APOD: NGC 5078 and Friends (2016 May 25)

[APOD Robot]

NGC 5078 and Friends

Explanation: This sharp telescopic field of view holds two bright galaxies. Barred spiral NGC 5101 (top right) and nearly edge-on system NGC 5078 are separated on the sky by about 0.5 degrees or about the apparent width of a full moon. Found within the boundaries of the serpentine constellation Hydra, both are estimated to be around 90 million light-years away and similar in size to our own large Milky Way galaxy. In fact, if they both lie at the same distance their projected separation would be only 800,000 light-years or so. That's easily less than half the distance between the Milky Way and the Andromeda Galaxy. NGC 5078 is interacting with a smaller companion galaxy, cataloged as IC 879, seen just left of the larger galaxy's bright core. Even more distant background galaxies are scattered around the colorful field. Some are even visible right through the face-on disk of NGC 5101. But the prominent spiky stars are in the foreground, well within our own Milky Way.

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[Jim Leff]

First link is dead, fwiw.

[Ann]

Beautiful image.

Since APOD Robot had helpfully informed us that NGC 5078 would be in today's picture, I had already checked out some facts about it and decided to compare it with M104, the Sombrero galaxy.

Click to view full size image

M104. Photo: NASA/ESA and The Hubble Heritage Team (STScI/AURA)

NGC 5078 and M104 are, to a degree, similar in type. Both are edge-on spiral galaxies of Hubble type Sa, with large bulges and tightly wound spiral arms. But they are very different, too. Fascinatingly, the Sombrero is both redder and bluer than NGC 5078. It is bluer in that its B-V index is bluer than that of NGC 5078, 0.980 versus 1.040, but it is redder in that its U-B index is redder than that of NGC 5078, 0.530 versus 0.360. And M 104 is much fainter than NGC 5078 in far infrared light. Even though M104 is about three magnitudes brighter in visual light in our skies than NGC 5078, the latter is more than half a magnitude brighter than M104 is far infrared light even at its farther distance from us.

Conclusion? M104 is a staid, settled galaxy, with a well-ordered dust lane where nothing much is happening. NGC 5078 is a smaller galaxy, far less well-behaved and much dustier, which reddens the visual light from this galaxy. But there is star formation going on in NGC 5078, which by all accounts is missing in M104.

In today's APOD, we can actually see the pink nebulas characteristic of star formation in the outer arms of NGC 5101, the large face-on galaxy. And I think we can see hints of star formation in the upper parts of the dust lane in NGC 5078.

Fascinating image! Thanks!

Ann

[mjsakers]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

[starsurfer]

This is an astonishingly deep image of an awesome galaxy field in Hydra! I think this is the first image where I have seen a few emission nebulae in the mostly featureless spiral arms of NGC 5101. It would be cool to see a closeup taken by the CHART32 team!

[starsurfer]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

I'm not much of a galaxy guy to answer your question but I'm pretty positive you will receive a reply from someone called Chris Peterson.

[heehaw]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

I'm not much of a galaxy guy to answer your question but I'm pretty positive you will receive a reply from someone called Chris Peterson.

This is an urgent question, because ... because ... well, maybe it isn't so urgent, what difference does it make?

[neufer]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

The obvious distortions of both NGC 5078 & IC 879 can only be explained by an interaction:

<<NGC 5078 is a spiral galaxy in the Hydra constellation, approximately 94 million light-years away from Earth. It has a diameter of 127,000 light-years and is probably a member of the NGC 5061 group. The dust lane of NGC 5078 is warped, probably by interaction with the nearby galaxy IC 879, which is itself distorted into an 'S' shape by the interaction. At the presumed distance the two galaxies would have a minimal separation of about 61,000 light-years. For comparison, the Large Magellanic Cloud is about 160,000 light-years from the Milky Way.>>

[Chris Peterson]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

I'm not much of a galaxy guy to answer your question but I'm pretty positive you will receive a reply from someone called Chris Peterson. :D :lol2:

Or Art.

[Fred the Cat]

The statement in the "In fact" link "It is very rare however for a galaxy to be completely isolated in space" made me think of the Maytag repairman ad line. Curious I was looking for an example of a lonely galaxy. What other things do bored but curious people think of during their periods of contemplation? Maybe why are they so far off the beaten track?

[bystander]

First link is dead, fwiw.

It seems the AAO is constructing a new image gallery. Links to the images at the old gallery are available, NGC 5101 and NGC 5078.

[Ann]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

These two galaxies, NGC 5078 and IC 879 (the small spiral galaxy) display very similar recession velocities (around 2000 km/second). In other words, they seem to move away from us at basically the same speed. They are also very close to one another in the sky. In addition, we can see signs of disturbance in the galaxies. NGC 5101 has a distorted dust lane, and IC 879 has spiral arms of unequal lengths, where the longest one is closer to NGC 5101. Such disturbances are to be expected if the galaxies are exerting gravitational forces on one another.

Taken together, these facts strongly suggest that the galaxies are at the same distance from us and are interacting with one another.

Ann

[Coil_Smoke]

Barred spiral NGC 5101 shows vast purple regions. I'm used to seeing star forming area in pink. The expanded view of NGC 5078 is full of beautiful purple and looking very energetic. Are we seeing a representation of actual color ? Is the purple caused by X-ray emission ?

[Ann]

Barred spiral NGC 5101 shows vast purple regions. I'm used to seeing star forming area in pink. The expanded view of NGC 5078 is full of beautiful purple and looking very energetic. Are we seeing a representation of actual color ? Is the purple caused by X-ray emission ?

No, the purple areas certainly represent regions of star formation.

The purple hue is a result of filters, exposures and post processing.

Interestingly, there are hints of reddish-pink nebulas in NGC 5078 too, and they don't look purple at all. It is as if the two galaxies have been processed in different ways. Alternatively, the nebulas in NGC 5078 are so reddened by dust that all their blue light has been filtered away.

But above all, we can be sure that the purple areas in NGC 5101 are regions of star formation because of their distribution. They follow the spiral arms. This is typical of galaxies of type Sa, which have large bulges and elegant, regular spiral arms. Compare NGC 5101 with M81.

Click to view full size image

X-ray sources in M81 (blue).
Image: X-ray: NASA/CXC/Wisconsin/D.Pooley & CfA/A.Zezas; Optical: NASA/ESA/CfA/A.Zezas;
UV: NASA/JPL-Caltech/CfA/J.Huchra et al.; IR: NASA/JPL-Caltech/CfA

But check out this composite image of M81, where X-ray sources are blue. They are scattered all over the place, and most of them don't follow the spiral arms at all.

Ann

[j_star]

Hi Guys,

I think APOD is fantastic. I'm in awe of the images and enjoy reading the explanations.

I happened to notice that a very similar image appeared as an APOD on February 8 2014 (http://apod.nasa.gov/apod/ap140208.html). Today's image looks like a reflected image of the 2014 image but it is not as simple as this: It looks like the galaxies have moved in relation to each other, in two years! Can anyone explain what's going on?

i'd be interested in anyones views.

[geckzilla]

Hi Guys,

I think APOD is fantastic. I'm in awe of the images and enjoy reading the explanations.

I happened to notice that a very similar image appeared as an APOD on February 8 2014 (http://apod.nasa.gov/apod/ap140208.html). Today's image looks like a reflected image of the 2014 image but it is not as simple as this: It looks like the galaxies have moved in relation to each other, in two years! Can anyone explain what's going on?

i'd be interested in anyones views.

Heh, that's pretty funny. Pugh's is mirrored horizontally and rotated from the real sky. Benson's is just rotated.

[DavidLeodis]

First link is dead, fwiw.

It seems the AAO is constructing a new image gallery. Links to the images at the old gallery are available, NGC 5101 and NGC 5078.

Thanks for those links bystander . It came as quite a surprise when I clicked on the links to those 2 in the explanation to get a message for both in which it stated "In the period preceding an election for the House of Representatives, the Australian Government assumes a caretaker role (see the Guidance on Caretaker Conventions from the Department of Prime Minister and Cabinet). As this website is hosted by the Australian Astronomical Observatory (a division of the Department of Industry, Innovation & Science), content will be moderated from the time the House of Representatives is dissolved until after the election to ensure that political material is not placed on the site".

[starsurfer]

How do we know for sure that NGC 5078 is interacting with IC 879? IC 879 sure looks much further in the distance, and there's no real visual evidence of interaction (don't say it's the S-shape of IC, that doesn't prove anything). It's smaller apparent size is explained by saying it's a dwarf galaxy, but I just want to know why it isn't just as likely that it is a more distant galaxy that just happens to line up close to NGC 5078?

I'm not much of a galaxy guy to answer your question but I'm pretty positive you will receive a reply from someone called Chris Peterson.

Or Art.

Looks like I'm going to have to give up my role of soothsayer.

[Ann]

I'm not much of a galaxy guy to answer your question but I'm pretty positive you will receive a reply from someone called Chris Peterson.

Or Art.

Looks like I'm going to have to give up my role of soothsayer.

Hey, I thought I was the galaxy guy... gal... here at this site!

(Unless Geck's the one... I guess she has seen more galaxies than anyone else at this forum.)

Ann

[geckzilla]

I dunno. Some people like to memorize NGC galaxies. I don't. I think we're all a bunch of know-it-alls who use Internet search engines to find stuff.