assignments
Planetary Challenge
Cold, clear skies in New England mean bundle up and head outside for some stargazing. The atmosphere is dry and, at least for tonight, the clouds are being held at bay by a high pressure system. See if you can catch the line up- this one is a challenge- in the sunset tonight. Look Southwest and find Jupiter. Then, with good timing and a clear horizon, you’ll be able to spot the very thin crescent Moon on a line down to the setting Sun. With sharp eyes, you can even catch the planet Mercury- if you do this, you should consider yourself better than a beginner! For those of you with telescopes, Jupiter is in conjunction with the telescopic planet Neptune tonight.
An new interpretation of the Cassini-Huygens mission
A whimsical look at the Cassini mission to Saturn, from one of my students.
A Moon Phase Simulator.
Click here for an excellent interactive moon phase simulator. Use the following questions to challenge yourself with the simulator:
1.) What time is it when the first-quarter moon sets? Answer is here.
2.) A thin sliver of the moon is visible just before sunrise. What phase is it? Answer is here.
3.) What is the angle between the moon and the Sun when the moon is 10 days past new? Answer is here.
Want more practice problems? Click here. Answers to be posted early next week. Careful, number 5 is pretty challenging!
Handouts
Planetary Disappearing Act
Tonight’s sky features Jupiter right next to the Moon.
If you train a telescope on Jupiter later on (around 12:30 a.m.), you’ll see the moon’s of Jupiter disappear (only to reappear two hours later). The next time this will happen is 2019.
Student work at Cahall Observatory
Recently, a senior here completed a project at the Cahall Observatory that spanned several weeks of independent observation and study. Here is his summary of his work.
Another senior project from 2007 is here. This is a Users Manual to Cahall Observatory’s system.
Assignment: Estimate the Speed of a Satellite
This is another picture that does not look like much. The telescope was tracking a GPS satellite. As the telescope moved to follow the satellite, the stars left trails on the CCD chip. I think this was a 30-second exposure.
There is enough information here to estimate the speed of the satellite. Well, almost enough. If you know the distance to the satellite (12,500 miles), you can use the technique described in the Comet Lulin assignment to figure out the speed of the satellite. The field-of-view is the same for the satellite and the comet images. Post your answers on the blog!
GPS satellites form a constantly moving ‘constellation’ of satellites that come in and out of view. If you pay attention to a GPS receiver, you might notice that it sometimes says ‘acquiring satellites’ or something like that. This animation will help you understand that.
NASA has a three-dimensional applet that allows you to track satellites in real time. This is a lot of fun- the directions are simple, and are in the window below the pop-up. The number of satellites is astonishing. If you want to know when the Space Station and other bright satellites will be over your neighborhood, go here.
Assignment: measure the speed of a comet.
This is Comet Lulin, photographed over the course of a half-hour on the night 0f February 24, 2009 (thanks to Jen and Anna). Each image is a 2 minute exposure; the telescope was tracking the background stars.
The field-of-view in this image is slightly less than a full moon. I estimate that the comet is moving about an eighth of a degree in this sequence. At a distance of 38 million miles, this movement across the frame represents about 80,000 miles. Since that took a half of an hour, the speed of the comet relative to Earth would be 160,000 miles per hour.
There are some incredible images of Comet Lulin here.
Cahall Observatory 