The great attractor.

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The great attractor.

In: Physics
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Let’s zoom out, the Earth and our Planets orbit the Sun. The Sun and the other stars in our Galaxy orbit what is likely a black hole at the center of the Milky Way. The Milky Way Galaxy then fits into a cluster of other Galaxies called the Virgo Cluster. The Virgo Cluster of galaxies fits in with other clusters called the Virgo Supercluster. The Virgo Supercluster fits with other Superclusters into what we call the Local Group. The Local Group is a part of the Laniakea supercluster.

So you can at least imagine that Laniakea is large beyond any comprehension.

Just like Earth orbits the sun, it’s believed that Laniakea has some sort of super-massive gravitational center that it’s constituent superclusters are attracted to. Astromers can’t actually *see* what this attractor is but they can infer it’s presence by how it tugs and pulls around Laniakea. The reason why astronomer’s can’t see the Great Attractor directly is because it’s located directly through the center on the far side of the Milky Way.

TL/DR: Its just a normal cluster of galaxies, there’s nothing *actually* mysterious about it but we couldn’t see it until 1999 so it became a sort of astronomy pop culture mystery.

Until 1999 it was only possible for humanity to observe the universe by looking at visible light and certain very long wave length radio waves.

Visible light can’t penetrate dust, Since the center of the Milky Way is filled with dust we can’t see anything on the other side of the galaxy.

Very long wave length radio waves have a very, very low resolution. Think of the difference between visible light and VLWL radio waves as being like the difference between taking a picture on a 100 megapixel phone and a 1 pixel phone. With the 100 megapixel phone you can see a lot of detail. With the 1 pixel phone all you can see is a single dot of white or black. So we could technically image the Great Attractor with VLWL radio waves, but all that told us was that, yes, there was matter in the direction of the Great Attractor.

While we couldn’t see the Great Attractor in any meaningful detail, we could see all of the Galaxies that are above and below ours, and from viewing those it became apparent that everything nearby was moving in the direction of the mysterious object that we couldn’t see.

In 1999 NASA launched the Chandra X-ray Telescope into outer space. X-rays can penetrate the dust at the center of the galaxy *and* produce a much higher quality picture than visible light. With the Chandra Telescope we were able to take pictures of the Great Attractor, which is actually just a galaxy cluster called the Norma Cluster.

There is nothing particularly special about the Norma Cluster. Similar galaxy clusters exist all over the universe. Also, as it turns out, the Norma Cluster is just sitting in front of the Shapely Supercluster, which is an even larger galaxy cluster, and its actually the Shapely Supercluster that we’re moving towards.