what are the factors that contribute to the brightness of a star?
596808
type of star\nspectral type\ndistance from star to Earth
718854
The color at which a star burns has mainly to do with how hot it is burning. The colors roughly range from red (the coolest), organge, green (yes there are green stars), yellow, blue(very hot) and white (the hottest). They give off these colors just like a flame has different colors at different points of the flame. If they give off this color in the spectrum then they would in fact give off those colors of light...but... the closer you are, the brighter it is going to be and the more it will just appear white. If we were closter to our Sun it would appear white to us, and more yellow/orange as we got farther away. \n\nHope this answers your question... =)
1033925
The brightness of a celestial body is relative, a lit match is briter to you than a blazing star because the star is far away. That is why it is relative magnitude.
739943
Very simply: Every element when heated gives off a radiation frequency that is specific to itself. When the entire spectrum of light from a star is analyzed, those frequencies representing specific elements are absorbed and show up as dark lines in specific areas. Each star has a unique pattern. After correcting for any red or blue shift ( discuss that another time), the same elements will appear in the same spectral region.
1145113
This should help you:  http://www.le.ac.uk/physics/faulkes/web/stars/o_st_overview.html
308236
When performing star counts, astronomers consider many different categories which have created been to classify a few stars that have been well studied. One of the hopes of studying the results of star counts is to discover new categories. Different counts typically seek to categorize stars for only a few of the qualities listed below, and determine how common each considered quality is and how stars of that kind are distributed.\n\nTemperature. In astronomy, temperature is usually shown using the letter codes O B A F G K M L T running from blue (type O) through white (type F) to red (type M). Types L and T are used for brown dwarfs, whose 'colors' are in the infrared. \nSize. Size is usually designated by Roman numerals I (supergiants) through V (dwarfs). \nAge. Stars are usually grouped into Population I (young) and Population II (old). \nLocation. In the Milky Way Galaxy the groups are described as thin disk, thick disk, central bulge, and halo. \nMultiplicity. Most stars appear to be members of double star or triple star, or even double-double star systems. Our own sun appears to be rare for not having a companion star. \nThere are many finer subdivisions in all of the above categories.\nIn which category you want me to count the Stars.
604233
By using spectra. Each element has characteristic frequencies of light that it emits or absorbs. If light from the star is spread out into a spectrum (like a rainbow), there will be dark lines for absorbtion and bright lines for emission. By identifying the chemicals that correspond to those lines, we deduce the composition of the star.
471007
Because stars are not very bright. In the day time, scattered sunlight makes the sky a bright blue, brighter than the stars. Even bright streetlights are enough to overwhelm the dim starlight.
17005
Stars seem to "twinkle " because of heat waves in the atmosphere .  They twinkle less in cold weather than in warm .
1029405
You've almost answered your own question:  Stars are "stationary" sources of energy (nuclear) and give off light.  Planets do not and they orbit stars.
789785
The stars themselves don't.  It is just an illusion.  The miles of air in our atmosphere between our eyes and the star changes in temperature and humidity which makes the star look like it is flickering when it really glows at a constant rate.
1095018
Not a simple question, but  this is two main reasons.\n\n1) Brightness of the Star Play a part.   Assume uniform Atmosphere.\n\n2) The Atmosphere also another part.  Assume stars of the same brightness.\n\n1)  Brightness of the Star Play a part.\nBrighter the Star, less likely the twinkle.   Look at the Moon, does it go Bink Bink?  Too Bright.\n\nBut Dimer stars, under the same Atmospheric conditions, may Bink.\n\n2) The Atmosphere also another part.\nThe Atmosphere is not uniform, look at the sky during the day, sometime, it clear blue,  and other time clouds mass abound.\n\nThe Atmosphere is like a thin soup, with some sliver of bread in it,.  using that example, when the Stars of the same brightness is in the Sky,  imagine when a sliver of bread blocks lightly one of the stars, thus one Bink, and another don't.\n\nIt Real life, Stars are not of the same brightness, and the Atmosphere is not always uniform.  making the issue complex.
321927
The color of the star as we perceive it depends on two factors: the intrinsic color of the star and the sensitivity of the human eye. The star can have all kinds of colors from dull red (the coolest stars) via yellow and green to blue (the hottest stars). However, our eye is evolved in the light of the sun and is most sensitive to yellow.\n\nThe result is that we perceive most stars as white, with a few exceptions. Some stars look red, bluish? For instance in the constellation Orion, Betelgeuse is a bright red star at the top left corner, and Rigel is the bright blue star at the bottom right corner. You may want to use binoculars to see the colors more clearly.
1006985
This is an awfully vague question.  I'm guessing that you're asking about how a 3D drawing program calculates the brightness of a given pixel in the final 2D display.  There are really an awful lot of variables to account for in this decision.  There's the distance from the light source, the brightness of that source, the material the light is passing through, the reflectivity of the surface the pixel belongs to, etc.  So there is not really any simple way to calculate intensity.  But the essence of calculating intensity is based on the notion that light intensity decreases according to the square of the distance.  So an object is 1/4 as bright when the distance to the light is doubled.\n\nHope this helps.
874063
You might have seen a planet if it was bright, but also a lot of stars are red.  Cooler stars give off a red color.  There is nothing unusual about it.
892778
I think maybe the separation is smaller than the resolving power of my eyes rather than the angular separation of my eyes. So I can't resolve the two sources and just see one bright star. \n\nBest of luck - Mike
40379
"The star, known as LBV 1806-20, tips the scales of stellar masses at about 150 times the heft of the Sun. It shines up to 40 million times brighter than the Sun. The previous title-holder called the Pistol Star, is a mere six million times brighter than the Sun and weighs about 100 solar masses."