Astronomy Questions

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Astronomy 1760-60

Fall 2010

Homework 2 Answers

Short Answer/General Questions: These should have short answers of a few sentences. 1. Explain the difference between speed and velocity and why this is important in acceleration. Give an example where an object is accelerating, but their speed is constant. Speed: Change in position over time – distance over time Velocity: Change in position and direction over time – distance and direction over time Acceleration: Change in Velocity, so a change in speed, direction or both. Example: A change in direction but not speed would be acceleration around a curve, where speed is constant but the direction changes, which means the velocity changes, which means that acceleration occurs.

2. Why is light so important in astronomy? We spent a large part of our lecture talking about light and the types of light – why does this matter so much in astronomy? What is the main way astronomers get information about things outside our galaxy? Light is important in astronomy because, outside the solar system, it is the ONLY thing that reaches us from any other place in the universe. All the information we have is from light. Light (viewed by telescopes and satellites) is the main way that astronomers gain information about the universe outside our solar system. Light tells us about the source object, the path it has taken, the things it has passed and anything it has gone through. Sometimes it’s hard to tell some of these things apart, but they are all in the light information we receive.

3. In class we talked about the three main types of energy – kinetic, potential and radiation. For each type of energy, give an example and explain why this type of energy fits in that category. Kinetic (energy of motion) – running, throwing a ball, swatting a fly, and so many things Potential (saved energy) – energy stored in a battery, energy stored in your body (from food) Radiative energy (light energy) – light energy from the sun (feels warm when you are outside, right?)

4. What is the difference between angular resolution and magnification? Give an example from everyday life about angular resolution vs. magnification.

Astronomy 1760-60

Fall 2010

Homework 2 Answers

Angular resolution vs. Magnification – Magnification means that you are enlarging an image that you already have, but you are not adding any more detail to it. You can increase the size, but you aren’t going to see any more. Angular resolution is the smallest angle between two points that allows them to still be distinguishable, and if you increase that, you add more detail to an image. Remember, that when you blow things up on the computer (magnify) the computer screen is limiting your angular resolution, so images may seem more detailed but that’s because the screen couldn’t show you the detail that was in the image. Once the angular resolution of the screen matches the image, you can enlarge it (magnify) it all you want, you won’t see more detail. But getting a higher resolution version of the same image and magnifying it by the same amount will allow you to see more detail because that picture has more information. Which is also why those files take up so much more room on your computer.

Think about it/Experiment Questions: These questions require a little more work and slightly more time, though none of them should take too long. 1. You find a planet orbiting a star that is roughly the same mass as our sun. This planet orbits in 63 days. Using either Kepler’s 3rd Law or the Newtonian version of it (it’s up to you, just make sure to show which you used) calculate the planet’s orbital distance and compare to the Earth’s orbital distance. Remember, these two ways will have answers in different units, so make sure you know what units you are working in to compare to the Earth. Make sure to show your work for the calculations which ever way you use. Below are a few helpful pieces of information: Kepler’s 3rd Law: pg....
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