magnitude

parallax

the apparent change of position of a nearer start in comparison to distant stars as a result of the orbit of the earth around the sun

parsec

a distance between the sun and the star when the parallax is 1 arc second. 1pc = 1Au/(1/3600)

apparent magnitude, m

a measure of how bright the object appears

hipparchus scale

a scale from 1 to 6. i si the brightest star in the night sky, 6 is the dimmest star we can see with the naked eye

ratio of intensities for two stars

I2/I1 = 2.51^m1-m2

absolute magnitude

the apparent magnitude of the object if it was 10 parsecs away

standard candle

an object whose absolute magnitude is known and whose apparent magnitude can be measured

peak absolute magnitude of type 1a supernovae

-19.3