The Two Shall Become One (Galaxy, that is)

Article written: 16 Mar , 2009
Updated: 24 Dec , 2015
by

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An imminent collision of biblical proportions has been captured by the Hubble and Spitzer Space Telescopes. The image here offers a rare view of a collision about to happen between the cores of two merging galaxies, each powered by a black hole with millions of times the mass of the sun. Already this union is considered to be one galaxy: NGC 6240, located 400-million light years away in the constellation Ophiuchus. Millions of years ago, each core was the dense center of its own galaxy before the two galaxies collided and ripped each other apart. Now, these cores are approaching each other at tremendous speeds and preparing for the final cataclysmic collision. They will crash into each other in a just a few million years.

“One of the most exciting things about the image is that this object is unique,” said Stephanie Bush of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., lead author of a new paper describing the observation in an upcoming issue of the Astrophysical Journal. “Merging is a quick process, especially when you get to the train wreck that is happening. There just aren’t many galactic mergers at this stage in the nearby universe.”

Download and extra-large version of this image here.

It combines visible light from NASA’s Hubble Space Telescope and infrared light from Spitzer. It catches the two galaxies during a rare, short-lived phase of their evolution, when both cores of the interacting galaxies are still visible but closing in on each other fast.

NGC 6240 is already putting out huge amounts of infrared light, an indication that a burst of star formation is underway. The extra infrared radiation is common in interacting galaxies; as the two galaxies interact, dust and gas swept up by the collision form a burst of new stars that give off infrared light. Such galaxies are called luminous infrared galaxies. Spitzer’s infrared array camera can image the extra heat from newly formed stars, even though their visible light is obscured by thick dust clouds around them.

The blob-like shape of the galaxy is due to the sustained violence of the collision. Streams of millions of stars are being ripped off the galaxy, forming wispy “tidal tails” that lead off NGC 6240 in several directions. But things are about to get even more violent as the main event approaches and the two galactic cores meld into one.

In the center of NGC 6240, the two black holes in the cores will whip up a frenzy of radiation as they careen towards one another head-on, likely transforming the galaxy into a monster known as an ultra-luminous infrared galaxy, thousands of times as bright in infrared as our Milky Way.

Another fascinating aspect of this rare object is that no two galactic mergers are the same. “Not only are there few objects at this stage, but each object is unique because it came from different progenitor galaxies,” said Bush. “These observations give us another layer of information about this galaxy, and galactic mergers in general.”

Infrared light taken by Spitzer’s infrared array camera at 3.6 and 8.8 microns (red) shows cold dust and radiation from star formation; visible light from Hubble (green and blue) shows hot gas and stars.

Source: JPL


16 Responses

  1. Very interesting article. The photo has some additional interest. Download the high resolution version and scroll over it. There are dozens of presumably more distant galaixies all around it.

  2. Jon Hanford says

    Notice also in the hi-res versions of this image the numerous bluish ‘star-like’ objects in the inner regions of the galaxy. These represent relatively young star clusters formed as a result of this cosmic collision. What a delicate, chaotic looking galaxy. Also cool, the numerous background galaxies, some also undergoing gravitational encounters.

  3. RBH says

    “An imminent collision of biblical proportions …”.

    Nope. Biblical catastrophes are very small potatoes compared to this.

  4. Mr. Greenjeans says

    Biblical proportions? Surely your word choice was not accidental. Now why would you do a thing like that?

  5. wandering by says

    Why? To make a joke or rather wordplay with the title.

    “Biblical proportions” is an oft used metaphor to indicate that an event, usually a disaster, will be/was of epic scale and as such suits this event nicely. I’m sure any residents of either galaxy would agree to the intent of the metaphor at least.

    Sensitive much? OMG! There, I did it again!

  6. Procyon says

    **The image here offers a rare view of a collision about to happen…**

    **They will crash into each other in a just a few million years.**

    Did’nt this already happen about 390 million years ago?

  7. fred houpt says

    I see something different. Consider that mainstream theory posits that older galaxies have passed through the robust star creation phase and one wonders then why no one is asking why this merging of old galaxies is creating new stars with such abundance? I would consider that what we are watching is not two mashing together into one, but the opposite: that one very old galaxy is now splitting into several new ones, thus creating babies along the way. Arp hangs over my shoulder…..we need new eyes…..and new knowledge….

  8. One Angry Scientist Among 12 Angry Scientist says

    Where’s the perchlorate connection?

  9. formulaterp says

    fred houpt Says:

    “that one very old galaxy is now splitting into several new ones, thus creating babies along the way”

    So galaxies are formed through mitosis? That might be the dumbest thing I’ve ever heard. No wait, I forgot about the Giant Lightning Bolts from Space.

  10. ND says

    According to galaxy collision simulations, galaxies pass through each other during a collision (they’re not solid objects like two cars :). So you should examples of galaxies hurtling towards each other and other examples of messed up galaxies speeding away (after they’ve passed through each other).

  11. brudrlove says

    How can we ascertain the speed of this collision?

  12. Themondo says

    If you look closely at the picture it looks like an angel with wings and a long flowing dress

  13. Olaf says

    And the funny thing is, when a galaxy collide’s and you happen to be inside such a colliding galaxy, you will probably not realize it.

  14. Biblical Proportions? Somebody says that means small because things in the Bible are small. Hey wake up everybody. The Big Bang is the largest event we know anything about. Much bigger than any pair of coliding galaxies (or splitting galaxy). And though you will chastize me for saying it, just remember some of us think the big bang began with the words “Let There Be Light”. And that is Biblical. And this event is so imminent. Just a few billion years. I can’t wait.

    Ray Bingham (with my tongue part way in my cheek).

  15. Bravehart says

    Maybe someone could tell me what the approximate distance is from the large star
    in front of this ” merger”? There is no info
    of the distance to our own world? I have my doubt that this”merger” is really taking place
    It maybe the line of sight that gives the impression? If this artical is real, it does not hold water to say the cores will merge in
    a few 1000 light years and move at tremendes speed? This implies that the cores are 1000 light years apart at present?
    It is a nice picture, but I do question if the
    observation and conclusion is correct?
    I have the utmost respect for Mr. Frazer Cain
    and hope that he can verify this artical?

  16. Excalibur says

    “Maybe someone could tell me what the approximate distance is from the large star
    in front of this ” merger”? There is no info
    of the distance to our own world? ”

    It says in the article the galaxies are about 400 million lightyears away. The star is obviously within our own galaxy, so probably a few 100 to a few 1000 of lightyears away from us.

    “I have my doubt that this”merger” is really taking place
    It maybe the line of sight that gives the impression? If this artical is real, it does not hold water to say the cores will merge in
    a few 1000 light years and move at tremendes speed? This implies that the cores are 1000 light years apart at present?”

    You lost me here, the article doesnt say the distance between the 2 cores, but it does mention they will crash into eachother in a few million of years, not 1000s of years. The cores may very well be a few 1000 lightyears apart, but as they are not moving at anything near lightspeed it will take much longer than that for them to meet eahother.

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