APOD: Starburst Galaxy M94 (2015 May 26)

[APOD Robot]

Starburst Galaxy M94

Explanation: What could cause the center of M94 to be so bright? Spiral galaxy M94 has a ring of newly formed stars surrounding its nucleus, giving it not only an unusual appearance but also a strong interior glow. A leading progenitor hypothesis holds that an elongated knot of stars known as a bar rotates in M94 and has generated a burst of star formation in the inner ring. Recent observations have revealed the outer, fainter ring is not closed and relatively complex. M94, pictured here spans about 30,000 light years, lies about 15 million light years away, and can be seen with a small telescope toward the constellation of the Hunting Dogs (Canes Venatici).

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[Ann]

Well, I can't help it. This is eye candy to me. What a stunning beauty! Congratulations, Leonardo Orazi, I love your images!

The galaxy is only 30,000 light years across? That makes it pretty small, and considerably smaller than the Milky Way, doesn't it? And is it only 15 million light years away? I had no idea that it was so nearby.

Ann

[Beyond]

That's one good looking galaxy! I'm glad we're able to see it about straight on. The most unusual link, is most unusual. It looks as if a panda and a dog were well acquainted with each other.

[starsurfer]

This is a pretty cool galaxy! What's more interesting is that the outer ring has been known for less than 20 years and I think might have been discovered by the amateur astrophotographer R. Jay GaBany. If you look carefully, you can see some small star clusters, starclouds and nebulae in the outer ring as well as the central part. Has anyone ever taken a Ha image of this galaxy?

[Ann]

This is a pretty cool galaxy! What's more interesting is that the outer ring has been known for less than 20 years and I think might have been discovered by the amateur astrophotographer R. Jay GaBany. If you look carefully, you can see some small star clusters, starclouds and nebulae in the outer ring as well as the central part. Has anyone ever taken a Ha image of this galaxy?

Great work by GaBany!

Interestingly, there are some similarities between M94 and M77, although M77 is a much larger galaxy with an active core. One of the similarities is that M77 also has widespread outer arms with star formation.

Ann

[star-struk]

what hills and valleys

glades and fields

grace these winding arms

[Leonardo]

Many Thanks for pubblication to APOD Editors and Staff and thanks Ann for your nice comment.

All the best,
Leo

[BMAONE23]

http://www.cosmotography.com/images/sma ... ement.html
Here is a different observation from Spitzer
Science Blogs also has some interesting images at varying wavelengths
http://scienceblogs.com/startswithabang ... alaxy-m94/

[NGC3314]

In H-alpha, the most striking feature of M94 is a tight ring of H II regions just at the boundary where the surface brightness of spiral structure changes. Here is an old continuum-subtracted) image in pseudo color:

(Historical "grumpy old astronomer" note - I'm pretty sure the existence of the outer ring (although not its detailed structure) was noted by Sandage in the Hubble Atlas, and there are literature references to it from the 1970s, but I can't double-check at the moment since my copy is at home).

[Ann]

Very interesting, BMAONE23 and NGC3314!

Ann

[geckzilla]

I think this object is a good example of a spiral transitioning to a lenticular. The continuous rings and the tight nuclear structures seem common in lenticular galaxies and yet the spiral structures are still evident enough for most people to say it's a spiral.

[hoohaw]

To me it would be interesting to have a photo like this one treated to remove all the foreground stars. Never thought of that before! We've never seen a galaxy "as it is," there's always neighborhood rubbish in between.

[Boomer12k]

Very interesting...
If there were lesser photography, and no details about the outer ring, seeing that the inner portion, (being observed as the ONLY portion), rotated at the same rate....this might lead to the postulate of there being more Mass somewhere....

Looks like the ending phases of a merger....the other galaxy got splayed all over the place, now is forming up...

Really great pic!
:---[===] *

[geckzilla]

To me it would be interesting to have a photo like this one treated to remove all the foreground stars. Never thought of that before! We've never seen a galaxy "as it is," there's always neighborhood rubbish in between.

There are many examples of galaxies without interloping Milky Way stars. If you look away from the galactic plane there are many of them out there. I've got dozens of examples I've pulled out of the Hubble archive. Thousands, if you count the myriad of background galaxies and clusters of galaxies.

[Ann]

I think this object is a good example of a spiral transitioning to a lenticular. The continuous rings and the tight nuclear structures seem common in lenticular galaxies and yet the spiral structures are still evident enough for most people to say it's a spiral.

Interesting observation. I think it is time to compare M94 with yet another galaxy, NGC 4314. This Hubble picture shows the rather small star forming nuclear ring of NGC 4314, and the inset shows the large barred spiral galaxy in its entirety. There is no star formation in NGC 4314 at all apart from the nuclear ring. This (blurry) picture gives you an idea of what the nuclear ring looks like in relation to the galaxy as a whole. Although NGC 4314 has a very clear and obvious barred spiral structure, it is definitely on its way to becoming a lenticular galaxy. But first it might pass through transitional stages, like NGC 7743. That galaxy retains traces of spiral structure, but its star forming days are long gone.

I'm still mulling over the fact that M94 is only 30,000 light years across. That really makes it a quite small galaxy, half the size of M33, which looks smaller than M94 to me. Perhaps it is the chaotic structure of M33 that makes it look small to me.

Ann

[starsurfer]

In H-alpha, the most striking feature of M94 is a tight ring of H II regions just at the boundary where the surface brightness of spiral structure changes. Here is an old continuum-subtracted) image in pseudo color:

M94VCVHa2.jpg

(Historical "grumpy old astronomer" note - I'm pretty sure the existence of the outer ring (although not its detailed structure) was noted by Sandage in the Hubble Atlas, and there are literature references to it from the 1970s, but I can't double-check at the moment since my copy is at home).

Thanks for the extra information, I had a feeling there was more with Ha. It is likely it was already known in the past but maybe forgotten about and then rediscovered later.

[starsurfer]

This is a pretty cool galaxy! What's more interesting is that the outer ring has been known for less than 20 years and I think might have been discovered by the amateur astrophotographer R. Jay GaBany. If you look carefully, you can see some small star clusters, starclouds and nebulae in the outer ring as well as the central part. Has anyone ever taken a Ha image of this galaxy?

Great work by GaBany!

Interestingly, there are some similarities between M94 and M77, although M77 is a much larger galaxy with an active core. One of the similarities is that M77 also has widespread outer arms with star formation.

Ann

That's a great comparison, hadn't thought of that. M77 is also known to have Ha and OIII in its core region.