Astronomy 1021 Lecture 37: Dark Matter + Dark Energy

• School: Western University
• Department: Astronomy
• Course: Astronomy 1021
• Professor: Robert Cockcroft

Document Summary

Is there anything more in the universe that we (cid:272)a(cid:374)"t see: yes, remember dark matte, we(cid:859)ll (cid:396)e(cid:448)isit the (cid:272)ase fo(cid:396) dark matter, later we will also talk about something quite different, which is dubbed dark energy. Rotation curves: rotation curves are how we detected the dark matter problem, we use them to measure the mass of galaxies. Mass of the milky way: for galaxies, we would expect the velocities to go down for stars near the outer edge (curve b, but this is not what we see, mw rotation curve. So, there must be much more mass farther out in the mw than we can see: total visible mass in the milky way: 200 billion solar masses: total mass deduced from rotation curve: 1 trillion solar masses: either our understanding of gravity is not complete (a minority of astronomers hold this view) or most of the mass is not emitting any kind of light: dark matter.