This summer, you have an opportunity to make the same discoveries that Galileo started making in 1609. In June of that year, he built a telescope from descriptions he heard of its recent invention, attributed to the Dutch optician Hans Lippershey. Galileo built telescopes comparable to a modern pair of binoculars or that small telescope you bought for the kids and then relegated to the garage, beside the baseball gear. Go get it back out!
Galileo first observed the moon and discovered it was obviously not smooth, but rough and cratered. You can easily see craters, not visible to the unaided eye, with binoculars or a small scope. The imperfect moon was the first discovery to contradict the church’s view of a perfect, Earth-centered cosmos.
Saturn is up all night, and you can see the rings with a small scope, visible as the sort of “handles” that Galileo drew. Venus is still fairly high in the western sky at twilight. You should be able to see that it shows a shape like a first-quarter moon, and it gets more crescent-shaped throughout the month. Galileo realized that these moon-like phases cannot be produced with an Earth-centered cosmos.
Jupiter is close to Venus in the western evening sky. The binoculars or small scope will reveal its four brightest moons. Galileo’s observations revealed their changing positions from night to night. You can see that, too, and sense his discovery of the first observed orbital motion certainly not centered on our planet.
In the late evening, the Milky Way is above the horizon, and, by midnight, you can use your telescope to reveal it as actually a band of individual stars, too close and faint to resolve with the naked eye. Less than a century ago, we sorted out the difference between our Milky Way galaxy and the other galaxies, seen as fuzzy, spiral patches of light.
So now you’ve scored with the moon, planets and the Milky Way. To complete the celestial equivalent of baseball’s “hitting for the cycle,” you would need to add a fourth type of discovery observation, perhaps Galileo’s observations of sunspots. I have to advise you get the help of a professional or capable amateur astronomer to see sunspots. Never look at the sun, with or without optical aid. Maybe get that bullpen help from your local astronomy club.
Galileo’s discoveries spanned a couple of years, but you can easily complete your celestial grand slam in one night this summer. June 20 is a particularly good evening, given that Jupiter, the crescent moon and crescent Venus will all be grouped together after sunset.
Drag out that scope and invite the neighbors over to barbecue. Maybe surf and … AstroTurf?
Daniel B. Caton is a physics and astronomy professor and director of observatories at Appalachian State. Email: firstname.lastname@example.org. More on this column is at: www.upintheair.info.