Brightness of Stars

Question 1

Why can we only see 2000-3000 stars in the sky?

Answer 1

-too far
-cosmic dust can obscure the view
-star is too small
-temp of the star

Question 2

Why are distances to planets in km, while the distances to stars and galaxies are in ly?

Answer 2

They are so far away

Question 3

What is the current estimate for the number of galaxies in the universe?

Answer 3

100 billion

Question 4

What is the estimated volume of our universe?

Answer 4

1x10^30 cubic lightyears

Question 5

What is a baseline?

Answer 5

-Baseline is an imaginary line from which the distance to an object is measured
-The diameter of Earth’s orbit is the longest baseline possible
-In astronomy, the distances are very large, and a larger baseline increases the accuracy

Question 6

Why does parallax only work for stars less than 200 ly away?

Answer 6

At distances further than 200 ly, the angles involved are too small, creating too many observational errors

Question 7

When using triangulation to determine distances indirectly what can you do to improve the accuracy of your measurements?

Answer 7

Use bigger baselines

Question 8

What is a Cepheid variable star and what makes it a variable?

Answer 8

Cepheid variable stars are unstable, yellow supergiants that pulse, or change in size and brightness

Question 9

Why is a Cepheid variable star referred to as a standard candle?

Answer 9

They pulsate over regular intervals (this correlates with how bright a star is)

Question 10

Observations of a pair of Cepheids reveal that Cepheid A is pulsing faster than Cepheid B. Which of the 2 has a greater absolute magnitude?

Answer 10

Cepheid B

Question 10

What is the difference between absolute and apparent magnitude?

Answer 10

Absolute magnitude is the actual amount of light a star gives off, while apparent magnitude is how bright a star appears in the night sky

Question 10

What is the connection between a Cepheid variable star’s pulse and its brightness?

Answer 10

the larger Cepheids pulse slower and are brighter

Question 10

What 2 conclusions can an astronomer make about a galaxy with a slight red shift and a galaxy with a large redshift?

Answer 10

The more red-shifted a galaxy is, the faster it moves, and the farther away it is

Question 10

How does the brightness of a light source change with distance?

Answer 10

At different distances from the observer, the different light sources appear as the same brightness