The dark side of the Milky Way
The scientific briefing with Luke Boulter
The Milky Way is often depicted serenely floating through space, not causing bother and generally just rotating its solar systems contently. It is surprising then that at the epicentre of this placid giant is one of the most destructive and enigmatic forces in the known universe. Humanity has just got its closest glimpse at this massive executioner.
The Milky Way consists of approximately 3 billion stars and is so huge that it takes our sun approximately 200 million years to drift the entire orbit. It is surprising therefore that something which is seemingly so cumbersome and subdued can have the heart of a monster, the infamous black hole.
Black holes form when there is a massive distortion in space-time, making it ‘bend’. Imagine a thin rubber sheet (known as the space-time continuum). If you place an orange in the centre of the sheet it would begin to sag in the middle, this is effectively what a star does. Now consider putting a melon in the centre. The sheet would be distorted further; this is what occurs in space with objects like white dwarfs or neutron stars, each increasing the distortion respectively.
Consider then something 2.6 million times denser than the sun, and squeeze all of that matter into a space potentially as small as 93 miles wide (considering our sun’s mass is approximately 1.98892 _ 1030 Kg and measures at its equator 450,000 km wide). This hugely dense patch on space time causes not a slight distortion, but what is commonly considered to be a vast hole in very fabric of the space-time continuum.
The Black Hole as it became known in 1976 is so dense that nothing can escape it, not even light; any matter unlucky enough to venture near a black hole will be sucked in. In accordance to Einstein’s theory of relativity this matter will be compressed to a point of infinite density, which occupies virtually no space, this point is known as singularity.
So why am I telling you this? Well this week scientists, using 10 radio telescopes in America got a glimpse of the super-massive black hole in the centre of our own galaxy Sagittarius A* (pronounced Sagittarius A-star). The Sagittarius A* black hole was shown to have the mass equivalent to four million suns and occupies a distance less than that from earth to our sun.
The vogue of Black Holes began in 1971 when the first experimental evidence was captured by the Uhuru satellite. Uhuru detected X-rays coming from a star orbiting a massively dense region, possibly a very dense neutron star which had collapsed and formed a mini-black hole.
After this discovery the hunt was on for the super-massive black holes, like Sagittarius A*. This giant black hole really is a mystery, there is very little understanding how it formed and why these black holes are found at the centre of galaxies. The most inspiring theory is that they were in fact here first, before our Milky Way and other galaxies formed. Black holes are essentially the seeds of the galaxy; they are so dense that all of the stars and their solar systems were drawn together to form what we see today.
So how do you observe a massive and very empty hole? What will Sagittarius A* look like? Well, the truth of the matter is that nobody really knows. There are theories of what black holes should look like; the most popular concerns the event horizon. The black hole should have an aureole of shadow caused by matter and light being swallowed. Circulating this shadow would be a bright ring where any light that does make it past the black hole is deflected away by the super mass of the beast.
With increasingly high resolution telescopes, the black hole could soon be unmasked, which, according to Dr. Fred Low, Director of the US National Radio Astronomy Observatory, “would be final proof that a super-massive black hole is at the centre of our galaxy.”
The ultimate dream is to be able to observe the black holes as we observe passing meteors or distant moons. Marcus Chown envisions a circle of shadow surrounded by a brilliant light, the light being super heated matter falling to its inevitable doom at the point of singularity. Who knows? perhaps the wormhole theory will hold true, offering an intergalactic highway from our universe to the next.
Well there you go, we can see black holes, but what honestly does this contribute to humanity? Is trawling the skies for these phenomena necessary, or is it just a galactic waste of time? Well, there are those that question if black holes really do occur and, despite his grand visions for what we would actually see, Chown admits: “The truth is we don’t exactly know for sure that black holes exist”.
Essentially though, this research boils down to the innate human interest to explore, and the need to know what caused our creation. Technology is offering the opportunity to probe the cosmos and show humanity the forces we could only theorise about in the past. With these new images, we can see in glorious technicolor the hub of the night sky.
Whether we are soon to be surfing the intergalactic highway or just contently gazing at a fuzzy photo, one thing that cannot be over estimated is the importance of the black hole. This is dependent, however, on whether we confirm black holes do indeed exist.
If in the coming months and years they are pictured, then we can spend time watching these destructive fiends. If, however, it comes to pass that they in fact don’t occur, then be prepared for a scientific race to find the glue holding our galaxy together.
