Classification of stars Flashcards
What is luminosity?
The amount of energy something radiates per second (w)
What is brightness/intensity?
The power per unit area
What is apparent magnitude for brightest and faintest stars?
magnitude 1 for brightest, 6 for faintest.
What scale does the apparent magnitude obey?
A logarithmic scale. A difference of 1 is a multiplication of 2.51 for brightness.
What is one astronomical unit?
1 AU. it is the mean distance from the sun and the Earth.
What is one parsec?
The distance from which 1AU subtends an angle of 1 arcsecond.
What is the definition of absolute magnitude?
The apparent magnitude a star would have if places 10 PC from the Earth. It is a measure of the star’s inherent brightness.
What is formula linking absolute and apparent magnitude?
m-M = 5log(d/10)
What is a black body?
An object that absorbs all EM radiation that falls onto it.
What is luminosity proportional to?
radius squared and temperature to the fourth power
What is Wienn’s displacement law?
As an object is heated further, it emits radiation of shorter wavelengths. A black-body emits a peak maximum intensity wavelength of EM radiation.
Why do hotter stars appear to blue?
They emit most of their radiation at shorter wavelengths as they are very hot.
Why do cooler stars appear red?
They emit most of their radiation at longer wavelengths as they are cooler.
What is the spectral class memory tip?
Oh be a fine girl kiss me. Blue, blue, blue-white, white, yellow-white,orange,red
