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| Messier 57 The Ring Planetary Nebula in the Constellation Lyra - taken through my 127mm Meade refractor at F6 - 10 x 3 minute exposures at ISO800 using my Canon 600D DSLR -guided with my QHY5-11 camera. The nebula through an eyepiece looks like a small grey smoke ring, a digital camera brings out the colours of the expanding shells of gas and dust. |
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First may I advise my readers that I have no real expertise in the fields of physics, astrophysics, chemistry or divinity - so I am sure many of you will hold differing views as to the validity and accuracy of the following information. It is however my best shot at understanding and explaining the wonderful and perplexing nature of existence.
Nothing lasts forever, not you or me! Well thats not altogether true. As far as I understand it, the bits and pieces of matter, the simplest nucleic particles, from which we and everything else in the universe were eventually created, do.
Apparently, some 13.5 billion years ago and from the energy, neutrons and protons created in the first few seconds of the 'Big Bang' - the simplest neutral atoms of Hydrogen, Helium, Deuterium and Lithium were created as the protons, neutrons and electrons within the maelstrom of plasma that was then the whole universe, cooled sufficiently for them to combine. Since this time, no new protons or neutrons have been created. In certain circumstances, protons can change to become neutrons and viceversa but only if the process allows universal energy-mass equilibrium to be maintained.
The more complex atoms, further up the periodic table, like the billions of carbon and oxygen atoms within our bodies, were synthesized much later in stars from the basic ingredients of atoms of Hydrogen, Helium and Lithium.
After about 550 million years the first stars were formed by the gravitational collapse of the clouds of hydrogen and helium atoms and at their dense and consequently hot cores nuclear fusion began. 'Twinkle twinkle littele star' but not forever!
A star shines for a very long time because of nuclear interactions at its core. At its simplest, 4 hydrogen protons fuse together to form one helium 4 nucleus and as a result of the process there is a release of photons ( particles of light). This process continues as long as there is hydrogen to fuse and as a consequence the core accumulates helium. Eventually every star runs out of hydrogen and when there is sufficient helium at the core the star begins to fuse helium nuclei to form mostly carbon and oxygen. Sooner or later the helium is used, then lithium, carbon, neon, oxygen and finally all fuseable nuclear fuel is eventually depleted. What happens next depends upon the mass of the star.
The more massive the star, the faster it will deplete its nuclear fuel and the more extreme will be its metamorphosis.
Stars with a mass of more than eight times the mass of our sun will, on depletion of their nuclear fuel, suffer a massive gravitational collapse and release energy in what is described as a supernova. Depending only upon the mass of the progenitor star, a neutron star, a pulsar or a black hole will survive the cataclysmic explosion at the centre of an expanding shell of gas and dust. The Crab Nebula is an example of the aftermath of a supernova in AD1054.
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| My image taken with the Bradford Robotic Telescope |
Our sun is quite small and classified as a 'yellow dwarf' star. It is approximately 4.3 billion years old and will probably last another 4.3 billion years before it depletes its hydrogen and instead fuses helium.
Stars like our sun do not supernova, instead as they fuse helium they cool and consequently radiate light in the red part of the spectrum. One day, far in the distant future our sun will puff out a rarified stellar atmosphere and balloon into a red giant star. Eventually, when our sun depletes all its nuclear fuel, it will collapse and leave behind a white dwarf star and expanding shells of glowing gas and dust. A white dwarf is in fact the incredibly hot remenant of the progenitor star. White dwarfs are so hot that it has been estimated that their theoretical life, that is how long they would take to cool down and not radiate light and heat, is in the range of tens of hundreds of billions of years. In fact the universe is not old enough at 13.8 billion years for any white dwarf stars to have stopped shining.
The gas and dust shells glow because of interactions between the energetic photons emitted by the white dwarf and the atoms of matter forged in the nuclear reactions of the progenitor star. The glowing shells, observed in the eighteenth century were called 'planetary nebula' by William Herschel in 1790, although they have nothing to do with planets. Planetary nebula are ephemeral expanding and consequently diffusing clouds of atoms which eventually become unobservable after a few tens of thousands of years from their inception.
Over the following millenia, these atoms including the heavier elements transformed in the progenitor star, spread throughout the universe mixing with other atoms of matter and sometimes joining together to form more complex molecules. Gravity, at some time way in the future, may eventually cause these wayward and diffuse bits of matter to collapse and conglomerate to provide the building blocks required to create a new star and planetary system.
'The circle of life' works on extended timescales, but however slowly, the recycling of matter on the nuclear scale occurs throughout the universe. It applies to the atoms that make up the stars, planets, atmospheres, seas, rocks, plants, animals and us.
I like to think that in billions of years from now a few of my protons and neutrons may be fusing in a star igniting in a far corner of our galaxy or being bound in the DNA of a strange life form on an alien planet not yet formed. I guess in this way we are all immortal and inextricably linked to the cosmos.
All the atoms of my body and yours were recycled and transformed more than once in stars that burned bright millenia ago. What unknown histories we must carry in our atomic construction.
You do look, my son, in a moved sort,
As if you were dismay'd: be cheerful, sir.
Our revels now are ended. These our actors,
As I foretold you, were all spirits and
Are melted into air, into thin air:
And, like the baseless fabric of this vision,
The cloud-capp'd towers, the gorgeous palaces,
The solemn temples, the great globe itself,
Ye all which it inherit, shall dissolve
And, like this insubstantial pageant faded,
Leave not a rack behind. We are such stuff
As dreams are made on, and our little life
Is rounded with a sleep.
Prospero -The Tempest - William Shakespeare
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| An enlargement from my widefield image. In 5 billion years from now will an astro-imager on an alien world, light years from here, be photographing a planetary nebula that is the glowing remains of what was once a small yellow dwarf star around which there had been a small blue planet we knew as our home world Earth? |
Messier 57 is approximately 2300 light years distant from earth. The blue green colour within the ring is caused by the double ionised atoms of oxygen. The density of matter within the ring is astonishingly rarefied, probably comprising only a few atoms of oxygen per cubic metre. The outer ring glows red because of the presence of excited hydrogen and ionised nitrogen atoms.
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| NASA,
ESA, C.R. Robert O’Dell (Vanderbilt University), G.J. Ferland
(University of Kentucky), W.J. Henney and M. Peimbert (National
Autonomous University of Mexico) Credit for Large Binocular Telescope
data: David Thompson (University of Arizona) - HubbleSite Release Image: STScI-2013-13 - NASA's Hubble Space Telescope Reveals the Ring Nebula's True Shape |
Credits: NASA, ESA, Wikipedia and Telescope. Org
