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Friday, 6 July 2012

Young, angry, star kicking out......

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Image above: Our sun, seen in three different wavelengths of electromagnetic radiation, by the SOHO spacecraft. Image courtesy of NASA/ESA.

We think of our Sun as safe, stable, friendly, life giving .........

Odd that, considering it's basically a gigantic nuclear explosion, hanging in space.

This week it's been acting up, with a sunspot cluster giving off a series of powerful M-class flares [1], causing radio blackouts here on Earth - despite our planets protective magnetic field [2]. But, even though an M-class [3] flare has the energy of millions of nuclear weapons, really they're nothing....

Video above: Active sunspot region 1515, seen by the Solar Dynamics Observatory, as it spits out a whole bunch of powerful flares over the last week. True, even from a hundred and fifty million kilometres away they had enough force to disrupt radio communications. But as these things go this is barely a grumble. Video courtesy of  NASA.

Our Sun is content, these days, to just hint at it's power: Killing off the odd satellite [4], blowing out a power grid [5], and sparking Auroras.

But imagine, four and a bit billion years ago, when it had full blown temper tantrums...

An international collaboration, between ESA's XMM-Newton space telescope, NASAs Chandra space telescope, and JAXA's Suzaku space telescope, has examined a young star [5] of a similar type to the Sun, 1300 light years away: V1647 Ori.

Image above: The grumpy young protostar. V1647 Ori. Image courtesy of the Gemini observatory.

Through this infant Sun-alike we're given a glimpse into our star as it might have been in it's youth: An angry, twitchy, temper tantrum throwing, ball of nuclear fire. Much worse than the... um... friendly... ball of nuclear fire we know today.

Ori is a difficult child*: It's a protostar, a star at that age where it's still forming from the yoke of it's nebula, spinning at incredible rates, and spitting out enormous X-ray flares. Like most young stars Ori has a protoplanetary disc around it, and the growing star is sucking down matter from the disk at up to three hundred kilometres a second. It's also crowning itself with twin pillars of plasma, thrown out of it's poles by an intense magnetic field. So there's plenty of scope for something messy to happen... and it has been.

The space telescopes have followed Ori through two awe inspiring tantrums: From 2003 to 2006, and again from 2008 onwards, Ori has been glutting down and vaporising more matter than usual, throwing out a surge in X-ray emissions, and wreathing itself in plasma at temperatures of fifty million degrees Celsius. These are temper tantrums of unimaginable proportions - certainly powerful enough to sterilise Earth if the Sun were to have a fit like that today. But that's vanishingly unlikely, and what we see from Ori is the first evidence that the rate at which matter falls into the star, and the intensity of its X-ray surges, are directly related

The intense magnetic field seems to be the engine behind this. To explain, I'm recruiting Paul Cassack, of the university of west Virginia:

Video above: Paul Cassack gives a nice, simple, explanation, of how magnetic reconnection heats a plasma. Rubber bands are involved. Video courtesy of The University of West Virgina.

Being young, and fast spinning, Ori has a far, far, stronger field than a more mature star. The magnetic field is connected to the protoplanetary disk, but the star and disk spin at different rates. This forces the field lines to continuously break and re-connect, and since these have a lot more power in them than your fridge magnet, the breaking and re-connecting heats plasma near the stars surface. At the same time, stuff from the protoplanetary disk is crashing into Ori's photosphere, raising even more mayhem.

Video above: A simulation of V1647 Ori, sat in the middle of it's protoplanetary disk. The wiggly, glowing lines, connecting Ori to its disk are where the young stars magnetic field is channelling disk matter down onto the surface - resulting in enormously powerful hotspots, lots of x-rays, UV, high energy particles, millions of degrees of heat....  the kind mess and fury that only something very young and powerful can put out. Video courtesy of ESA.

The orbiting observatories also found an X-ray emission that rises and falls, heartbeat like, every day or so. There seems to be a pancake shaped hotspot on one side of Ori, that spins into and out of view as the star turns. The best candidate for what's causing this stellar nappy rash is a stream of disk matter, crashing into the surface, giving rise to a non stop fire-storm. But this observation also tells us how fast the star is turning - and if it were spinning just a little faster, it would tear itself apart!

Kids eh?

This stroppy phase won't last forever - if it did the Sun would still be doing it, and Earth would be an airless radioactive ball of rock. But while it does we get an enlightening glimpse into our own solar systems past, and a reminder:  The force that drives (almost) all life on Earth isn't just a nice ball of light in the sky....

* Every parent thinks their child is difficult when they say 'bed time' and their offspring says "Nu-nu-nu oooooOOO!", and breaks their toys. Imagine if your child was over a million miles across, hot enough to melt through any form of matter, and could crunch whole planets. A bic-bic and story probably wouldn't cut it.

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