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20. Galaxy Interaction and Motion
متوسط طول الصوت:
65 seconds
الإنجليزية
الولايات المتحدة
29 حلقة
منذ 26 يوليو، 2011
episodic
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Transcript: In cosmology galaxies are used as markers of expanding space. In addition to the overall cosmic expansion gravity has caused matter to clump or cluster on many different scales. In addition to the gravitational attraction that caused galaxies to collapse and form in the first place gr…
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Transcript: Most of the techniques for measuring distance in astronomy depend on well understood properties of stars or entire galaxies. However, if astronomers believe they’ve measured the current expansion rate of the universe then redshift itself can be used to indicate distance. Redshift is d…
Transcript: When a massive star dies the supernova that results can rival an entire galaxy in brightness, so it can be seen to a very large distance, a billion lightyears or more. When a single massive star dies it does not do so in a well regulated way, but the supernovae that result from a binar…
Transcript: A clever technique for measuring the distance of galaxies that applies to galaxies with smooth light distributions like ellipticals is called surface brightness fluctuations. The idea of surface brightness is that it is the flux per unit area in a galaxy. The important thing to realiz…
Transcript: One of the best distance indicators for elliptical galaxies is the Faber-Jackson relation, named after the two astronomers who discovered it. The Faber-Jackson relation relates the range of stellar velocities or their velocity dispersion in the nucleus in an elliptical galaxy with the …
Transcript: An important distance indicator for spiral galaxies is called the Tully-Fisher relation, named after the two astronomers that discovered it. Observationally the luminosity of spiral galaxies is correlated with their rotation speed of their gas disks. There’s a physical basis for this …
Transcript: Beyond a distance of about twenty megaparsecs, or sixty or seventy million lightyears, it becomes difficult to use individual stars as distance indicators. Cepheid variables are hopelessly blurred in the summed light of billions of stars in the distant galaxy, and even supernovae, whic…
Transcript: In the nearby universe astronomers primarily use stars as distance indicators. Cepheid variables which were classically used by Hubble to demonstrate the distance to the nebulae and the universal expansion are still used. As luminous stars with well understood physics they can be foun…
Transcript: The Hubble constant sets the current expansion rate of the universe and gives an indication of its size and age. The best currently measured value of the Hubble constant comes from a heroic project done with the Hubble Space Telescope over a number of years. The Hubble Space Telescope…
Transcript: If we assume that the cosmic expansion has been uniform we can use the current value of the Hubble constant to get an estimate of the edge of the universe. Velocity is the same as distance times time, and the Hubble relation states that the velocity is equal to the Hubble constant time…
إخلاء المسؤولية: البودكاست والأعمال الفنية المضمنة في هذه الصفحة مأخوذة من Dr. Christopher D. Impey, Professor, Astronomy، وهي مملوكة لمالكها وليست تابعة لشركة Listen Notes, Inc أو معتمدة منها.
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