you don't know who she is but she is dead:

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you don't know who she is but she is dead:

Post by pravalika nanda on Tue Dec 27, 2016 6:16 pm

In 1933, Swiss astronomer Fritz Zwicky observed the Coma Cluster, a galaxy cluster roughly 50 million light-years across that’s filled with thousands of galaxies. He found that these galaxies move so rapidly through the cluster that it ought to fly apart. There simply wasn’t enough visible matter to hold the galaxy cluster together with its constituents zipping through it that fast. Yet the cluster was stable.

Zwicky decided there must be a hidden ingredient, which he called dunkle Materie, or “dark matter,” that held the cluster together.

The issue remained relatively quiet for the next three decades. It was Rubin, Ford, and their colleagues who gathered further evidence that individual galaxies also did not rotate as expected. Because most galaxies have a luminous central bulge composed of densely packed stars, and faint outskirts composed of far fewer stars, astronomers had largely assumed that most of a galaxy’s mass was concentrated in the center. The natural conclusion then is that galaxies should rotate much as our solar system does, where the inner planets orbit the Sun faster than the outer planets

But the team’s work showed that wasn’t the case. In their 1978 Astrophysical Journal letter, the astronomers looked at the galactic rotation curves — graphs showing the orbital speeds of stars versus their distance from the galactic center — of 10 galaxies (seven are shown at right). If the visible matter was the only character in this story, then these curves would dip down at large distances, much like it does for the solar system.

Instead, all the rotation curves are relatively flat. The stars far from the centers of galaxies, in the sparsely populated fringes, rotate just as rapidly as the stars closer in. The team’s calculations showed that galaxies must contain about 10 times as much dark matter as light matter.

pravalika nanda

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Re: you don't know who she is but she is dead:

Post by garam_kuta on Tue Dec 27, 2016 10:23 pm

thanks for posting this.


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