Hubble stars overlay over light fixtures10/28/2023 ![]() In astronomy, accretion is the process of growing a massive object by gravitationally attracting less massive objects. Recent observations of distant supernova explosions suggest that we may live in an accelerating universe. Each chemical element emits and absorbs radiated energy at specific wavelengths, making it possible to identify the elements present in the atmosphere of a star or other celestial body by analyzing which absorption lines are present.Ī model for the universe in which a repulsive force counteracts the attractive force of gravity, driving all the matter in the universe apart at speeds that increase with time. After the starlight passes through the cloud, dark lines called absorption lines appear in the star’s continuous spectrum at wavelengths corresponding to the light-absorbing elements.Ī dark line in a continuous spectrum caused by absorption of light. For example, a gas cloud can absorb starlight that passes through it. The process by which light transfers its energy to matter. On the Kelvin temperature scale, this temperature is the zero-point (0 K), which is equivalent to -273☌ and -460☏. The coldest possible temperature, at which all molecular motion stops. However, if both objects were placed at the same distance from us, Rigel would appear much brighter than our Sun because its absolute brightness is much larger. For example, the apparent brightness of our Sun is much greater than that of the star Rigel in the constellation Orion because it is so close to us. The absolute brightness or magnitude of an object is the apparent brightness or magnitude it would have if it were located exactly 32.6 light-years (10 parsecs) away. Four Successful Women Behind the Hubble Space Telescope's AchievementsĪ measure of the true brightness of an object.Characterizing Planets Around Other Stars.Measuring the Universe's Expansion Rate. ![]()
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