What Does It Mean To Be ‘Star Stuff’?

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The Tycho supernova remnant. This type of structure is all that remains after a massive star dies, releasing the chemical building blocks of life and planetary systems into space. Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al.

Courtesy of Vanessa Janek @ Universe Today:

At one time or another, all science enthusiasts have heard the late Carl Sagan’s infamous words: “We are made of star stuff.” But what does that mean exactly? How could colossal balls of plasma, greedily burning away their nuclear fuel in faraway time and space, play any part in spawning the vast complexity of our Earthly world? How is it that “the nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies” could have been forged so offhandedly deep in the hearts of these massive stellar giants?

Unsurprisingly, the story is both elegant and profoundly awe-inspiring.

All stars come from humble beginnings: namely, a gigantic, rotating clump of gas and dust. Gravity drives the cloud to condense as it spins, swirling into an ever more tightly packed sphere of material. Eventually, the star-to-be becomes so dense and hot that molecules of hydrogen in its core collide and fuse into new molecules of helium. These nuclear reactions release powerful bursts of energy in the form of light. The gas shines brightly; a star is born.

The ultimate fate of our fledgling star depends on its mass. Smaller, lightweight stars burn though the hydrogen in their core more slowly than heavier stars, shining somewhat more dimly but living far longer lives. Over time, however, falling hydrogen levels at the center of the star cause fewer hydrogen fusion reactions; fewer hydrogen fusion reactions mean less energy, and therefore less outward pressure.

At a certain point, the star can no longer maintain the tension its core had been sustaining against the mass of its outer layers. Gravity tips the scale, and the outer layers begin to tumble inward on the core. But their collapse heats things up, increasing the core pressure and reversing the process once again. A new hydrogen burning shell is created just outside the core, reestablishing a buffer against the gravity of the star’s surface layers.

While the core continues conducting lower-energy helium fusion reactions, the force of the new hydrogen burning shell pushes on the star’s exterior, causing the outer layers to swell more and more. The star expands and cools into a red giant. Its outer layers will ultimately escape the pull of gravity altogether, floating off into space and leaving behind a small, dead core – a white dwarf. Continue reading

IPCC climate change report: averting catastrophe is eminently affordable

For those people that choose growth over the sustainability of our planet for future generations are malevolent fools. Not only do we need to look at renewables but alternative energies need to be sought and government black projects need to released to the public. Courtesy of Damien Carrington @ The Guardian:

Catastrophic climate change can be averted without sacrificing living standards, according to a landmark UN report published on Sunday. It concludes the transformation required to a world of clean energy and the ditching of dirty fossil fuels is eminently affordable.

The authoritative report, produced by 1250 international experts and approved by 194 governments, dismisses fears that slashing carbon emissions would wreck the world economy. It is the final part of a definitive trilogy that has already shown that climate change is “unequivocally” caused by humans and that, unchecked, it poses a grave threat to people and could lead to lead to wars and mass migration.

Diverting hundred of billions of dollars from fossil fuels into renewable energy and cutting energy waste would shave just 0.06% off expected annual economic growth rates of 1.3%-3%, the Intergovernmental Panel on Climate Change (IPCC) report concluded. Furthermore, the analysis did not include the benefits of cutting greenhouse gas emissions, which could outweigh the costs. The benefits include reducing air pollution, which plagues China and recently hit the UK, and improved energy security, which is currently at risk in eastern Europe after the actions of major gas-producer Russia in Ukraine.

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The new IPCC report warns that carbon emissions have soared in the last decade and are now growing at almost double the previous rate. But its comprehensive analysis found rapid action can can still limit global warming to 2C, the internationally agreed safety limit, if low-carbon energy triples or quadruples by 2050.

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