The Great Attractor

 by  Shaun Lawton (roving reporter for the Oscillating Oculus). 

   "Does a pie sliced into 14 unequal pieces even feel the knife that sectioned it?  It's a trick question, since the Great Attractor balances out our whole life."  

   The Great Attractor is the apparent central gravitational point of the Laniakea Supercluster of galaxies which includes the Milky Way as well as about 100,000 other galaxies.  Lanieakea is part of the Pisces-Cetus Supercluster Complex, which itself can be described as a galaxy filament, the largest known structures in the universe.  These galactic filaments are massive, thread-like formations that function like dividing walls forming the boundaries between voids (also known as "dark spaces").   These dark spaces or voids contain very few if any galaxies, because the vast majority of galaxies remain gravitationally bound together forming galaxy filaments.   Most of these "void pockets" are between 10 and 100 megaparsecs in diameter (30 to 300 million light years) and even larger ones are referred to as supervoids.  

   The observed attraction (of the Great Attractor) suggests a localized concentration of mass on the order of ten-quadrillion solar masses. However, it is somewhat hidden from our view by the Milky Way's galactic plane, lying behind the Zone of Avoidance ("ZOA"). It turns out that the Great Attractor is difficult to observe directly in visible light wavelengths.  (The attraction itself is observable by its effect on the motion of galaxies and their associated clusters over a region of hundreds of millions of light-years across the universe). 

   To be clear, these galaxies are observable above and below the Zone of Avoidance; yet all of them are redshifted in accordance with the Hubble flow, indicating that they are receding relative to the Milky Way and to each other, but the variations in their redshifts are large enough and regular enough to reveal that they are slightly drawn towards the attraction. 

   These variations in their redshifts are known as "peculiar velocities", and cover a range from about +700 km/s to −700 km/s, depending on the angular deviation from the direction to the Great Attractor.

   What's interesting to know, is that the Great Attractor itself is moving towards the "Shapley Supercluster", and furthermore, recent astronomical studies by a team of South African astrophysicists have revealed that in the Great Attractor's theorized location lies a supercluster of galaxies known as the "Vela Supercluster."  

   The Shapley Supercluster appears as a striking overdensity in the distribution of galaxies in the constellation of Centaurus, itself located 650 million light years away from us.  It is the largest concentration of galaxies in our nearby universe that forms a gravitationally interacting unit (therefore appearing to be pulling itself together rather than expanding with the universe).  

   The Vela Supercluster is even farther away from us (at a distance of about 870 million light years) and is thought to be within the vicinity of the Zone of Avoidance, itself centered on the constellation Vela.    *

*to be  (or not to be) cont.