How Big Are Galaxies?

I’m going to refrain from the initial response that comes to mind… actually, no I won’t — they’re really, really, really big!!!!

</Kermit arms>

Ok, now that that’s out of the way check out this graphic by Arecibo astrophysicist Rhys Taylor, which neatly illustrates the relative sizes of 25 selected galaxies using images made from NASA and ESA observation missions… including a rendering of our own surprisingly mundane Milky Way at the center for comparison. (Warning: this chart may adversely affect any feelings of bigness you may have once held dear.) According to Taylor on his personal blog, Physicists of the Caribbean (because he works had worked at the Arecibo Observatory in Puerto Rico) “Type in ‘asteroid sizes’ into Google and you’ll quickly find a bunch of  images comparing various asteroids, putting them all next to each at the same scale. The same goes for planets and stars. Yet the results for galaxies are useless. Not only do you not get any size comparisons, but scroll down even just a page and you get images of smartphones, for crying out loud.” So to remedy that marked dearth of galactic comparisons, Taylor made his own. Which, if you share my personal aesthetics, you’ll agree is quite nicely done.

“I tried to get a nice selection of well-known, interesting objects,” Taylor explains. “I was also a little limited in that I needed high-resolution images which completely mapped the full extent of each object… still, I think the final selection has a decent mix, and I reckon it was a productive use of a Saturday.” And even with the dramatic comparisons above, Taylor wasn’t able to accurately portray to scale one of the biggest — if not the biggest — galaxies in the observable universe: IC 1101.

For an idea of how we measure up to that behemoth, he made this graphic:

Galaxy sizes including IC 1101, the largest-known galaxy. Click for a zoomable version. (Credit: Rhys Taylor)
Galaxy sizes including IC 1101, the largest-known galaxy. Click for a zoomable version. (Credit: Rhys Taylor)

That big bright blur in the center? That’s IC 1101, the largest known galaxy — in this instance created by scaling up an image of M87, another supersized elliptical galaxy that just happens to be considerably closer to our own (and thus has had clearer images taken of it.) But the size is right — IC 1101 is gargantuan.

At an estimated 5.5 million light-years wide, over 50 Milky Ways could fit across it! And considering it takes our Solar System about 225 million years to complete a single revolution around the Milky Way… well… yeah. Galaxies are big. Really, really, reallyreally big!

</Kermit arms>

Now if you’ll pardon me, I need to go stop my head from spinning… Read this and more on Rhys Taylor’s blog here, and add Rhys to your awesome astronomy Google+ circles here. And you can find out more about IC 1101 in the video below from Tony Darnell, aka DeepAstronomy:

22 Replies to “How Big Are Galaxies?”

  1. “IC 1101 will slowly fade into oblivion”

    That depresses me really bad, for some reason.

  2. this is absolutely astounding, 50 milky ways can fit into IC1101,this has to be crazy, Where is this all happening, is there more than 1 Universe – like cud the number of Universes b the similar as the number of galaxy’s ? Could this be unreal ?

  3. Good! Higher resolution images of the two frames? I dragged them to my desktop hoping to see details by zooming, but names became blurs due to low resolution.

  4. My theory is the Milky Way probably has an undiscovered fainter disk or radio jets that makes it much bigger than it is portrayed in this illustration.

    1. My thought also. In the first image Andromeda looks a little smaller than Milky Way, yet the fainter disk makes it bigger.

  5. Hi, thanks for highlighting this nice piece of infographic.

    In the words of Columbo, ‘just one more thing’.

    “At an estimated 5.5 billion light-years wide, over 50 Milky Ways could fit across it!”. Should that read 5.5 million light-years wide? If it was 5.5 billion light-years wide, we’d be inside it! haha

    1. Yes, million, not billion. English not only makes the two words similar, but also places their first letters annoyingly close on the keyboard. Fixed.

  6. IC 1101 – “At an estimated 5.5 billion light-years wide” would span almost 1/3 of the known observable universe in depth, and would pack 50,000 Milky Way galaxies across.

  7. I’m tired of seeing artists conceptions of our galaxy. I have a list of people I’d be happy to strap to a thruster to be sent out of the galaxy to make some sketches.

  8. The zoomable image got me thinking. Given the Milky Way’s size on this image, would our solar system or the plaent earth be close to the size of a hydrogen atom? If not, what object would be a good size comparitor for the Earth/solar system and the size of the milky way shown in this image?

  9. Bigger pictures, please! The more useless pictures you post, where I can’t even read the text, the more I go to other websites for my astro-news. Phil Plait does a great job with pictures that I can galactinate, make my desktop and even read labels on. Thanx!

  10. I thought about it, but it’s much too small to be visible. Maybe in a subsequent dwarf galaxies version.

    1. A comparison chart for dwarf galaxies would make a great addition to your (excellent) galaxy size comparison. This would cover the low mass end of the galaxy spectrum and, after all, most galaxies in the universe are of the dwarf variety.

      1. Fantastic! The addition of Hanny’s Voorwerp and Minkowski’s Object is a nice touch. I’m planning on making poster-size versions of these graphics for my office. Many thanks for putting together these informative charts.

  11. This is
    correct comparison, but there is necessary to take into account the thickening
    of the space according to USM If we take into account the
    distance to the examined galaxy and the angular velocity of rotation of this
    galaxy, then we can find out what is the truly size of the galaxy!

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