Stellar Parallax and Distance Measurement

The lecture explains stellar parallax, a method to measure distances to nearby stars. It begins with a simple demonstration using a thumb to illustrate the parallax effect. The lecture then delves into the geometry and calculations involved in using parallax to determine star distances, introducing units like parsecs. Limitations of the method are discussed, followed by an example problem to reinforce understanding.

What is the parallax effect demonstrated with the thumb exercise?

• The background moves instead of the thumb.

• The thumb does not move at all.

• The thumb appears to move less when it is closer to the face.

• The thumb appears to move more when it is closer to the face.

How does stellar parallax help in measuring the distance to stars?

• By calculating the brightness of stars.

• By measuring the apparent movement of stars against distant backgrounds.

• By counting the number of stars in a constellation.

• By observing the color change of stars.

What is the total angular distance in the context of stellar parallax?

• The angle of sight in July only.

• The angle of sight in January only.

• The difference between the angles of sight in January and July.

• The sum of the angles of sight in January and July.

What is the parallax angle used for in calculations?

• To find the exact distance to a star from the Sun.

• To calculate the speed of a star.

• To determine the color of a star.

• To measure the brightness of a star.

What is an arc second?

• A unit of time.

• A unit of distance.

• A unit of angle measurement, smaller than a degree.

• A unit of mass.

How is a parsec defined in terms of parallax?

• The distance at which a star has a parallax angle of one degree.

• The distance at which a star has a parallax angle of one radian.

• The distance at which a star has a parallax angle of one arc second.

• The distance at which a star has a parallax angle of one arc minute.

What is the maximum distance that can be measured using the parallax method?

• 10,000 light-years

• 1,000 light-years

• 500 light-years

• 652 light-years

In the example problem, what is the parallax angle if the total angular distance is 0.72 arc seconds?

• 0.36 arc seconds

• 1.44 arc seconds

• 0.18 arc seconds

• 0.72 arc seconds

What is the distance to star A in parsecs if the parallax angle is 0.36 arc seconds?

• 0.72 parsecs

• 1.39 parsecs

• 3.26 parsecs

• 2.78 parsecs

How many light-years is star A from Earth if it is 2.78 parsecs away?

• 5.00 light-years

• 3.26 light-years

• 12.00 light-years

• 9.06 light-years