jschaeffer

Imagine a clear night at the Van Vleck Observatory, you and all your friends have decided to come to a weekly Public Observing Night and take a look at the stars. You walk into the large dome atop Foss Hill and see the magnificent 20″ Alvan Clark Great Refractor before you. It seems to be pointed at a particularly bright star in the sky, and just as you’re about to put your eye to the eyepiece (the above picture shows you almost there), you realize that’s no star, but in fact the planet Jupiter.

You see large bands of clouds, part of the planet’s turbulent atmosphere. Nearby to Jupiter are four other points of light. This time they aren’t stars or planets but instead are Jupiter’s four largest moons. Known as the Galilean Moons or Galilean Satellites, they are named after Galileo Galilei who discovered them in 1610.

From left to right in the image the Galilean Moons are Callisto, Ganymede, Io, Europa. These moons are wonderful specimens in the menagerie of solar system bodies. Callisto is a crater-filled world; Ganymede a moon larger than Mercury; Io a volcanic world locked tight in Jupiter’s gravity; and Europa an ice-covered body with possible liquid oceans underneath. If you’re timing is just right you may even be able to see one or several moons pass in front of Jupiter; from the Jovian cloud tops you’d be privileged enough to see something akin a solar eclipse.

In addition to being an impressive view, Jupiter and its moons have also played an important role in the history of planetary impacts and determining the speed of light.

Speaking of history, the 20″ refractor telescope saw it’s “first light” on 26 July 1922. In the intervening years, up until the 1990s, it was used for research determining the distance to close stars. Distances were determined by a method known as parallax, where you look at the movement of a nearby star compared to much farther ones. A simple example of parallax is looking at your finger through one eye, then the other and seeing its position change compared with objects in the background.

Currently the telescope is used for public observing, as the photographic plates it used for imaging and measurements have mostly gone the way of the dinosaurs (or Pluto’s planet status for that matter). The rosy glow you see around the eyepiece is from lights in the dome tinted red to help preserve your night vision.

Now slaked of your thirst for the celestial, you and your friends leave with a bounce in your step, knowledge in your head and a feeling that you’re king of the world after having seen this most regal of planets.

(N.B.: This image, taken on 1 Dec 2011 ~2109EST, is an overlay of many different exposures, as my camera is not nearly as good as the human eye at adapting to different light levels.)

A note: Just as the plans of mice are wont to do, so too have my own to post an astronomy picture every week gone awry. I therefore am changing this to Astronomy Pictures of Whenever, allowing more freedom in when they can be posted as well as retaining the fetching acronym APOW.

We have here a view of the Van Vleck Observatory library at night. Taken around the end of August 2011 there are many things astronomical to see. How many can you find?

Starting on the left we can see a celestial globe displaying the positions of stars and constellations for the year 1800. You can get a better feel for what this is showing by imagining that the Earth is inside the center of this globe and you are looking outward at these constellations. You can see in the upper right portion the constellation Boötes, the herdsman (by his right arm is the label for this celestial globe: “Cary’s New and Improved Celestial Globe”). To his right is Serpens Caput, the head of the snake with which Ophiuchus (unseen) wrestles. In the bottom portion can be seen the tail of Hydra, the sea serpent which Hercules was tasked to kill.

In the distance just to the right of the celestial globe can be seen part of a 150ft wide, 60-million pound meteor which slammed into Earth approximately 50,000 years ago forming the 1-mile wide Barringer “Meteor” Crater in Arizona . This roughly one cubic-foot, nickel-iron meteorite chunk weighs an impressive 370lbs!

Splayed on the floor in front of the meteorite we have moonlight streaming in through the window. Hearkening back to the previous APOW (‘Star trails’), if you were to watch this moonlight for even a few minutes you would notice its movement across the floor caused by Earth’s gentle rotation.

Reflected in the far right window can be seen 20th century photographic plates of celestial objects taken at various different observatories, including our own. In the window pane furthest to the right can be seen an image of the Andromeda galaxy (née ‘Andromeda Nebula’). The light we see from the Andromeda galaxy left around the time when primitive humans were first fashioning stone tools and our current species was no where close to existing. Over the intervening few (~2) million years our current species evolved, we domesticated plants and animals, invented writing and spread across most of the world. During all this time the light from Andromeda was still hurtling towards us through space. The Ancient Egyptians, Greeks and Romans came and went; the Pyramids, Parthenon and Colosseum were built. The light was still chugging along. Bill Shakespeare wrote sonnets and some plays; Galileo pointed a telescope at the night sky, then got in trouble; Newton took a sick day and invented calculus, discovered fundamental laws of motion. The light, still cruising along at 67 million mph, was now within the bounds of our Galaxy. The United States was founded, split and reformed. The light, well outside our solar system, was still further than even the nearest stars. Then one clear night, likely in the second half of the 20th century, an observer at the Yerkes Observatory in Wisconsin decided to turn their 24-inch reflecting telescope (the same size and model as our very own) towards the Andromeda galaxy for 4.5 hours. The light (photons), after their many millions of light-years journey from Andromeda, ended by being absorbed in the atoms and molecules of a curious astronomer’s photographic plate. The light having traveled so long that a species was able to evolve, invent tools, and create a state decidedly the shape of Wisconsin, such that an observer could ‘trap’ these photons on a plate of chemicals at the end of a tube of mirrors, instead of having their journey be all for naught by bouncing off the observatory’s roof.

To the left of the reflected photos we see the portrait of our observatory’s namesake: John Monroe Van Vleck, head of Wesleyan’s Department of Mathematics and Astronomy in the mid-1800s. Underneath him are photographic plates (unlit) showing the bountiful starfields visible in our own Milky Way Galaxy, you’ll have to come see them for yourself; below the plates are more than 50 years worth of astronomical research journals.

So with that, and under the watchful gaze of J.M. Van Vleck, we end our astronomical tour of this delightful little library. Adieu.

Here is the first in a series of APOWs (Astronomy Pictures of the Week) which I’ll be posting most every Friday. These will be pictures taken of Van Vleck Observatory (VVO) itself or those from our telescopes out into the cosmos. Now without further ado…

The Earth’s rotation can be a blessing allowing us a cycle of light and dark along with an ever changing view of the sky. This same rotation can also be found a burden, requiring precise telescope tracking mechanisms to observe a celestial object for any extended period of time; similar, though undoubtedly cruder, mechanisms being required of umberphilic beachgoers.

Through a non-tracking telescope one can see the Earth’s rotation in real time, objects slowly drifting across the eyepiece’s field of view; by naked eye the rotating sky can only be detected as discrete changes over the course of an hour or so, the motion itself too slow to be seen by the casual observer. (If you look very closely at shadows cast by moon- or sun-light, or the image they make of windows on the floor, for example, you can better see this motion occurring).

Below is a video showing the ‘circumpolar motion’ of stars about the North Celestial Pole, which is quite close to Polaris; it was taken with my personal camera from the 16″-telescope’s dome, on the roof of VVO. The 30sec video consists of approximately an hour’s worth of photos strung together:

Circumpolar Motion_approx1hr

Along with watching these photos sequentially, they can also be overlaid to create ‘star trails’. Below is an overlay of the same photos used to make the movie above. The gaps in the trails are due to a few minutes between the end of one round of photos and me starting the next, planes can be seen streaked along the bottom, and a dark band below Polaris running up and to the right is likely due to exposure issues for a specific round of photos.