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Uranus

Summary: Uranus is one of the distant worlds of the solar system.  It orbits the sun about 19 times further away from the Sun than the Earth and takes 84 years to complete one orbit. Uranus is so far from us that the light we receive from it took over two and a half hours to reach us! When you look at Uranus through the telescope, you see it at where it was and how it looked 2.5 hours ago. Together with the even more distant Neptune, it forms the family of planets known as "ice giants". Like Jupiter and Saturn, "ice giants" are mainly gaseous planets, but they are mostly made of material that can form ices at very low temperatures, such as water (H₂O), methane (CH₄), and ammonia (NH₃) rather than the hydrogen and helium found in Jupiter and Saturn. The presence of abundant methane in their atmosphere gives them a distinctive color. Uranus is about 4 times larger than the Earth.

Goal: As you will soon realize, Uranus is really far away (about 1.7 billion miles!) and looks very small. In this lab, you will use your skills with the telescope to star hop to Uranus and make a basic observation of this cold, distant planet.

Due Date: October 31.

Procedure

1. 1. Getting Started: As always, note the date, time and atmospheric conditions. Is the sky clear, partly cloudy, high cirrus clouds? Is the air moist? Is it windy? How does this night compare with other nights on which you have observed (better? worse? in which way?).

2. Locate Uranus: Using the 25 mm eyepiece, find Uranus in the telescope using the chart provided by your TA. Note that Uranus is not visible to the naked eye from campus but it appears as a faint star in the finderscope. You can use the method described in the Star Hopping lab to find the planet. Switching to the 10mm eyepiece will allow you to confirm your find. At this magnification, Uranus should look distinctively different from a star. You should be able to see the tiny disk of the planet while stars remain close to pinpoints.

   You can get a finding chart for Uranus for the Fall of 2003 here. You will want to download and print out this finding chart. You can start your star-hop by locating either Delta Capricorni or Beta Aquarii, both of which are labelled on your SC-001 star chart.

3. Sketch the field of view around Uranus: Sketch the position of Uranus among the stars as seen through the finderscope. Use the generic template to make your sketch. Identify Uranus on you sketch and surrounding bright stars (if any). Indicate the orientation of your sketch (direction of North and East in the field of view). You can determine these directions by moving the telescope around one axis at a time. If you move the telescope in declination toward the South (lower declinations), objects will drift North in the field of view. Similarly, if you move the telescope in Right Ascension (using the slow motion knob) towards the West, objects in the field of view will appear to drift East. Finally, indicate the scale of your sketch. Use the field of view of the finderscope (determined in the Field of View lab) as your "measuring stick."

4. Take some notes: Switch to the 10 mm eyepiece and take some notes about the appearance of Uranus. There is no need to sketch but provide a detailed description. Comment on size, color, etc.