Exploring the Sky 2 Flashcards
Lectures 4-8
If a star is fainter, it’s magnitude will be…
Higher
What is Betelguese’s magnitude?
0.45
What is Rigel’s magnitude?
0.18
What is Polaris’s magnitude?
1.97
If the magnitude difference is 1, what is the brightness?
2.5
If the magnitude difference is 2, what is the brightness?
6.3
If the magnitude difference is 3, what is the brightness?
16
If the magnitude difference is 4, what is the brightness?
40
If the magnitude difference is 5, what is the brightness?
100
What magnitude can the naked eye see?
6 magnitude and higher
The area of a lens is proportional to the square of what?
It’s diameter
Why do some stars have variable magnitude?
Because they pulsate
In some cases, the period of pulsation is related to what of a star? (2 factors)
Size and Luminosity
What have Cepheid vairables become important for?
Establishing the distance of external galaxies
How are Cepheid variables used to establish the distance of external galaxies?
Their apparent magnitude is measured the matched with the intrinsic brightness of Cepheid variables in the milky-way
Solar time is defined as what?
The hour angle of the sun plus 12 hours
What does the hour angle of the sun depend on? (2 factors)
- The rotation of the earth
- The sun’s revolution around the ecliptic
