APOD: A View Toward M101 (2019 Mar 15)

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APOD: A View Toward M101 (2019 Mar 15)

Post by APOD Robot » Fri Mar 15, 2019 4:07 am

Image A View Toward M101

Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way galaxy. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. M101 shares this modern telescopic field of view with more distant background galaxies, foreground stars within the Milky Way, and a companion dwarf galaxy NGC 5474 (lower right). The colors of the Milky Way stars can also be found in the starlight from the large island universe. Its core is dominated by light from cool yellowish stars. Along its grand design spiral arms are the blue colors of hotter, young stars mixed with obscuring dust lanes and pinkish star forming regions. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 23 million light-years away. Its companion NGC 5474 has likely been distorted by its past gravitational interactions with the dominant M101.

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Ann
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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by Ann » Fri Mar 15, 2019 8:06 am

M101 posing as the Milky Way."Copyleft": Henry Norman.
Wikipedia wrote:

M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 258,000[11] light years. It has around a trillion stars, a twice the number in the Milky Way.[12] It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.
I doubt that the diameter of the Milky Way is 258,000 light-years. Maybe the dark matter halo surrounding our galaxy extends that far, but the obviously luminous disk of the Milky Way is hardly more than a bit over 100,000 light-years. The luminous disk of M101 is considered to be 170,000 light-years, and the Pinwheel Galaxy is believed to have twice as many stars as the Milky Way.

This site (written in somewhat shaky English) claims that M101 lacks a supermassive central black hole.
Yet another of interesting Pinwheel Galaxy facts is that there is no central black hole in the galaxy. This is very rare because most galaxies do have a supermassive black hole at the center. Even our Milky Way has one.
Don't take my (or his) word for it. :wink:

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by starsurfer » Fri Mar 15, 2019 12:01 pm

This has always been one of my favourite galaxies.

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by neufer » Fri Mar 15, 2019 1:32 pm

Ann wrote:
Fri Mar 15, 2019 8:06 am
Wikipedia wrote:

M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 258,000 light years. It has around a trillion stars, a twice the number in the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.
I doubt that the diameter of the Milky Way is 258,000 light-years. Maybe the dark matter halo surrounding our galaxy extends that far, but the obviously luminous disk of the Milky Way is hardly more than a bit over 100,000 light-years. The luminous disk of M101 is considered to be 170,000 light-years, and the Pinwheel Galaxy is believed to have twice as many stars as the Milky Way.
https://www.chrisillidgephotos.com/andromeda-galaxy.html wrote: CHRIS ILLIDGE PHOTOS

<<The fall season is the best time for Andromeda Galaxy. It rises in the early evening, and then sets when the sun rises. Andromeda Galaxy is 2.5 million light years away, and it is the closest galaxy to the Milky Way. In this image you can see 2 of Andromeda's dwarf galaxies. The bottom one is M110, and the small blob just above Andromeda is M32. This image is a 2 hour exposure. ​Andromeda Galaxy is a very large galaxy at 220,000 light years in diameter. It's so large in the sky, that it's whole diameter is the same size in the sky as 6 full moons. The reason why we don't see all of that with our eyes is because it's very dim compared to the stars and the moon.>>
Note that at 2.5 million light years away the 220,000 ly diameter Andromeda Galaxy is about 10 full moons in diameter.

There are observable M31 stars & gas orbiting way out there... but they just aren't very impressive.
Art Neuendorffer

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by orin stepanek » Fri Mar 15, 2019 2:40 pm

On a good night you can see the Andromeda! I also noted from time to time, it shows up in night time photos! :wink:
Orin

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by Ann » Fri Mar 15, 2019 3:09 pm

Chris Illidge Photos wrote:

Andromeda Galaxy is 2.5 million light years away, and it is the closest galaxy to the Milky Way.
What about the Large Magellanic Cloud?

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by sillyworm 2 » Fri Mar 15, 2019 3:23 pm

What is the name of the irregular(?) Galaxy at 7:00?

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by bystander » Fri Mar 15, 2019 3:42 pm

Ann wrote:
Fri Mar 15, 2019 3:09 pm
Chris Illidge Photos wrote:
Andromeda Galaxy is 2.5 million light years away, and it is the closest galaxy to the Milky Way.

What about the Large Magellanic Cloud?

And there are at least 15 dwarf galaxies that are even closer.

Satellite Galaxies of the Milky Way
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by sillyworm 2 » Fri Mar 15, 2019 4:49 pm

My comment above....or is it part of M101?

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by MarkBour » Fri Mar 15, 2019 5:17 pm

Ann wrote:
Fri Mar 15, 2019 8:06 am
Wikipedia wrote:

M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 258,000[11] light years. It has around a trillion stars, a twice the number in the Milky Way.[12] It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses.
I doubt that the diameter of the Milky Way is 258,000 light-years. Maybe the dark matter halo surrounding our galaxy extends that far, but the obviously luminous disk of the Milky Way is hardly more than a bit over 100,000 light-years. The luminous disk of M101 is considered to be 170,000 light-years, and the Pinwheel Galaxy is believed to have twice as many stars as the Milky Way.

Ann
I see your point. That estimate of the Milky-way diameter in the Wikipedia article on M101 references a source article that used GAIA data to estimate the Milky Way's mass. And the data source is specifically from globular clusters out in the halo. They don't comment on estimating our galaxy's diameter in the abstract of that article (I did not read the full article). If they do work their way to a diameter of the Milky Way, it is probably one that is quite different than the diameter of our luminous disk as it would be perceived by a distant outside observer.

So, it would seem that the sentence in the Wikipedia article is a poor one, since "by comparison" would be (to use an idiom) a comparison of apples to oranges. Or, possibly, the link is just wrong. Maybe you should post to the article's "Talk" page.
Mark Goldfain

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by MarkBour » Fri Mar 15, 2019 5:31 pm

sillyworm 2 wrote:
Fri Mar 15, 2019 3:23 pm
What is the name of the irregular(?) Galaxy at 7:00?
I'm not very good at this, but looking in SIMBAD, I think it might be NGC 5477.
Mark Goldfain

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by heehaw » Fri Mar 15, 2019 7:21 pm

Just think how much all those astronomers in M101 love OUR galaxy for being RIGHT AT THEIR GALACTIC POLE? And off to one side they see their second-favorite galaxy, Andromeda! Could they clearly see the two Magellanic clouds? I'd have to work to answer that and I am lazy. It will keep; it is not an urgent question...

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by Ann » Fri Mar 15, 2019 7:23 pm

MarkBour wrote:
Fri Mar 15, 2019 5:31 pm
sillyworm 2 wrote:
Fri Mar 15, 2019 3:23 pm
What is the name of the irregular(?) Galaxy at 7:00?
I'm not very good at this, but looking in SIMBAD, I think it might be NGC 5477.
It is.

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Re: APOD: A View Toward M101 (2019 Mar 15)

Post by Boomer12k » Fri Mar 15, 2019 9:37 pm

Really nice wide angle shot. Looks like there was a big merger.

Here is my image of it a few years back with my 10" Meade...more close up of the core area because the camera does not do a wider angle.

2012
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