The measure of the brightness of light from a star or other object as measured from Earth.

The wavelength range of light over which an observation is made.

The magnitude of a star derived either from the total energy that it radiates at all wavelengths or from the total energy of those of its wavelengths that are received on earth.

qo

a positive value of the deceleration parameter means the universe is slowing down, a value of 0 means the universe is expanding at a constant speed, and a negative value means that the universe is accelerating.

W0

Which lack spiral arms, are composed almost entirely of population II stars. Elliptical galaxies are actually of ellipsoidal shape. Normally, elliptical galaxies contain very little or no interstellar matter, and consist of old population II stars only: They appear like luminous bulges of spiral galaxies, without a disk component. These galaxies ar [..]

The material between the stars which is composed of gas and dust.

Total amount of energy radiated per second. It has units of energy per second (e.g. ergs per second). luminosity of an object is compared to the solar luminosity, the total energy given off per second by the sun. One solar luminosity is 4 × 1033 ergs per second. Luminosity is denoted as L.

The brightness of a star. Refer Absolute Magnitude and Apparent Magnitude.