A Celestial Soiree
In late May 2012 the Explorers gathered for an evening of stargazing and viewing through a telescope. Several celestial objects were putting on a show, including the moon and the planets Venus and Saturn.
The group began with a demonstration of the telescope. Like all telescopes, this one works by gathering more light (by means of an 8-inch wide mirror) than a human eye can normally hold. The telescope both magnifies (makes larger) and brightens objects seen in its eyepiece. Mr. Ramsey showed the students how the light enters the front of the telescope, is bounced and curved by the large mirror in back, is bounced back again by yet another mirror, and is finally focused at the back by an eyepiece. He also showed how the computerized system can find and track sky objects, compensating for their apparent movement across the sky as the Earth itself turns.
As the sun went down, the telescope turned toward the waxing crescent moon low in the western sky. Through the eyepiece, the students could see the craters of the lunar surface illuminated by the low-angle rays of the sun. The visible part of the moon was experiencing “morning,” meaning that each crater rim and mountain peak threw long sharp shadows across the surface, giving a strong three-dimensional impression to the view.
Later in the evening as the sky darkened the students could also view the phenomenon known as “earthshine.” This is the faintly visible glow of the dark portion of the moon, traditionally known as “the old moon in the new moon’s arms.” Earthshine is indeed literally light shining from the Earth—just as the moon lights up our nighttime landscape, the Earth lights up the moon’s landscape. As Mr. Ramsey explained to the Explorers, an astronaut standing on the “dark” portion of the moon facing the Earth on this evening would see a nearly full Earth, much larger and brighter than a full moon appears to us, shining down from high above.
Next the group turned its attention to the planet Venus. Venus travels around the sun in an orbit that is closer to the sun than our own path, and it therefore passes occasionally between us and the sun as it “laps” us on the inside lane. On this evening Venus was only a couple of weeks away from doing just that, and so it was growing ever closer (and larger through the telescope to us). Through the eyepiece it was a beautiful brilliant crescent shape, similar to the moon (and for the same reason—in both cases they were between us and the sun, with most of the lit side facing away from us). For the next week or so skywatchers could follow Venus on an apparent dive right toward the sun’s heart, until it came too close to be seen in the sun’s brilliance.
Actually, this was an extra-special passage toward the sun, as Venus would not pass near the sun’s disk but actually across it from our point of view. This event, known as a transit of Venus, is one of the rarest sights in the sky. Venus transits occur in pairs that happen eight years apart, with over a hundred years separating one pair of transits from the next. Before this transit in June 2012 came one in 2004, but the next pair of Venus transits will not occur until 2117 and 2125.
Finally, the telescope slewed to another part of the sky in search of what most in the group agreed was the evening’s true highlight, the planet Saturn. Saturn is in reality much, much larger than either the moon or Venus (or Earth, for that matter), but it is also much, much farther away from us than either of those other bodies. In the eyepiece, therefore, Saturn appeared somewhat smaller than Venus, looking like a cream-colored ball with several faint bands or stripes crossing it. Also visible were several of Saturn’s own moons, appearing as fainter dots of light near it. What makes Saturn truly fascinating, though, is of course its ring system, and despite the approach of some thin high level clouds in our sky everyone got a good look at the delicate rings surrounding the planet. Many of the students (and parents!) remarked that Saturn and its rings were an incredible sight, floating in the blackness of space.
To see some photos of our group during our stargazing session, check out the gallery. A few of the pictures are Mr. Ramsey’s—thanks to Mrs. Armstrong for passing along the rest!