- #1
AJH
- 14
- 0
I have found M81 and M82 with my 10x50 binoculars. I understand that they are both part of the M81 group, separate from our own Local Group, and was under the impression that anything outside of our Local Group (including the Virgo cluster and other groups) was receding from us due to the general expansion of space overcoming gravity at greater distances.
I have read that M81 emits light with a negative red shift whereas other galaxies in the M81 Group (including M82) emit radiation with positive red shifts and that this might be due to M81 alone happening to be temporarily approaching us as part of its rotation around a galactic-group gravitational centre. If so, should at least some of the many other galaxies in the group also be approaching us and displaying negative redshifts? Are we just deducing that M81 is ultimately receding from us due to that trend in neighbouring galaxies? I have come across a recessional velocity for M81 of 95 km/sec quoted a couple of times and wonder how this is arrived at.
I find M81 and M82 more interesting objects to view than M33 (for instance) and would like to know when I look at them if both or either are moving away from us.
I have read that M81 emits light with a negative red shift whereas other galaxies in the M81 Group (including M82) emit radiation with positive red shifts and that this might be due to M81 alone happening to be temporarily approaching us as part of its rotation around a galactic-group gravitational centre. If so, should at least some of the many other galaxies in the group also be approaching us and displaying negative redshifts? Are we just deducing that M81 is ultimately receding from us due to that trend in neighbouring galaxies? I have come across a recessional velocity for M81 of 95 km/sec quoted a couple of times and wonder how this is arrived at.
I find M81 and M82 more interesting objects to view than M33 (for instance) and would like to know when I look at them if both or either are moving away from us.