what factors determine the brightness of a star?
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However, the brightness of a star depends on its composition and how far it is from the planet. Astronomers define star brightness in terms of apparent magnitude — how bright the star appears from Earth — and absolute magnitude — how bright the star appears at a standard distance of 32.6 light-years, or 10 parsecs.
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absolute brightness: The apparent brightness a star would have if it were placed at a standard distance of 10 parsecs from Eart. Page 1. A. absolute brightness: The apparent brightness a star would have if it were placed at a standard distance of 10 parsecs from Earth.
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When I say apparent brightness, I mean how bright the star appears to a detector here on Earth. The luminosity of a star, on the other hand, is the amount of light it emits from its surface. The difference between luminosity and apparent brightness depends on distance.
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The surface temperature of a star determines the color of light it emits. Blue stars are hotter than yellow stars, which are hotter than red stars.
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Fast exposure times means they can get good pictures of the bright Earth or lunar surface, but it also means no stars in the picture. Even in space, stars are relatively dim, and simply don't produce enough light to show up in photos set for bright sunlight.
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['It must orbit a star (in our cosmic neighborhood, the Sun).', 'It must be big enough to have enough gravity to force it into a spherical shape.', 'It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.']
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['A flat, rotating disc of stars and interstellar matter of which spiral arms are prominent components.', 'A central stellar bulge of mainly older stars, which resembles an elliptical galaxy.', 'A bar-shaped distribution of stars.']
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A star's brightness, or luminosity, depends on the star's surface temperature and size. If two stars have the same surface temperature, the larger star will be more luminous.
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Brightness-Luminosity Relationship: At a particular Luminosity, the more distant an object is, the fainter its apparent brightness becomes as the square of the distance.
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Life Cycles of Stars. A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born.
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For instance, the color of a star – which varies from bluish-white and yellow to orange and red – is primarily due to its composition and effective temperature. And at all times, stars emit light which is a combination of several different wavelengths. On top of that, the color of a star can change over time.
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['Light intensity.', 'Carbon dioxide concentration.', 'Temperature. It is useful to be able to interpret a graph like the example below.']
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A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust from which it was born.
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The greater the mass of a main sequence star, the greater its effective temperature. This, combined with the larger radius of higher mass main sequence stars accounts for their much greater luminosity. Remember, L ∝ T4 and L ∝ R2 so even a small increase in effective temperature will significantly increase luminosity.
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The total energy emitted per second by a star is called its luminosity. How bright a star looks from the perspective of Earth is its apparent brightness. The apparent brightness of a star depends on both its luminosity and its distance from Earth.
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The luminosity of a star, on the other hand, is the amount of light it emits from its surface. The difference between luminosity and apparent brightness depends on distance. ... So, everyone will measure a different apparent brightness for the same star if they are all different distances away from that star.
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Planets appear brighter than stars due to their relative proximity to the primary light source (the Sun) and to ourselves. The planets themselves (except for Earth) emit no light of their own; they simply reflect the light of the sun.