Starship Asterisk*

Galaxy Wars: M81 and M82

Explanation: These two galaxies are far far away, 12 million light-years distant toward the northern constellation of the Great Bear. On the left, with grand spiral arms and bright yellow core is spiral galaxy M81, some 100,000 light-years across. On the right marked by red gas and dust clouds, is irregular galaxy M82. The pair have been locked in gravitational combat for a billion years. Gravity from each galaxy has profoundly affected the other during a series of cosmic close encounters. Their last go-round lasted about 100 million years and likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. M82 was left with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. In the next few billion years, their continuing gravitational encounters will result in a merger, and a single galaxy will remain.

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"Locked in gravitational combat," really? So tired of the overuse of war metaphors especially when another would be so easy to find. "They've been dancing together for a billion years - spurring creation and complexity in one another, someday to unite." "They've been sliding around their mutual center of mass like two marbles circling in a funnel." "Their motion through space is like trying to draw a Spirograph pattern using two markers on the same gear-wheel at once - a gear whose size will decrease over millions of years until their patterns overlap." If I can generate three non-war metaphors in two minutes at 1 AM with zero experience writing APOD captions, I bet you can do much better.

Now that I've prodded you on a detail, though, thank you for all the work you do on APOD. The images are beautiful and it's very restoring after a long day of news to contemplate something huge, old, far-away and amazing.

I always think of M81 and M82 as two members of a galactic triplet, which includes galaxy NGC 3077. The picture at right shows how the three galaxies are connected with streams of neutral hydrogen.

You can really see how the tidal forces between M81 and NGC 3077 (far left) help create the sleek, two-armed spiral shape of M81.




















M81 and the famous Whirlpool galaxy, M51, are both grand design galaxies, which is to say that they have two all-dominant spiral arms. Interestingly, it is probable that they got their grand design spiral shapes by interacting with other galaxies, M51 with NGC 5195, and M82 with both NGC 3077 and M82.

Note how different M81 and M51 are as spiral galaxies. The arms of M51 are long, thick, bright, convoluted and full of star formation, while the arms of M81 are short, rather thin, sleek, not so bright and not very rich in star formation. Also note that M51 has a small yellow bulge, whereas the bulge of M81 is really large. But a similarity between these two galaxies is that both are unbarred.

No Hα filter was used for the Hubble image of M81, so the red emission nebulas of M81 don't stand out. They are however much smaller and fewer than the emission nebulas of M51. Check out a Hubble closeup of a part of M81 here.





















Finally, let's take a look at the too rarely photographed galaxy NGC 3077, which interacts with M81 and helps give it its grand design shape. Outwardly, NGC 3077 looks like a typical all yellow dwarf elliptical galaxy. But it's got a fiery heart, burning blue from raging star formation.

There are some interesting similarities between NGC 3077 and M82, the famous "red-gas-spitting" neighboring galaxy of M81. Both M82 and NGC 3077 have stopped forming stars almost everywhere except in their cores, which, however, are ablaze with brilliant star formation. Clearly interactions with M81 have forced almost all the gas of NGC 3077 and M82 into the cores of these two galaxies, causing a wildfire of star formation there.

Call the fire brigade!

Ann

noclevernametonight wrote: ↑Fri May 15, 2020 5:57 am "Locked in gravitational combat," really? So tired of the overuse of war metaphors especially when another would be so easy to find. "They've been dancing together for a billion years - spurring creation and complexity in one another, someday to unite." "They've been sliding around their mutual center of mass like two marbles circling in a funnel." "Their motion through space is like trying to draw a Spirograph pattern using two markers on the same gear-wheel at once - a gear whose size will decrease over millions of years until their patterns overlap." If I can generate three non-war metaphors in two minutes at 1 AM with zero experience writing APOD captions, I bet you can do much better.

Now that I've prodded you on a detail, though, thank you for all the work you do on APOD. The images are beautiful and it's very restoring after a long day of news to contemplate something huge, old, far-away and amazing.

With such a wonderful constellation, we shouldn't actually criticize but simply perceive it in astonishment. But I think the argument is justified. It would be better to speak of collision. War is a strong word, especially when I search for pictures under M82 and only find rifles on the web. Maybe it would be better to write Messier and to indicate the NGC name at the same time.

Ah! Don't they make a lovely couple!

"There are some interesting similarities between NGC 3077 and M82, the famous "red-gas-spitting" neighboring galaxy of M81. Both M82 and NGC 3077 have stopped forming stars almost everywhere except in their cores, which, however, are ablaze with brilliant star formation. Clearly interactions with M81 have forced almost all the gas of NGC 3077 and M82 into the cores of these two galaxies, causing a wildfire of star formation there."

ThanX Ann, very interesting note.
... here is another picture of the core of NGC 3077...


https://www.flickr.com/photos/deealexan ... otostream/




Jac from the AVAO Team

Very beautiful image

Where’s NGC 3077? It seems to have been playing with its galactic big siblings as well.

I was pleasantly surprised the first time I got all three of them in the eyepiece together.

Cousin Ricky wrote: ↑Fri May 15, 2020 2:08 pm Where’s NGC 3077? It seems to have been playing with its galactic big siblings as well.

Looking through the comments, I see I’m not the only one who missed NGC 3077.

noclevernametonight wrote: ↑Fri May 15, 2020 5:57 am "Locked in gravitational combat," really? So tired of the overuse of war metaphors especially when another would be so easy to find. "They've been dancing together for a billion years - spurring creation and complexity in one another, someday to unite." "They've been sliding around their mutual center of mass like two marbles circling in a funnel." "Their motion through space is like trying to draw a Spirograph pattern using two markers on the same gear-wheel at once - a gear whose size will decrease over millions of years until their patterns overlap." If I can generate three non-war metaphors in two minutes at 1 AM with zero experience writing APOD captions, I bet you can do much better.

Now that I've prodded you on a detail, though, thank you for all the work you do on APOD. The images are beautiful and it's very restoring after a long day of news to contemplate something huge, old, far-away and amazing.

These are Americans. The language of violence is in the ether here; we don’t even think about it.

AVAO wrote: ↑Fri May 15, 2020 11:54 am "There are some interesting similarities between NGC 3077 and M82, the famous "red-gas-spitting" neighboring galaxy of M81. Both M82 and NGC 3077 have stopped forming stars almost everywhere except in their cores, which, however, are ablaze with brilliant star formation. Clearly interactions with M81 have forced almost all the gas of NGC 3077 and M82 into the cores of these two galaxies, causing a wildfire of star formation there."

ThanX Ann, very interesting note.
... here is another picture of the core of NGC 3077...


https://www.flickr.com/photos/deealexan ... otostream/




Jac from the AVAO Team

Thank, Jac, that's a very nice image! I much appreciate being able to see the Hα in the core of NGC 3077.

I'm also very glad to see that the picture was taken by a woman, Hypatia Alexandria!

Ann

It is so difficult for me to understand or even grasp how 2 galaxies separated by at least 150,000 light years have any gravitational effect on each other. Such an incredible mass that is unfathomable by this tiny spec of flesh sitting on Earth

Feeling quite insignificant in North Idaho,

Jer

M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

APOD Robot wrote: ↑Fri May 15, 2020 4:06 am
Explanation: ....Their last go-round lasted about 100 million years....

Just curious how they could know such a detail? And if just their last interaction lasted that long (presumably when they were closest?), and these two galaxies are gradually spiraling toward each other, I would think it would take much longer than a few billion years to merge.

"Thank, Jac, that's a very nice image! I much appreciate being able to see the Hα in the core of NGC 3077.
I'm also very glad to see that the picture was taken by a woman, Hypatia Alexandria!
Ann"

Indeed. This is true today as in the past. In honor of ...

Hypatia from Alexandria (Greek Ὑπατία Hypatía; * around 355 in Alexandria; † March 415 or March 416 in Alexandria) was a Greek / Hellenistic Neoplatonist philosopher, astronomer, and mathematician, who lived in Alexandria, Egypt, then part of the Eastern Roman Empire. She was a prominent thinker of the Neoplatonic school in Alexandria where she taught philosophy and astronomy. She is the first female mathematician whose life is reasonably well recorded. https://en.wikipedia.org/wiki/Hypatia

Jac

Hm, M82 looks more like a distorted spiral galaxy than an irregular one.

AVAO wrote: ↑Fri May 15, 2020 10:32 am With such a wonderful constellation, we shouldn't actually criticize but simply perceive it in astonishment. But I think the argument is justified. It would be better to speak of collision. War is a strong word, especially when I search for pictures under M82 and only find rifles on the web. Maybe it would be better to write Messier and to indicate the NGC name at the same time.

The exact same thing happened to me. So I put a "galaxy" behind it...

AVAO wrote: ↑Fri May 15, 2020 10:32 am

noclevernametonight wrote: ↑Fri May 15, 2020 5:57 am "Locked in gravitational combat," really? So tired of the overuse of war metaphors especially when another would be so easy to find. "They've been dancing together for a billion years - spurring creation and complexity in one another, someday to unite." "They've been sliding around their mutual center of mass like two marbles circling in a funnel." "Their motion through space is like trying to draw a Spirograph pattern using two markers on the same gear-wheel at once - a gear whose size will decrease over millions of years until their patterns overlap." If I can generate three non-war metaphors in two minutes at 1 AM with zero experience writing APOD captions, I bet you can do much better.

Now that I've prodded you on a detail, though, thank you for all the work you do on APOD. The images are beautiful and it's very restoring after a long day of news to contemplate something huge, old, far-away and amazing.

With such a wonderful constellation, we shouldn't actually criticize but simply perceive it in astonishment. But I think the argument is justified. It would be better to speak of collision. War is a strong word, especially when I search for pictures under M82 and only find rifles on the web. Maybe it would be better to write Messier and to indicate the NGC name at the same time.

I like noclevernametonight's comment and agree with it being justified. At times I've also even objected to the word "collision" with regard to galactic interactions. Collision has a destructive connotation, while in reality, what is destined to happen is a merger that will induce star formation and the creation of a larger galaxy. More like a marriage than a war, if a metaphor is needed.

Bruce

AVAO wrote: ↑Fri May 15, 2020 3:53 pm "Thank, Jac, that's a very nice image! I much appreciate being able to see the Hα in the core of NGC 3077.
I'm also very glad to see that the picture was taken by a woman, Hypatia Alexandria!
Ann"

Indeed. This is true today as in the past. In honor of ...

Hypatia from Alexandria (Greek Ὑπατία Hypatía; * around 355 in Alexandria; † March 415 or March 416 in Alexandria) was a Greek / Hellenistic Neoplatonist philosopher, astronomer, and mathematician, who lived in Alexandria, Egypt, then part of the Eastern Roman Empire. She was a prominent thinker of the Neoplatonic school in Alexandria where she taught philosophy and astronomy. She is the first female mathematician whose life is reasonably well recorded. https://en.wikipedia.org/wiki/Hypatia

Jac

Yes, I have heard of Hypatia of Alexandria, so I knew that "Hypatia Alexandria" had to be an alias.

But a very well-chosen and honorable one!

Ann

JohnD wrote: ↑Fri May 15, 2020 3:28 pm M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

I don't think we know if the violence in the center of M82 is going to make the entire galaxy uninhabitable.

Chris, any thoughts?

Ann

JohnD wrote: ↑Fri May 15, 2020 3:28 pm M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

I wonder about that too. But couldn't atmospheres of planets in M82 shield them from x-rays?

Ann wrote: ↑Fri May 15, 2020 4:49 pm

JohnD wrote: ↑Fri May 15, 2020 3:28 pm M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

I don't think we know if the violence in the center of M82 is going to make the entire galaxy uninhabitable.

Chris, any thoughts?

Ann

I doubt complex life is present in galaxies except in their discs, far from the central bulge, or in their outlying regions if they're not spirals. No doubt there are regions in colliding galaxies that lose their long term stability, which is probably doomsday for complex life. But I think far more areas go on largely unaffected.

And those outlying areas cover an unimaginably immense area.( You can put a number to it yes).Plenty of room for LIFE out there.

Ann wrote: ↑Fri May 15, 2020 4:49 pm

JohnD wrote: ↑Fri May 15, 2020 3:28 pm M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

I don't think we know if the violence in the center of M82 is going to make the entire galaxy uninhabitable.

Chris, any thoughts?

Ann

A lot can change in 12,000,000 Years But Shucks It would be an awful long trip just to find out! :

orin stepanek wrote: ↑Fri May 15, 2020 9:10 pm

Ann wrote: ↑Fri May 15, 2020 4:49 pm

JohnD wrote: ↑Fri May 15, 2020 3:28 pm M82 has "colliding gas clouds so energetic the galaxy glows in X-rays."

At a distance of 12 million LYs, it's a bit academic, but strike that one off the list for potential life, then?
John

I don't think we know if the violence in the center of M82 is going to make the entire galaxy uninhabitable.

Chris, any thoughts?

Ann

A lot can change in 12,000,000 Years :mrgreen: But Shucks It would be an awful long trip just to find out! : :wink:

Actually, between those two, practically nothing is going to change at all in just 12 million years. They're interacting on a time scale of billions of years.

Chris Peterson wrote: ↑Fri May 15, 2020 9:12 pm

orin stepanek wrote: ↑Fri May 15, 2020 9:10 pm

Ann wrote: ↑Fri May 15, 2020 4:49 pm

I don't think we know if the violence in the center of M82 is going to make the entire galaxy uninhabitable.

Chris, any thoughts?

Ann

A lot can change in 12,000,000 Years But Shucks It would be an awful long trip just to find out! :

Actually, between those two, practically nothing is going to change at all in just 12 million years. They're interacting on a time scale of billions of years.

I'm sure you're correct; -> you usually are; but I was talking about the X-rays and not the dance! they could be on a billions of years thingy also! I don't think i'll wait around to find out!