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Monday, 27 April 2015

Baby planet Vs black hole, an underdog story of cosmic proportions...

Baby planets Vs Giant black holes

I'll admit I have a real soft spot for the underdog, but I didn't expect it to be touched by a celestial encounter twenty six thousand light years away. That said I didn't expect Madonna to still be going,  terminator like, in the year 2015. So much for my powers of prediction, and this story begins with astronomer's powers of prediction being a bit off as well....

The beast in the night.

Above: A map of the Galactic Centre, courtesy of the Naval Research Laboratory

You may or may not know that in the centre of our galaxy is something that deserves the description 'cosmic monster': A black hole the size of a small solar system. Last year astronomers were wetting themselves with excitement* - a gas cloud, named simply 'G2' was heading for a close pass of the maw. A black hole's gravitational grasp extends far beyond its edge, and the gas cloud (which, on account of it being, y'know, gas, should be pretty flimsy) wasn't expected to pass unscathed. Astronomers are partial to a spot of massive cosmic violence, and in particular they hoped we'd get to see the famous spaghettification effect in action

Above: To explain spaghettification, and the myriad other ways black holes are bad for ones health, I'll hand you over to the always dependable Neil DeGrasse Tyson.

G2 fell towards the gigantic black hole, raced around its edge.... and nothing much happened. The object seemed slightly more spread out, but it was pretty spread to start with. This was both slightly embarrassing and fairly weird for astronomers. After all, it's not as if they can ask a titanic gap in space time for their money back. It seemed as though G2 wasn't what it looked like.

Above: A simulation of what was expected to happen to the G2 'cloud'.

 Now Michela Mapeli and  Emanuele Ripamonti have a possible explanation: Perhaps G2 isn't just a weakly held together cloud of gas. Perhaps its an embryonic planet (link here).

True, planets don't look much like gas clouds, but the planetary embryo of a gas giant is (according to theories) a smeared out blob of gas and dust, denser towards the middle, but without a definite core object until it is mature. There's also the fact that the galactic core is a fat less friendly place than our quite suburb here near the galactic rim: The core is full of massive, super bright, suns that blast out high energy radiation -  radiation which evaporates clouds of gas from almost any surface it strikes.  At the same time the tidal forces from the gigantic central black hole can strip huge blobs of matter off anything not firmly held together, even hundreds of millions of kilometres away. G2 might well be a planetary embryo that has been distorted by these ferocious conditions.

Above: A simulation of planetary embryos forming in a protoplanetary disk. Courtesy of Our Universe Visualised.

A gas giant embryo, in a state halfway between a collapsing gas cloud and a planet, could have all the right properties to explain what has been seen. And if that is the case, it raises some very interesting possibilities - possibilities the paper also touches on: This embryo might be a sign that some of the stars surrounding the black hole aren't formed naturally, but are instead children of the black hole. Giant planets and stars have certain things in common when they form, and something analogous to the process that formed the giant planets in our solar system billions of years ago might be happening in the swirling matter surrounding the black hole, giving birth to stars, planets, brown dwarfs, all living a crowded existence, right on the edge of the greatest destructive force ever discovered.

It's an idea that has a nice yin-yang symmetry to it -  a force of great destruction creating so many things. But All we know for sure right now is that, whatever G2 actually is, it's tougher than anyone expected. Tough enough to tease a super massive black hole and survive, at any rate.

Elsewhere in the universe:

MESSENGER takes the highest resolution image of Mercury ever.

I've been saying for a while now that the MESSENGER probe is doomed -it's out of fuel, the effects of the Sun's gravity will eventually smash it into Mercury's surface, and yet it has just taken this:

Above: Yes, I know this is just a bunch of craters, but it's a bunch of craters taken by a doomed space probe just 8000 meters aboive the surface of Mercury - this is probably the highest resolution image we'll get of the innermost planet in our lifetimes. Courtesy of NASA.
It doesn't look like much, but it was taken by the probe just 8000 meters above the surface, and it's the highest resolution image ever taken. the MESSENGER team are using the very last of the helium gas they've MacGyvere'd as propellant to buy the probe another week before it slams into Mercury....

Above: MacGyver, teaching kids that you can build weapons out of household objects since I was a boy. Why'd you think I got into science? Yes, it's the bloke from Stargate SG1. And if those references are too nerdy for you... well, you might actually be someone with a social life.
Elsewhere on the internet:

Hydrothermal vents can produce prebiotic chemicals

Electric solar sail could ship water from the asteroid belt?

First laser cannons, now rail guns for the US navy

* With a few rare exceptions this is not literally true.

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