Alpha Centauri and the sun
alpha centari and the sun
Blue Supergiants and Supergiants
In astronomy, Luminosity is the amount of energy a body radiates per unit time. The luminosity of stars is measured in two forms: apparent (counting visible light only) and bolometric (total radiant energy); a bolometer is an instrument that measures radiant energy over a wide band by absorption and measurement of heating. When not qualified, luminosity means bolometric luminosity, which is measured in the SI units watts, or in terms of solar luminosities, ; that is, how many times as much energy the object radiates than the Sun, whose luminosity is 3.846×1026 W. Luminosity is an intrinsic constant independent of distance, and is measured as absolute magnitude corresponding to apparent luminosity, or bolometric magnitude corresponding to bolometric luminosity. In contrast, apparent brightness is related to distance by an inverse square law. Visible brightness is usually measured by apparent magnitude, which is on a logarithmic scale. In measuring star brightnesses, visible luminosity (not total luminosity at all wave lengths), apparent magnitude (visible brightness), and distance are interrelated parameters. If you know two, you can determine the third. Since the sun's luminosity is the standard, comparing these parameters with the sun's apparent magnitude and distance is the easiest way to remember how to convert between them.
surface temperature and luminosity
First let's assume the question is about a star's actual brightness not apparent brightness as seen from Earth. There are in fact several possibilities. The Hertzprung-Russell diagram is helpful here. One possibility is red dwarfs and white dwarfs. Of course there's large variation within these groups, but a red dwarf can certainly have a luminosity that's similar to a white dwarf. If the question is about apparent brightness, then a distant luminous star can appear similar in brightness to a nearby faint star.
alpha centari and the sun
If the binary stars were of too high luminosity it would be impossible to distinguish the two through vision alone. Therefore most visual binary stars are of low luminosity.
The star that is hotter will have a higher luminosity.
The star that is hotter will have a higher luminosity.
The luminosity depends on what stage of its life cycle the star is in. Also, the apparent luminosity depends on the distance from earth.
Their distance away from you and their intrinsic luminosity.
Blue Supergiants and Supergiants
The two most common elements in the Universe, and in most stars are - in that order - hydrogen and helium (elements #1 and #2).
In astronomy, Luminosity is the amount of energy a body radiates per unit time. The luminosity of stars is measured in two forms: apparent (counting visible light only) and bolometric (total radiant energy); a bolometer is an instrument that measures radiant energy over a wide band by absorption and measurement of heating. When not qualified, luminosity means bolometric luminosity, which is measured in the SI units watts, or in terms of solar luminosities, ; that is, how many times as much energy the object radiates than the Sun, whose luminosity is 3.846×1026 W. Luminosity is an intrinsic constant independent of distance, and is measured as absolute magnitude corresponding to apparent luminosity, or bolometric magnitude corresponding to bolometric luminosity. In contrast, apparent brightness is related to distance by an inverse square law. Visible brightness is usually measured by apparent magnitude, which is on a logarithmic scale. In measuring star brightnesses, visible luminosity (not total luminosity at all wave lengths), apparent magnitude (visible brightness), and distance are interrelated parameters. If you know two, you can determine the third. Since the sun's luminosity is the standard, comparing these parameters with the sun's apparent magnitude and distance is the easiest way to remember how to convert between them.
A binary star consists of two stars gravitationally locked together in a mutual orbit. If the plane of that orbit is in line with us, as observers, then occasionally, one star will eclipse the other, producing a change in luminosity as one star is briefly blocked from view.
The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. its luminosity (intrinsic brightness or absolute magnitude). On it, astronomers plot stars' color, temperature, luminosity, spectral type, and evolutionary stage. This diagram shows that there are 3 very different types of stars:Most stars, including the sun, are "main sequence stars," fueled by nuclear fusion converting hydrogen into helium. For these stars, the hotter they are, the brighter. These stars are in the most stable part of their existence; this stage generally lasts for about 5 billion years.As stars begin to die, they become giants and supergiants (above the main sequence). These stars have depleted their hydrogen supply and are very old. The core contracts as the outer layers expand. These stars will eventually explode (becoming a planetary nebula or supernova, depending on their mass) and then become white dwarfs, neutron stars, or black holes (again depending on their mass).Smaller stars (like our Sun) eventually become faint white dwarfs (hot, white, dim stars) that are below the main sequence. These hot, shrinking stars have depleted their nuclear fuels and will eventually become cold, dark, black dwarfs.
Hydrogen and helium are the most abundant elements in stars.