02 brightness

Question 1

The magnitude (brightness) of an object’s brightness can be referred to as either:

Answer 1

Absolute or Apparent.

Question 2

Apparent brightness is

Answer 2

how bright the star appears to a detector here on Earth. Apparent magnitude ranks stars by how bright they look from Earth.

Question 3

Absolute brightness is

Answer 3

a measure of how luminous a celestial object is. Absolute magnitude ranks stars by how bright they would look if they were all equal distances (33 ly) away from Earth.

Question 4

The magnitude scale seems a little backwards:

Answer 4

The lower the number, the brighter the object
The higher the number, the dimmer it is.
This scale is logarithmic and set so that every 5 steps up equals a 100 times decrease in brightness.
So magnitude 10 is 100 times dimmer than magnitude 5, which is 100 times dimmer than magnitude 0.

Question 5

Luminosity is

Answer 5

the energy emitted per second by the star. Magnitude of brightness from dim to very bright. Directly related to size.

Question 6

Main Sequence stars vary widely in effective temperature but

Answer 6

the hotter they are, the more luminous they are

Question 7

Stars are classified using 2 properties:

Answer 7

Luminosity and temperature

Question 8

Temperature

Answer 8

How hot the star is. Directly related to colour (blue is hottest, red is coolest).