Friday, April 24, 2015

When black holes meet and "the big empty"


Time now again for Science Friday.

Two very interesting stories on space and astronomy caught my attention this week. Yes, believe it or not, even if it has nothing to do with UFOs, space still interests me. Photos of galaxies and nebulae from the Hubble put me into a place of complete sang-froid. But I digress...

First was this bit on research that suggests we're about to see what happens when two black holes pair and perhaps merge. This will be the first time that astronomers have ever witnessed such a thing. The leading belief at this time is that both black holes have synchronized and are producing a quasar that cycles between bright and dim. Quasars are once mysterious space objects that are extraordinarily bright and are thought to be expressions of energy that occur as matter falls into a black hole.

In the course of study of this quasar, astronomers found it followed a bright/dim pattern of every 542 days. The most likely explanation for this is that two galaxies are merging and that each galaxy has a black hole. These black holes are now in such near proximity that they are orbiting as a binary system.

Wow. This really is new. Granted I'm not an astronomer, but if someone had asked me just yesterday whether I thought this could happen with black holes, I would have issued a definite "no." Guess it's a good thing that I stuck with English.

Speaking of holes, astronomers have found a big one. In fact, it is now the largest known structure in the universe.

It's being called "the supervoid." It is a spherical blog 1.8 billion light years across...and it is really really empty. At least in astronomical terms, anyway. Turns out its not perfectly empty, but has 20% less material in it than other sections of the universe.

This "big empty" as I prefer to call it, was first suspected ten years ago when it was noticed in an astronomical study as being suspiciously cold. Stands to reason as such an empty expanse would have to be colder than even the frigidness of regular space. Turns out this a bit of hitch in the Big Bang model of the universe. As stated at the linked article:

"Cosmological theory allows for a bit of patchiness in the background temperature, due to warmer and cooler spots of various sizes emerging in the infant universe, but areas as large and cold as the Cold Spot are unexpected."

An article over at Discover puts it in analogous terms:

"To understand the effect of a void, imagine the universe is like a Swiss cheese, with holes – voids – corresponding to empty spaces devoid of matter and gravitational pull. When a photon, a particle of light, from the CMB [Cosmic Microwave Background] encounters a void it will lose energy but regain it as it exits.

However, since we believe that the universe is constantly expanding, the photon will exit into a medium that is less dense than before it entered the void. Lower density means weaker gravitational pull on the emerging photon. This means that the photon cannot make up all the energy it lost and ends up with a little less energy – and hence lower temperature – than light from regions on the sky that did not pass through the void."

So 1.8 billion light years of the cosmological equivalent of nothing? Suddenly I don't feel so bad about myself.





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