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A star's real luminosity is proportional to the the square of its diameter, and more or less proportional to the fourth power of its absolute temperature. The star's apparent luminosity is proportional to its real luminosity. It is also inversely proportional to the square of the distance.
Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.
Generally speaking, the apparent luminosity would be an inverse square relationship, which is to say, if the same star was at twice the distance, a quarter of the light would be reaching the observer. But absolute luminosity can of course vary without regard to distance from Earth - dim stars can be close, or bright stars distant, or vice-versa.
It isn't the brightest star - at least, usually Rigel is brighter. However, Betelgeuse is variable, and can sometimes be brighter than Rigel. Wikipedia lists its luminosity as 105,000 times the luminosity of our Sun; and the distance, as 640 light years. Assuming these numbers, this would make it as bright as a star that is 10.5 times as bright as our Sun, at a distance of only 6.4 light years. In other words, the extreme luminosity compensates for its distance.
In that case, both the star's diameter and its luminosity greatly increase.
A star's real luminosity is proportional to the the square of its diameter, and more or less proportional to the fourth power of its absolute temperature. The star's apparent luminosity is proportional to its real luminosity. It is also inversely proportional to the square of the distance.
Based on what? Luminosity, distance or spectral class?
The luminosity depends on what stage of its life cycle the star is in. Also, the apparent luminosity depends on the distance from earth.
How massive it is and its luminosity (the mass and luminosity correlate with each other with most stars, mainly the main sequence stars). The more mass a star has, the shorter its lifespan.
Magnitudes require distance and luminosity. Therefore a specific star is required.
The reference that astronomers use to compare the luminosity of other stars is the sun's luminosity. The luminosity is denoted in multiples of the sun's luminosity. For example, the luminosity of the star Sirius is 25 times the luminosity of the sun.
A star's luminosity is measured according to the relevance to the sun. Basically for example, if a star is 8,300 degrees Celsius and has a luminosity of 0.001; the luminosity is compared to the sun.
Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.Cepheids have a certain relationship between their period, and their absolute luminosity. Thus, their absolute luminosity can be determined. Comparing this with their apparent luminosity allows us to calculate their distance.
Generally, the larger the star, the more luminous it is.However, luminosity is measured as the visible light of a star as seen at the interstellar distance of 10 parsecs.So a massive star could have a lower luminosity than a bright blue supergiant.
Brightness is defined as a correlation between luminosity and distance. So it will depend on what is brighter and what is nearer to us.
The main star in the Polaris system has a luminosity which is 2500 times that of the Sun.
It's luminosity and it's distance from Earth