Great Attractor

We are obviously attracted to the Earth. The second obvious attraction is to the sun. The next attraction is a little bit more obscure because it is located 28,000 light-years away from us. The center of the Milky Way galaxy is a great center of gravitational attraction of most objects visible to the naked eye. The last "Great Attractor" known to us is a little more obscure. It lies 400,000,000 light-years away and seems to attract our entire local group (Andromeda, Milky Way, Triangulum Galaxy, M110, M32 etc…). There are however many things obscuring our view of it. The interstellar medium blocks 20% of our visible sky, and in this case the Great Attractor lies within that 20%. It is a conglomeration of perhaps 100,000 galaxies beyond the local group.

    It appears that the Earth is moving, in the direction of the constellation Leo (RA: 11.2h, dec: -7deg), around 380 km/s. This does however include the revolution of the Sun around the galaxy, and includes the movement of the Milky Way about the center of the local group. This taken into account sum to around 300 km/s in the direction of the constellation Cygnus. After correcting for this one finds the local group is moving at around 600 km/s relative to the cosmic microwave background, measured via Doppler-shift, in the direction of the Hydra-Centaurus supercluster.

The Great Attractor is far bigger than a galaxy. In the terminology of astronomers, there are clusters of galaxies containing maybe hundreds of galaxies, and superclusters containing many clusters. The Great Attractor is a supercluster or something even bigger.