Now the #bbcstargazing hashtag is mostly astrophotographers posting their latest image. This morning the image being retweeted (RT) is this one of M61 taken by Daniel Marlow (@drm3107).
|M61. Credit: Daniel Marlow|
Messier 61, is a bright spiral galaxy in the Southern extremity of the Virgo Cluster (our nearest large cluster of galaxies). It's notable astrophysically for having had 6 supernova observed in it, which apparently ties it with M83 as the Messier galaxy with the most observed supernova, but none of the supernova in M61 have been of the Type1a used to measure cosmological distances.
And the distance to M61 is a bit tricky to estimate. Being near the Virgo cluster whose large mass distorts the usual relationship between recessional velocity and distance you can't really just use the redshift of M61 to give it's distance, and other distance measurements listed in NED for M61 range from about 30 million - 90 million light years (10.1-35.5 Mpc). If it's at the distance of the centre of Virgo it's probably about 50 million light years away (16 Mpc).
Assuming that distance the size of M61 is quite similar to the Milky Way, and so is it's morphology. It's historical classification lists it as a weakly barred Sbc galaxy. It also host an actively accreting black hole in its centre.
Here is the Sloan Digital Sky Survey image of it:
|M61: Credit SDSS|
Links: LookUP on M61; SEDS on M61; NASA Extragalactic Database on M61; Wikipedia on M61.