Modern research - rotating gas. This galaxy rotation...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Modern research Rotation curve of a typical spiral galaxy: predicted (A) and observed (B). The distance is from the galactic core. The second most distant galaxy: UDFy-38135539 In 1944, Hendrik van de Hulst predicted microwave radiation at a wavelength of 21 cm resulting from interstellar atomic hydrogen gas; [42] this radiation was observed in 1951. The radiation allowed for much improved study of the Milky Way Galaxy, since it is not affected by dust absorption and its Doppler shift can be used to map the motion of the gas in the Galaxy. These observations led to the postulation of a rotating bar structure in the center of the Galaxy. [43] With improved radio telescopes , hydrogen gas could also be traced in other galaxies. In the 1970s it was discovered in Vera Rubin 's study of the rotation speed of gas in galaxies that the total visible mass (from the stars and gas) does not properly account for the speed of the
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rotating gas. This galaxy rotation problem is thought to be explained by the presence of large quantities of unseen dark matter . [44] [45] Beginning in the 1990s, the Hubble Space Telescope yielded improved observations. Among other things, it established that the missing dark matter in our galaxy cannot solely consist of inherently faint and small stars. [46] The Hubble Deep Field , an extremely long exposure of a relatively empty part of the sky, provided evidence that there are about 125 billion (1.2510 11 ) galaxies in the universe. [47] Improved technology in detecting the spectra invisible to humans (radio telescopes, infrared cameras, and x-ray telescopes ) allow detection of other galaxies that are not detected by Hubble. Particularly, galaxy surveys in the Zone of Avoidance (the region of the sky blocked by the Milky Way) have revealed a number of new galaxies...
View Full Document

Ask a homework question - tutors are online