the dark, take in the quiet grandeur of sparkling infinity. Watch long, and steadily. Bring along a pair of binoculars. Engage with the Milky Way, travel within its infinite vastness, and your imagination will be changed forever. As you look out into space you are looking back in time, thousands and millions of years back.
We live in a medium-sized spiral galaxy that is a relatively flat disk shape with a bulge in its center and spiral arms that radiate from its center like a colossal cosmic pinwheel. It stretches 100,000 light-years from side to side, and 13,000 light-years from top to bottom at its center.
Spiral galaxies have an extended halo of faint, billions-of-years-old stars at their extremities. Their disks are rich in gas and dust, while the galactic bulge or nucleus at the center contains the greatest number of newly formed stars. If the Milky Way were a city, our sun would be in a distant suburb, 27,000 light-years from the galactic center.
One way to wrap your imagination around the size of our galaxy is to realize that it takes the sun 240 million earth years to make one orbit around the Milky Way. Given that our galaxy is some 4.5 billion years old (and our sun is traveling at 484,000 mph around the galaxy, give or take 25,000 mph), it has made 20 revolutions around the Milky Way.
In June, the mid-latitudes of the Northern Hemisphere tilt toward the sun more directly than at any other time of the year. Nights are shortest and warm. This season offers the most favorable conditions for observing (not just looking at) the luminous river of stars that comprise the Milky Way streaming from north to south across the sky.
Remember, you are looking into the Milky Way (and just a part of it; you can't see through to the other end). What you are seeing represents a narrow band of the sky, albeit where the most stars are visible to the naked eye.
I grew up in New York, three miles from Kennedy Airport. When someone said, "Look, there's the first star," my reaction was a shrug. There would only be a couple of dozen visible. But my attitude changed when I was 19 and lived in a rural valley in southwest Mexico.
My first night there, I looked up at the sky and asked, "What's that funny cloud?" It was the Milky Way, stretching as far as my eye could see and my neck could crane. At that instant, my whole being was tranformed. and what I saw became the felt presence of infinity.
Looking for planets, stars, and constellations links us to one of the oldest activities of the human race. It is our destiny to look up. This column will share that destiny. And first, we need to get a feel for the forest rather than the trees. The Milky Way is a star forest.