Object of the Week, April 5th, 2020 - M 105 = NGC 3379 (and friends), in Leo
R.A.: 10h47m49.6s Dec.: +12°34'54" (2000)
Size: 5.0'x 4.6'
Magnitude: 10.20 B; SB 21.7 Mag/arcsec²
M 105 is a giant E1 elliptical galaxy and is part of the Leo I Group, which has between 8 and 24 galaxies, depending on which source you choose to consider, and the entire group lives about halfway to the Virgo Cluster, about 38 million lightyears distant. The other prominent residents of Leo I include M 96, about a degree away, and M 95, an additional half a degree away.
M 105 has the distinction of being the largest Messier elliptical galaxy that is *not* in the Virgo Cluster. It also has a supermassive black hole in its belly that tips the scales at an estimated 50 million solar masses … but according to my research, this only puts it at #9 among its fellow Messier objects in black-hole size, so it is big, but nothing special here.
However, there *is* something strange and wonderful about M 105, which I discovered while looking to learn all about this galaxy. I ran across this 2014 article…
https://medium.com/starts-with-a-ban...5-1e4f3f97bb20
… which caught me completely off-guard and taught me something that I was totally unaware of… it turns out that… “there’s actually a huge halo of neutral gas centered on this galaxy… Whereas our Milky Way has a radius of about 50,000 light-years, the halo of neutral gas surrounding M105 extends for about 650,000 light-years, an incredible distance! Despite being a gas-poor galaxy, there are still more than a billion Suns worth of neutral gas surrounding it, a very large amount.” It seems that M 105 is still producing new star and new star clusters, but at a much-reduced rate of one new star every 10,000 years or so! Who knew? Not me… fascinating stuff!
M 105 AND FRIENDS.jpeg
Observing M 105 is not really much of a challenge, it is a bright elliptical galaxy with no apparent structure and it looks just like every other elliptical galaxy you might choose to observe, but it is in a wonderful field, having a couple of bright companion galaxies in the same field of view, those being NGC 3384, a 10.9 magnitude lenticular galaxy about 7 arcminutes to the northeast and NGC 3389, a 12.5 magnitude Sc spiral galaxy about 10 arcminutes to the southeast. What a wonderful view this is, I could stare at and enjoy these guys for a long time.
I had a lot of fun with this write-up and learned a lot. Perhaps you learned something, too!
As always, give it a go and let us know.
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