Astronomy 181 Homework Assignment #1

Astronomy 181 Homework Assignment #1

DUE Thursday, October 16th

Part I: Observations

Using a star chart (such as your textbook appendicies, Skychart III software or other source) identify the locations of the stars α-UMi (Polaris) and α-Cyg (Deneb).

On a clear evening, measure the angular separation of these stars. Record the date, time and angle of your observation on the answer sheet provided. The angular separation is easy enough to approximate using the finger-tip, knuckle and hand scales mentioned in the Week 2 Lecture. If you are ambitious, find a better way of measuring angles in the sky. All that is required is a cheap plastic protractor, some string, and other bits that you probably have around the house (and some common sense). Remember that measurement of the stars began in ancient times.

After sunset on any given day, locate α-Peg (Markab) in the eastern sky. It is the brightest star in the constellation Pegasus and is located not far from α-Cyg. Measure its angular position relative to due east on the horizon (you may want to use a compass for this if you are unsure of due east). Record the date, time and angle of your measurement. After an hour has passed make another measurement and record the new time and angle. Subtracting the two angles gives an interesting result. How it this explained?

Part II: Explanation

This picture is from the Week 2 Lecture. One of the chief driving forces in the development of Astronomy is the desire of inquisitive humans to explain curious observations in the sky. Most often, the answers are simple, and make obvious sense. That does not mean that they were easy to discover!

This picture is a collection of pictures taken of the sun at noon throughout the course of the year. We all understand that the sun is higher in the sky during the summer and lower in the sky during the winter due to the 23.5º degree tilt of the earth relative to the plane of its orbit.

It is curious, however, that the sun should appear to shift left and right during the year.

Can you explain this?

Astronomy 181 Homework Assignment #1

ANSWER SHEET

α-UMi (Polaris) and α-Cyg (Deneb)

Date:______Time:______Angular Separation:______

METHOD:

α-Peg (Markab)

Date:______Time:______Elevation Angle:______

Date:______Time:______Elevation Angle:______

Difference in elevation angle: ______

EXPLAINATION: