Humankind has launched numerous space exploration missions since 1969, taking our technology, if not our bodies, to the edge of our solar system. Add to that the prolific output of the Hubble, the Chandra, and the Spitzer space telescopes: spectacular, surreal images of deep-space objects in the Milky Way, along with those beyond our home galaxy, billions of light years away.
Sometimes it feels as if I’m comfortably seated on the observing deck of a swift spacecraft, while brilliant scientists and engineers sweat it out in the boiler room in order to incrementally extend my view out the picture window.
Of course, my little conceit stems from our common, virtual experience of space. We are for the most part a species of armchair travelers, exploring the universe from the comfort of terra firma. Just a few brave souls suit up to ride rockets to the International Space Station and back. Only six times have humans landed on the Moon. Only six times have any of us looked back at Earth while standing on another world.
In 40 years, yes, our vision has penetrated far into the universe. But our footprints have not.
The Sea of Tranquility provided the site for the historic Apollo 11 moon landing in July 1969. You can easily spot this large dark feature, a lava-filled crater, with the naked eye.
Give it a try when the Moon is waxing (growing).
Astronomy Essential: A galaxy is a large system of stars and planets, bound by gravity and rotating around a dense core.
The word galaxy (GA-leck-see) derives from the Greek word for milk. Galaxies are typically categorized by their shape and/or their orientation to Earth. Some of the shape-based categories are spiral (like our home galaxy, the Milky Way), elliptical, lenticular, and irregular. Common orientation categories are face-on and edge-on.
There are an estimated 200 billion galaxies in the universe.