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Interacting galaxies

Interacting galaxies
Click for original image.

Cool image time! The picture to the right, reduced and sharpened to post here, was taken by the Hubble Space Telescope as part of a dark energy survey. It shows two galaxies very close together, their perpheries only about 40,000 light years apart, with the larger galaxy about the size of the Milky Way.

For comparison, the Large Magellanic Cloud (LMC) is about 167,000 light years from the Milky Way, more than four times farther that this satellite galaxy. Yet the satellite galaxy here appears much larger than the LMC, having a central core that the LMC lacks. From the caption:

Given this, coupled with the fact that NGC 5996 is roughly comparable in size to the Milky Way, it is not surprising that NGC 5996 and NGC 5994 — apparently separated by only 40 thousand light-years or so — are interacting with one another. In fact, the interaction might be what has caused the spiral shape of NGC 5996 to distort and apparently be drawn in the direction of NGC 5994. It also prompted the formation of the very long and faint tail of stars and gas curving away from NGC 5996, up to the top right of the image. This ‘tidal tail’ is a common phenomenon that appears when galaxies get in close together, as can be seen in several Hubble images.

In this single picture we are witnessing evidence of a process that has been going on for likely many millions of years.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

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  • Barry

    It would be interesting to know what the depth in light years there is between these two galaxies. Maybe there is a supercomputer that can calculate that relative to the motion in the stars in the two galaxies. I just find it difficult to believe that two “buzzsaws” met in the exact same eccliptical plane.

  • The killer app for 3D goggles is stuff such as this that requires 3D to understand. Vector arrows wouldn’t hurt, either.

    Presumably, the little one came in from the right somewhere, judging from the stretched spiral arm, but above or below? And where is that tidal tail? Was it “blown off” perpendicular to the “collision”. Perpendicular to which axis? A bow wave? A wake?

    I think it was here that I saw a time-lapse picture of something far away that we’ve been observing for decades (some nebula perhaps?) and stuff moved about 5 pixels, but it was 10s of light years. The app needs zoom, fast forward, and rewind features.

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