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Twin Spiral Galaxies Dance Together


This incredible image looks like space art, or a trick done with Photoshop, but its an actual image of twin galaxies dancing together in the sky. The image was obtained, appropriately enough by the Gemini South telescope in Chile using GMOS, the Gemini Multi-Object Spectrograph. These two nearly identical spiral galaxies are in Virgo, 90 million light years distant, in the early stages of a gentle gravitational embrace.

Like two dancers grabbing hands while passing, NGC 5427 (the nearly open-faced spiral galaxy at lower left) and its southern twin NGC 5426 (the more oblique galaxy at upper right), are in the throes of a slow but disturbing interaction – one that could take a hundred million years to complete.

At a glance, these twin galaxies — which have similar masses, structures, and shapes and are together known as Arp 271 – appear undisturbed. But recent studies have shown that the mutual pull of gravity has already begun to alter and distort their visible features.

Typically, the first sign of a galaxy interaction is the formation of a bridge-like feature. Indeed, the two spiral arms on the western (upper) side of NGC 5426 appear as long appendages that connect with NGC 5427. This intergalactic bridge acts like a feeding tube, allowing the twins to share gas and dust with one other across the 60,000 light years (less than one galaxy diameter) of space separating them.

Colliding gases caused by the interaction may have also triggered bursts of star formation (starbursts) in each galaxy. Star-forming, or HII, regions appear as hot pink knots that trace out the spiral patterns in each galaxy. HII regions are common to many spiral systems, but the giant ones in NGC 5426 are curiously knotted and more abundant on the side of the galaxy closest to NGC 5427. Starburst activity can also be seen in the galaxy’s connecting bridge.

Once thought to be unusual and rare, gravitational interactions between galaxies are now known to be quite common (especially in densely populated galaxy clusters) and are considered to play an important role in galaxy evolution. Most galaxies have probably had at least one major, if not many minor, interactions with other galaxies since the advent of the Big Bang some 13 billion years ago. Our own Milky Way, a spiral galaxy like those in this image, is, in fact, performing its own stately dance. Both with the nearby dwarf galaxy, called the Large Magellanic Cloud and a future interaction with the large spiral galaxy M-31 or the Great Andromeda Galaxy, which is now located about 2.6 million light years away from the Milky Way. This new Gemini image is possibly a preview of things to come for our own galaxy. Ultimately the end result of these types of collisions will be a large elliptical galaxy.

Original news source: Gemini Observatory

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • Amir June 26, 2008, 9:13 AM

    That’s unbelievable. That means that this picture is how these 2 galaxies were 90 million years ago, but at this moment in time they are probably merged or something, but we won’t know for another 90 million years!!!

    So incredible the distances in space.

  • zifferman June 26, 2008, 9:14 AM

    Clearly these two galaxies are getting it on.

    Maybe we should let them have their privacy, people? Geesh!

    After all, we can’t just tell them why don’t they
    get a room. A universe maybe, but….

  • Sakib June 26, 2008, 11:05 AM

    Awww thats sweet, two galaxies in love! It’s last for millions of years!

  • Nexus June 26, 2008, 3:00 PM

    Look at the band of stars connecting the two galaxies. On a planet orbiting one of those stars, the night sky must be absolutely spectacular.

  • Steve June 26, 2008, 3:03 PM

    It’s a glimpse to our future when the Andromeda galaxy plows into us (or us them)

  • Astrofiend June 26, 2008, 4:14 PM

    “# Nexus Says:
    June 26th, 2008 at 3:00 pm

    “Look at the band of stars connecting the two galaxies. On a planet orbiting one of those stars, the night sky must be absolutely spectacular.”

    I love speculating about that sort of thing. Spectacular indeed!

  • marcellus June 27, 2008, 12:31 AM

    South up is typical for a Newtonian reflector, but I doubt that is what Gemini south is configured at.

    At any rate, it is an awesome picture of two interacting galaxies.

    What is the minimum aperture that an amateur astronomer observe these two with?

  • dilip June 26, 2008, 11:31 PM

    It’s a strange way to show a picture, with south up!

  • ron stone June 27, 2008, 9:18 AM

    Afraid your right about that. We too should have a fantastic view of the galactic centre but for the gasses and dust in the way. But think how lucky we are to live in an age when we can look at these sort of images. I always check this sight out first in the morning and am constantly astounded at the images that are almost becoming commmon place!

  • AJames June 27, 2008, 3:34 AM

    Thanks for this interesting article.

    IMPORTANT COMMENT :

    I would like to point out just a minor flaw which seems endemic of the articles that appear in Universe Today (and elsewhere),

    If you must discuss an object, PLEASE give both the constellation that it is in and the co-ordinates of the object(s) in question.

    Those wishing to seek out more information on the Net or even planetarium software about the objects can then at least make some general assessment about the article and its implications (without much though interpreting the image). Ie. As the galaxies are in the “constellation of” Virgo – and thus they imply both are reasonably close galaxies to us. (At least Nancy has done this, but this is not always the case!)

    However, the Right Ascension and Declination positions are not, meaning you have to go somewhere else find where they are.
    I.e. Try Goggling “NGC 5427″, and you will find it as the 19th on the list (assuming you have set the preferences to be twenty items instead of the default of ten. Type “NGC 5426″ )

    Note: The RA and Dec of NGC 5427 is 14h 03.4m -06 deg 02′ and NGC 5426 is 14h 03.4m -06 deg 04′

    Note 2: Readers can quick;y find details on these galaxies in the “NASA/IPAC Extragalactic Database (NED)

    Note 3: The current distance of 90 million light-years seems to small. Using the value of 38.9 Mpc (mega parsecs – million parsecs) gives 126.9 M.ly for NGC 5426 AND 39.6 Mpc or 129.2 M.ly. This makes the mean distance more like 127.8 or 128 million light years.

  • AJames June 27, 2008, 3:37 AM

    Sorry

    The distances in the last paragraph should be;

    NGC 5426 : 38.9 Mpc or 126.9 M.ly for NGC 5426
    NGC 5427 : 39.6 Mpc or 129.2 M.ly.

    Mean distance of both are more like;
    127.8 or 128 million light years.

    Andrew

  • Greg June 27, 2008, 5:07 AM

    This configuration of two galaxys colliding seems like an ideal test subject to find evidence of dark matter and its distribution

  • neoguru June 27, 2008, 7:37 AM

    Would the view from a planet circling a star between the galaxies really be that spectacular? I suspect the gas and dust would obscure most of the sight just as it does within our own galaxy. Pity.

  • robbb June 27, 2008, 9:49 AM

    we do have an amazing view right here, right now. especially considering at some point in the very very distant future there will be no stars in the night sky at all once the galaxies have drifted far enough apart.

  • Nexus June 27, 2008, 4:25 PM

    Neoguru:
    I’m pretty sure most of the dust and gas in a galaxy is contained within the galactic disc. The reason we can’t see our galactic core is that we’re right in the plane of the galactic disc ourselves and so we’ve got all those dust clouds right in our line of sight.

    We can see the cores of those twin galaxies because we’re looking at them pretty much from directly above. As long as the band of stars I was talking about isn’t directly in line with either galaxy’s disc, an observer there should have a great view of both galactic cores.

  • Brack the barbarian June 28, 2008, 12:46 PM

    Fabulous picture but what is the mysterious object to the right of the centre of the face on galaxy and below the centre of the oblique one (at roughly the apex of where an imaginary triangle would be)? It’s a small bilobate blob which seems to be extruding a fainter blob from its middle. It’s presumably a more distant galaxy, I certainly can’t think what else it might be, but what is going on???

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