Home Sweet Blasted Clean Void

The Local Cavity

What you’re looking at there is something called The Local Cavity–although in this case “local” takes on a meaning somewhat larger than in typical conversation. It’s essentially a 300-light-year in diameter hole in space. Maybe ‘hole’ is stretching it a bit, since it’s not so much that it’s empty, as that it’s WAY less full than the average across the galaxy.

These findings, and the 3D maps that come with them come from research done by a team at University of California, Berkeley. Their full paper (from which the image is taken) is freely available online if you want to see more about how they came to their findings, or see some of the other visuals generated from their map.

For a more popularized version of the really cool bit, let me quote the Discover.com article:

What is obvious in the maps is a white region in the center (where the sun is located), highlighting the Local Cavity. On the edges of the cavity is a “wall” of very dense, neutral gas interspersed with “interstellar tunnels.” These tunnels connect our cavity with other surrounding cavities.

Interestingly, by analyzing one particular absorption line (caused by doubly ionized calcium — CaII), it appears that the Local Cavity contains filamentary structures of partially ionized gas, creating a honeycomb-like pattern of smaller interstellar cells.

Although the cause of this cell-like structuring is unknown at present, it is thought that the Local Cavity was formed after a series of supernovae detonated nearby, blowing the cool, dense interstellar medium away and replacing it with a very tenuous volume of hot plasma, creating a ‘bubble.’

The idea that we live in the blast hollow of a series of supernovae is cool enough on its own, but for someone who’s done the sensawunda reading I’ve done, everything up there connects to all kinds of fantastical SF ideas.

The fact that we are in a pocket? The fact that there’s a dense wall around this pocket? The fact that even the Cavity itself is made up of a honeycomb of cells left from popping bubbles of post-supernova plasma? Every one of those things resonates with stuff I’ve been reading for years. The echos of science fiction just makes the awesome chorus of science sound even cooler.

  2 comments for “Home Sweet Blasted Clean Void

  1. Lachlan O'Dea
    March 14, 2010 at 7:04 pm

    The amount of interesting stuff we find going on in what initially appears to be “empty” space freaks me out.

  2. March 16, 2010 at 1:10 am

    Yeah, I know what you mean.

    Of course, there’s rather a lot of it–I mean for astronomers it’s “local” but think about the size of it–a sphere with a 150-light-year radius has what volume?

    That’s 4/3 * pi * (1.41907926 × 1015km)3, right? What’s that, around 6 X 1045 cubic km?

    With that much space, it can be pretty damn low average density and you’ll still find a lot of stuff in the ball, you know?

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Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Canada
This work by Chris McLaren is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Canada.