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	Frequently Asked Questions Send to a friend  Printable version  En Español Keywords   Resources Brightest stars Extrasolar planets Latest news about exoplanets FAQs about Stars and Nebulae Astronomy Gift Shop 2009 Sky Almanac McDonald Observatory logo cap What is the difference between luminosity and brightness?  Luminosity is not the same as brightness. A 100-watt light bulb has a constant luminosity but can appear brighter or fainter depending on how far away it is. A dim star may be dim because it is small, cool, far away, or all three. Other FAQs Select FAQ category Earth, Moon, and the Sun The Solar System Space Probes and Human Exploration Stars and Nebulae Astronomers and Observatories Galaxies and Cosmology Stargazing and Star Lore » FAQs about StarDate Online Stars and Nebulae Links StarDate's Black Hole Encyclopedia Stars and Constellations Virtual Trips to Black Holes and Neutron Stars
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