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A Star is born : The simplest of questions often takes us down some fabulous paths. How is a star created? It seemed so basic - well dust gets together in a supernova, they coalesce and gravity pulls it all together. If there is enough matter, it gets superdense and fusion is sparked off. Well that is the basic understanding. Fascinating how simple concepts make it possible for us to live. Or is it as simple as we are making it out to be?

Protostars : The core of the cloud collapses faster than the outer parts, and the cloud begins to rotate faster and faster to conserve angular momentum. When the core reaches a temperature of about 2,000 degrees Kelvin, the molecules of hydrogen gas break apart into hydrogen atoms. Eventually the core reaches a temperature of 10,000 degrees Kelvin, and it begins to look like a star when fusion reactions begin. When it has collapsed to about 30 times the size of our sun, it becomes a protostar.

Equiblirum : When the pressure and temperature in the core become great enough to sustain nuclear fusion, the outward pressure acts against the gravitational force. At this stage the core is about the size of our sun. The remaining dust envelope surrounding the star heats up and glows brightly in the infrared part of the spectrum. At this point the visible light from the new star cannot penetrate the envelope. Eventually, radiation pressure from the star blows away the envelope and the new star begins its evolution. The properties and lifetime of the new star depend on the amount of gas that remains trapped. A star like our sun has a lifetime of about 10 billion years and is just middle-aged, with another five billion years or so left.

Webb science : Groups of stars make up galaxies, while planets and ultimately life arise around stars.  Although stars have been the main topic of astronomy for thousands of years, we have begun to understand them in detail only in recent times through the advent of powerful telescopes and computers. A hundred years ago, scientists did not know that stars are powered by nuclear fusion, and 50 years ago they did not know that stars are continually forming in the Universe.  Researchers still do not know the details of how clouds of gas and dust collapse to form stars, or why most stars form in groups, or exactly how planetary systems form.

Powerhouse : At present, the only way we have of initiating hydrogen fusion is to use nuclear fission: the so-called "hydrogen" bomb uses the explosion of a plutonium bomb to (very briefly) ignite uncontrolled fusion of the hydrogen isotopes deuterium and tritium.  We cannot control fusion, although much research on the subject has been conducted over the past 40 years.  The Sun dodges these problems and fuses hydrogen via its sheer, overwhelming bulk.  The pressure at its center squeezes the gas there to fourteen times the density of lead.  The temperature is 15 million K°.

H/t to +Cyndi S. Jameson for pointing me in this direction.

Sources and references:

Northwestern : http://faculty.wcas.northwestern.edu/~infocom/The%20Website/birth.html

BBC: http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/living_future/8_big_bang1.shtml

Scientific American: http://www.scientificamerican.com/article/how-is-a-star-born/

ESA: http://www.esa.int/esaKIDSen/SEMY06WJD1E_OurUniverse_0.html

NASA (James Webb) : http://jwst.nasa.gov/birth.html

#science #scienceeveryday #stars  

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Water from the Sun? : This is a fascinating story of how we have been tracking the water in the Solar system, on our Moon and also from other stars.... Now we hear that our own Sun may be spraying water into Space. Sounds like Science Fiction? Read on....

Article Extract: When the solar wind blows against oxygen-rich rocks, says Charles Choi for Space.com, the combination of hydrogen and oxygen can cause water to form. This process could play out anywhere with the right types of rocks, from the surface of the Moon to a solitary mote of interplanetary dust. As interplanetary dust is thought to have rained down on early Earth, it is likely that the stuff brought water to our planet, although it is difficult to conceive how it could account for the millions of cubic kilometres of water that cover Earth today. "In no way do we suggest that this was sufficient to form oceans," says Ishii. But it could help explain why our solar system is actually quite wet.

Water from the Sun : A recent discovery may shed some new light on the origin of lunar water.  Researchers conducting detailed examination of tiny fragments of glass in soil returned by the Apollo astronauts found the molecule hydroxyl (OH) present in the glass.  Interestingly, the isotopic composition of these OH molecules indicates the bulk of the hydrogen comes from the Sun, not from cometary and asteroidal impacts.

Star Found Shooting Water "Bullets" : Seven hundred and fifty light-years from Earth, a young, sunlike star has been found with jets that blast epic quantities of water into interstellar space, shooting out droplets that move faster than a speeding bullet. The discovery suggests that protostars may be seeding the universe with water. These stellar embryos shoot jets of material from their north and south poles as their growth is fed by infalling dust that circles the bodies in vast disks. "If we picture these jets as giant hoses and the water droplets as bullets, the amount shooting out equals a hundred million times the water flowing through the Amazon River every second," said Lars Kristensen, a postdoctoral astronomer at Leiden University in the Netherlands.

Article Link: http://www.smithsonianmag.com/smart-news/sun-spraying-water-space-180949516/

Water from the Sun : http://www.airspacemag.com/daily-planet/water-from-the-sun-77291080/

Star Found Shooting Water "Bullets" : http://news.nationalgeographic.com/news/2011/06/110613-space-science-star-water-bullets-kristensen/

From +Philip Plait's article in +Slate : http://blogs.discovermagazine.com/badastronomy/2011/10/24/a-thousand-oceans-of-water-surrounds-a-nearby-star/#.UvDObrRjml4

Linked paper: http://www.pnas.org/content/early/2014/01/16/1320115111.abstract?tab=author-info

Pics courtesy: Discovermag, Smithsonianmag, Hdwallpapers, Natgeo.

#sun #water #h20 #stars #space #astronomy  
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2014-02-04
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Thorne-Zytkow objects : Still not 'news' but astronomers have a candidate for a Thorne-Zytkow object. What is it? When a superdense neutron star is captured by a red giant or supergiant star. One star is then nested in the other. This was first theorized in 1975, but no such star had been found...yet..... read on!

Article Extract: Once the neutron star is eaten, it settles in the core of the supergiant, interrupting normal fusion processes inside the star’s guts. This, according to the theorists, should create a very specific chemical signature in the “host” star’s chemical make up. What’s more, there should be a few dozen Thorne-Żytkow object specimens in our galaxy.

Emily Levesque, of the University of Colorado in Boulder, has reported the discovery of another Thorne-Żytkow object candidate, the strongest candidate to date. Levesque announced her discovery at the 223rd American Astronomical Society meeting in Washington, D.C., but fell short of naming the particular star as her research has yet to be published in a peer-reviewed journal.

What is known, however, is that the star is one of 22 supergiants surveyed in the Small Magellanic Cloud, a dwarf galaxy next door to the Milky Way, by the Magellan telescopes in Chile. The mystery oddball stellar behemoth has elevated quantities of lithium, rubidium and molybdenum — elements that are theorized to arise from the presence of a neutron star inside a red supergiant, forcing the old star to carry out different forms of fusion processes.

Article Link: http://news.discovery.com/space/astronomy/has-the-weirdest-star-in-the-universe-been-discovered-140107.htm

Nature Article : http://www.nature.com/news/bizarre-star-could-host-a-neutron-star-in-its-core-1.14478

Abstract from paper: http://adsabs.harvard.edu/doi/10.1086/181839

Wikipedia link: http://en.wikipedia.org/wiki/Thorne%E2%80%93%C5%BBytkow_object

Pics from Nature : Thorne-Zytkow objects could form when a red giant swallows a neutron star (right). John Foster/Science Photo Library

#stars #science #physics #astronomy  
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Where do the elements come from ? : The early Universe had only subatomic particles, which combined to form the very light elements, largely Hydrogen and Helium. It is theorized that the early Universe was a very dark place filled with largely Hydrogen gas. How do we know this? We can still see the echoes from these first atoms in the Cosmic Microwave Background. All the other elements came from the fusion reactions in stars.

Article Extract: The atoms left over by the big bang were gravitationally attracted to one another and condensed into huge clouds . The gravitational pressure on the centers of these clouds heated them to temperatures of millions of degrees. This led to the fusion of hydrogen into helium. Stars were born.

Stars fuse lighter elements to form heavier ones.... Inside stars, Hydrogen is converted into Helium, through nuclear fusion – and some matter is turned in to energy in the process. Why does this produce energy? Since some of the mass in creating the heavier element was converted into Energy (remember E=mc2). This is called Nucleosynthesis. These reactions continue to form Li, Be, B, C, N, O, F, Ne.... and so on. Upto Fe (Iron).

Until the time the Star starts creating Iron, the star is still not dense enough for gravity to overcome the nuclear reactions in the star. Once Iron is formed, the density of the star is so great, it collapses on itself due to gravity.

So where do the other heavier elements come from? : The heaviest elements are created in supernovae, the fantastic death of supergiant stars. As the core of the supergiant becomes saturated with iron, its pressure and temperature increase. Eventually, the blackbody radiation from the core produces gamma rays powerful enough to break apart the iron atoms in the core. This further increases the pressure to a point where electrons and protons are fused into neutrons. This releases lots of energy in the form of neutrinos. The core cools and contracts; the inner shells rush to fill the void. As the core reaches nuclear density it become rigid and even bounces back a little. When the onrushing material feels this bounce, it creates a wave. As the wave spreads to outer, less-dense regions, it speeds up. Soon it is a shock wave and combines with the wave of neutrinos. The star is doomed. This process blows the star apart releasing 10^46 joules of energy. This shock wave is the only place hot and dense enough to fuse elements heavier than iron, elements up to and including uranium.

Main Source: http://www.haystack.mit.edu/edu/pcr/Astrochemistry/3%20-%20MATTER/nuclear%20synthesis.pdf

How Stars make elements: http://www.foothill.edu/attach/938/Nucleosynthesis.pdf

The Evolving Universe: http://www.mnh.si.edu/exhibits/evolving-universe/bigbang/

Making the elements in the Universe: http://scienceblogs.com/startswithabang/2009/06/25/making-the-elements-in-the-uni/

Wikipedia link: http://en.wikipedia.org/wiki/Stellar_nucleosynthesis

Chemical composition of Stars: http://spiff.rit.edu/classes/phys240/lectures/elements/elements.html

Supernova: http://en.wikipedia.org/wiki/Supernova

Popsci Link: http://www.popsci.com/science/article/2012-12/our-solar-system-formed-ashes-countless-stars-not-one-supernova-study-says

Pics courtesy: Wikipedia and Wikimedia. Youtube video gif created from NOVA (BBC Science).

#science #stars #elements  
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2013-11-02
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Supernova : A star with a mass of more than eight times of the Sun releases tremendous energy when it is dying and undergoes a supernova explosion. The shockwave caused by the supernova explosion expands, having a strong impact on the composition and physical state of surrounding interstellar materials. It also emits kinetic energy into interstellar space. "Galactic winds" blasting out a large amount of gas are often observed in galaxies where explosively active star formations take place. The energy source of such galactic wind is also thought to be many supernova explosions.

The fusion reactions in the stars convert Hydrogen to Helium, Helium to Carbon, Oxygen and so on including Neon and finally to Iron. After which the star starts to contract due to the mass and gravity, losing more and more energy...

In a fraction of a second, the iron-rich core of the star collapses, from a sphere roughly the size of the Earth (radius 6000 km) to a ball of radius only 50 kilometers or so. As the core shrinks, the protons and electrons in it are crushed together to form neutrons. Neutrons are peculiar particles: they resist being pressed together closely ("neutron degeneracy pressure"). The core collapse halts when the pressure of the "neutron gas" reaches a critical level. The collision of these layers with the core creates a shock wave which shoots back outwards at thousands of kilometers per second. The shock wave rips through the outer layers of the star, heating them up to millions of degrees and shoving them outwards violently.

The expansion velocity? Approximately 13 kilometers per second!

Pic on Left: In our own galaxy, we can look at the remnants of a supernova which exploded in the year 1054: the Crab Nebula. Pictures taken in 1973 and 2000 reveal the continuing expansion of the gas. http://spiff.rit.edu/classes/phys230/lectures/sn/sn.html

Pic on Right: This two-frame animation is an excerpt from a more detailed online movie illustrating the events following the supernova 1987A outburst. The blue ring is previously observed material ejected from the star thousands of years ago. The expanding orange and yellow shell is multimillion degree, X-ray emitting gas produced by the explosion. Portions of the blue ring light up when struck by the X-ray shell. http://science.nasa.gov/science-news/science-at-nasa/2000/ast11may_1m/

Article Link: http://www.sciencedaily.com/releases/2013/08/130813101012.htm

Source: http://science.nasa.gov/science-news/science-at-nasa/2000/ast11may_1m/

Additional Source: http://hubblesite.org/newscenter/archive/releases/2005/02/image/g/

Wikipedia link: http://en.wikipedia.org/wiki/Supernova

Reference: http://spiff.rit.edu/classes/phys230/lectures/sn/sn.html

#science #scienceeveryday #supermova #star #explosion #fusion #nebula  
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2013-08-13
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Travelling to a Star : New NASA Probe to the Sun planned : Slated to launch no later than 2018, Solar Probe Plus will repeatedly plunge through the sun's superhot outer atmosphere, called the corona, coming as close as 4 million miles from the star's fiery surface.

The probe's first pass by the sun will occur two months after launch, at a distance of 15 million miles from the star. Over the next several years, swing-bys of Venus will slowly tweak the probe's trajectory, so that Solar Probe Plus gradually gets closer to the sun during each successive orbit. By 2024 the probe's path will be eight times closer to the sun than the orbit of Mercury.

Flying so close to the sun means things will really heat up for the plucky probe, so NASA has outfitted the craft with a cutting-edge carbon-composite heat shield. Ultimately, dive-bombing the sun should help scientists solve a number of mysteries about our nearest star.

Article link: http://news.nationalgeographic.co.in/news/2010/09/100909-science-space-sun-new-nasa-solar-probe-plus-dive-bomb/

The Wikipedia link: http://en.wikipedia.org/wiki/Solar_Probe_Plus

NASA mission page: http://science1.nasa.gov/missions/solar-probe/

Solar Probe Plus detailed information : http://solarprobe.jhuapl.edu/

#science #scienceeveryday #sun #space #star #solarprobe #nasa #probe #solar  
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2013-08-07
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Supernova : Many thousands of years ago, a large star went Supernova. The light from this even was seen on Earth by humans only around a 1000 years ago. It was reported as a bright star which appeared briefly in the sky and then disappeared. I can imagine what it looked like in the sky! the remnants of this supernova is what we see as the Crab Nebula today.

The search for historical supernovae started at that moment: seven other historical sightings have been found by comparing modern observations of supernova remnants with astronomical documents of past centuries. Given its great distance, the daytime "guest star" observed by the Chinese could only have been a supernova—a massive, exploding star, having exhausted its supply of energy from nuclear fusion and collapsed in on itself. Recent analysis of historical records have found that the supernova that created the Crab Nebula probably appeared in April or early May, rising to its maximum brightness of between apparent magnitude −7 and −4.5 (brighter than everything in the night sky except the Moon) by July. The supernova was visible to the naked eye for about two years after its first observation.

The Crab is a fantastically complicated place, with a lot going on at once. It’s hard sometimes to know what’s what. But we do get hints, and we’re getting a glimpse of its three-dimensional structure, providing essential clues to the events we’re witnessing. Stars like these are what create nearly all the elements in the Universe besides hydrogen and helium. The iron in your blood and calcium in your bones came from stars like this that exploded billions of years ago. When we study objects like the Crab, we’re learning not just about astronomy, but literally about where we came from.

Article link and source: http://blogs.discovermagazine.com/badastronomy/?p=21872#.UfonrG2NAUg

Additional Source: http://en.wikipedia.org/wiki/Crab_Nebula

More recent news of Pulsars emanating from the Crab Nebula : http://www.nature.com/nature/journal/v482/n7386/full/nature10793.html

#science #scienceeveryday #crabnebula #supernova #space #star #messier #nebula #crab  

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Colliding Neutron Stars could be the source of Gold : On June 3, 3.9 billion light-years away, two incredibly dense neutron stars— bodies that are each about 1.5 times the mass of the sun but just the size of mere cities—collided. Scientists studying the event say it solves an enduring mystery about the formation of elements in our universe.

Over the next few days, telescopes in Chile and the Hubble Space Telescope turned their attention to that region of space. Today, Berger and colleagues announced at a press conference in Cambridge, Massachusetts, that their analysis reveals that neutron star collisions are responsible for the formation of virtually all the heavy elements in the universe—a list that includes gold, mercury, lead, platinum and more. Though many scientists had long argued that supernova explosions were the source, he says his team—which includes Wen-fai Fong and Ryan Chornock of the Harvard astronomy department—have evidence that supernovas aren’t necessary. These neutron star collisions produce all elements heavier than iron, he says, “and they do it efficiently enough that they can account for all the gold that's been produced in the universe.”

Smithsonian Article link: http://goo.gl/xMhG8

Research Link: http://arxiv.org/abs/1306.3960

Pic illustration: Two neutron stars violently collide—potentially the sourse of all heavy elements in the universe, including gold. (Dana Berry, SkyWorks Digital, Inc.)

#neutronstar #space #gold #heavyelements #collision #grb #stars #astronomy #science #scienceeveryday  
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What is a Neutron Star? : It is the remnants of a Supernova and the subsequent gravitational collapse of a massive star. It is only prevented from collapsing on itself by Pauli's exclusion principle.  Neutron stars typically arise from the collapse of massive stars. These stellar remnants are made almost entirely of neutrons, and are incredibly dense...about the mass of the sun, but squeezed into a sphere just a few miles wide.

A neutron star is so dense that one teaspoonful of its material would have a mass over  900 times the mass of an large airport. This star spins around at dizzying speeds of 200 to 600 times per second!

Researchers have focused on the extremely volatile surfaces of neutron stars. In a process called accretion, white-hot plasma pulled from a neighbouring star rains down on the surface of a neutron star with incredible force — equivalent to 100 kilograms (220 pounds) of matter slamming into an area the size of a coin every second. As more plasma falls, it forms a layer of fuel on the neutron star’s surface that builds to a certain level, then explodes in a thermonuclear fusion reaction. This explosion can be detected as X-rays in space: The bigger the explosion, the greater the X-ray intensity, which can be measured as a spike in satellite data.

On the basis of current models, the matter at the surface of a neutron star is composed of ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps between them.

Pic details: on right Cross-section of neutron star. Densities are in terms of ρ0 the saturation nuclear matter density, where nucleons begin to touch.

Pic on left: NASA artist's conception of a "starquake", or "stellar quake".

Wikipedia reference: http://en.wikipedia.org/wiki/Neutron_star

Nature reference: http://www.nature.com/nature/journal/v494/n7435/full/494046a.html (behind paywall)

MIT reference: http://web.mit.edu/newsoffice/2012/model-bursting-star-0302.html

#science #scienceeveryday #star #astronomy #neutronstar
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2013-05-27
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