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Thursday, 1 January 2015

Happy New year! There's a monster in the skies....

No, the title doesn't refer to a terribly hung over Santa who'll dive bomb anyone who makes too much noise. If that happens to anyone it was nothing to do with me. I've been to 'busy' to set up anything like that...

And, while surfing the net hungover, I've come across a paper on something a lot scarier than a drunk Santa*. 

The night sky hides many secrets, and one of them is a cosmic force of god like hunger that'd make Cthlhu wee itself: It's know to astronomers as Sagitarius A*, and it's a black hole. A black hole as big as a small solar system.

Above: A close up view of the patch of sky where the beast lives, courtesy of the University of Illinois.

The existence of this gaping chasm in the universe isn't news. It's swallowed uncounted suns, planets, nebula... that kind of thing leaves subtle signals - like whole stars being pulled toward its maw. But it's 35,000 26,000light years away. That's further than the distance to an open shop when you've had a Christmas day toilet roll shortage. It couldn't possibly affect us, right?

According to this paper, yes, yes it can. Here's the abstract: 

Sagittarius A* Rivaled the Sun in the Ancient X-ray Sky

Sagittarius A*, lying the Galactic Center 8 kpc from Earth, hosts the closest supermassive black hole known to us. It is now inactive, but there are evidences indicating that about six million years ago it underwent a powerful outburst where the luminosity could have approached the Eddington limit. Motivated by the fact that in extragalaxies the supermassive black holes with similar masses and near-Eddington luminosities are usually strong X-ray emitters, we calculate here the X-ray luminosity of Sagittarius A*, assuming that the outburst was due to accretion of gas or tidal disruption of stars, both scenarios having been considered to trigger the previous outburst. We show that in both cases Sagittarius A* could precipitate on Earth an X-ray irradiance comparable to that from the current quiescent sun. The irradiance in harder energy band  surpasses that from an X-class solar flare, and the irradiation 
timescale is also much longer......

To translate some of the science-ese: Sagittarius A* doesn't eat so much as scoff. Very, very messily. The mess of superheated gas it leaves could be as bright as the Sun, as seen from Earth. But not bright in nice visible light, oh no. In X-rays. 

Yep, the same X-rays that're inside the airport scanner. The Scanner you absolutely shouldn't get into and switch on for kicks.
There's a reason why the dentist disappears behind a lead lined wall when he X-rays your teeth: Even small doses of X-rays can be dangerous if they're able to build up over time. If the dentist has to hide from a thirty second dose a  few times a day then imagine the effect a second Sun's worth of X-rays would have had on ancient Earth...

Fortunately, as the paper describes, the beast is currently on a starvation diet. But we know that it's not completely quiet - we can see the effect of its snacking on the surrounding clouds of gas....

Above: The light echoes from the huge black hole's outbursts, caught here rippling over nearby gas clouds, over the course of twelve years. Image courtesy of NASA

If it were more active six million years ago, as the paper suggests, it'd definitely have had an effect on the ancient Earth. But if that's the case then it probably influenced the evolutionary processes that led to us - So we may owe our very existence to the monster in the sky above us.

Observing the way stars, planets, and clouds of gas behave in the vicinity of the giant maw gives us a sort of lab for studying the most extreme conditions warped of space-time: We see gas clouds moving at incredible speeds, and mysterious objects appearing out of nowhere.

It might be a slightly less comforting sky with such a grandold monster in it.

But it's also a more interesting one.

* I only found one thing though.

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