Home » Science & Nature » Astronomy » OUR black hole. Part II

OUR black hole. Part II

© Rodolfo Astrada

In the previous article we explored the anatomy of black holes, how you can build one, and what strange phenomena takes place in their immediate surroundings.

This time, we are going to deal with how they originated in the Universe, and how they behave, in particular the Milky Way supermassive beast located in the direction of Sagittarius. Its presence betrayed long ago by peculiar radio emissions from a point source by the name Sagittarius A* (colloquially pronounced A-star). To be fair, Sgr. A* is not the only black hole around here. There is sound theoretical foundation, and convincing observational evidence, for the existence of probably millions of smaller ones, those that are what's left after the demise of giant, short lived stars or neutron star mergers, matters which we promise to talk about in the near future.

In the beginning

Primordial matter in the early universe was not distributed evenly. It consisted mostly of hydrogen, a little bit of helium, and copious amounts of an as yet unidentified form of matter generically known as "dark matter". All other elements were synthesized from hydrogen and helium inside the nuclear furnaces of earlier stars. Dust of which we are all made, comes from probably 2 or 3 supernova blasts in successive generations of giant stars, the ones which live short, seed surroundings with fresh new material, and leave behind neutron stars or small black holes. Primordial unprocessed hydrogen though, is still by far the most abundant element in the Universe.

We learned matter (normal and dark) was not distributed uniformly, by scrutiny of echoes from the Big Bang. The analysis of this echoes (yet another future story) has been refined for the last 10 - 15 years, culminating with early results from the Wilkinson Anisotropy Probe spacecraft. It happens all too frequently with a major new experiment to yield unexpected results that send theoreticians scrambling back to their equations trying to figure out what they messed up with. Remarkably though, this time the biggest news was there was no news. The distribution and size range of primordial matter clumpiness - as inferred from background microwave radiation analysis - did fit nicely with standard cosmological models.

Being uneven in the first place, and being subject as usual to mutual gravitational forces, the clumpiness tended to aggravate instead of to even out. Since matter attracts matter, denser regions exerted more attraction on their surroundings pulling in more matter and so on, giving rise to the first generations of stars and galaxies .

Matter (stars, gas, dust) tends, because of gravitation, to spiral inward, so most older stars are to be found in a more or less rounded