09/20/2011 03:22 pm ET Updated Nov 17, 2011

Up on the Roof, Part 2

Events of September 14, 2011

We headed up to the roof of the College of Arts and Sciences building at 8:30. It was still a little hazy, and that combined with the lights of the city meant we couldn't see very many stars with our naked eyes. But the waning gibbous moon was very bright, and Jupiter was visible over the Charles River. I'd brought my binoculars, but because everybody was walking around on the metal floor of the observatory area, it was hard to keep the view still when leaning on the railing. That made the telescopes even more of a treat, because they were mounted to concrete pillars.

We looked at the moon near the terminator, or the line separating the night and day sides -- in this case, the "raggedy" edge where shadows were beginning to hide the face of the moon after the previous night's full phase. The longer shadows helped make the craters and mountains stand out -- one crater right on the terminator line had a large peak right in its center.

I chatted with one of the other students in the club about human-made space probes orbiting the moon, like the Lunar Reconnaissance Orbiter or the GRAIL mission that had launched just a few days before (but wouldn't actually get to the moon for a few months). I wondered how good a telescope we would need to see a probe if it passed between us and the moon's surface while we were looking at the moon. He did the math in his head and said that the telescope's mirror would have to be impossibly large, as well as above the Earth's atmosphere. Oh well, you can't have everything.

After the moon, we looked at the double star Albireo -- always a treat because it shows very dramatically that stars have colors and aren't all just white. One of the stars looks orange or gold, while the other is tinged blue. Just like the blue and white parts of a fire are hotter than the red and yellow parts, this means that the blue star is actually hotter than the orange one.

Jupiter looked just as stunning through the telescope, an orange disk on which I could vaguely make out bands of white. I could see three star-like objects around it, three of the Galilean satellites -- the moons of Jupiter discovered by Galileo just over 400 years ago. Galileo could probably see more stars from Florence than we could from Boston, seeing as he lived before electric lighting and all, but I had a feeling his sense of relaxation in turning to the skies after a long day was probably quite similar to my own. Some things don't change, even in 400 years.