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Astronomy/Universe inflation
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Question
Within the context of the inflation of the universe denoted by red shift, are the stars WITHIN particular galaxies moving away from one another, eg stars within our own local (Milky Way) galaxy? Or do the galaxies act as discrete fixed units within the expanding universe?
Your help would be much appreciated. Thank you.
Barry J. Fenton
Hello.
You raise an important question. A relevant point to note is that all objects external to our Local Group of galaxies exhibit redshifts. No individual member galaxies of our group exhibit such shifts. (Individual stars in our galaxy, can - of course, show either red or blue shifts, depending on their relative motion with respect to us at any time - but these must not be confused with *cosmological red shifts* which pertain to the expansion of the universe).
Indeed, some individual galaxies in our Local Group can exhibit blue shifts relative to us. This is explained by virtue of the whole Local Group being a single, gravitationally bound system, sharing the same motion relative to other large gravitationally bound clusters. Individuals, on the other hand, may at given times move toward (blue shift) or away from us in their dynamics.
The key point here, then, is that it is GALAXY CLUSTERS that act as 'discrete fixed units' within the context of the expanding universe. I.e. when we observe expansion and reference this or that red shift, it is relative to particular galaxy clusters. Not particular galaxies, so much - unless they have broken gravitational bonds with a galaxy cluster.
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Answers by Expert:
Philip Stahl
Expertise
I have forty years of experience in Astronomy, specifically solar and space physics. My specialties include the physics of solar flares, sunspots, including their effects on Earth and statistics as applied to astronomical investigations.
Experience
Astronomy: more than forty years experience starting with construction of my own simple telescopes. Worked at university observatory in college, doing astrographic measurements. M.Phil. degree in Physics/Solar Physics and more than ten years as researcher.
Organizations
American Astronomical Society (Solar Physics and Dynamical Astronomy divisions), American Mathematical Society, American Geophysical Union
Publications
Solar Physics (journal), The Journal of the Royal Astronomical Society of Canada, The Proceedings of the Meudon Solar Flare Workshop (1986), The Proceedings of the Caribbean Physics Conference (1985). Books: 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level'.
Education/Credentials
B.A. Astronomy, M. Phil. Physics
Awards and Honors
American Astronomical Society Studentship Award (1984), Barbados Government Award for Solar Research
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