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Nuclear Astrophysics

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Happy 4th of July to those in the U.S.A.

From the nucleosynthesis point of view, such stellar explosions are not only impressive because of their energy and complexity but they also synthesize elements and isotopes from the stars initial make-up and/or distribute them in the Galaxy. New stars and planetary systems are then formed from the "ashes" of such events.
 
Interstellar Explosions for the Fourth of July
As you enjoy fireworks this Fourth of July, what you won’t see are countless eruptions of light, plasma, gamma rays and superheated gasses dancing above your heads. These galactic explosions occur nonstop throughout the cosmos.

Click the link to see more of the biggest and brightest lightshows in the universe. http://go.nasa.gov/1NzdCty
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Good news for the Joint Institute for Nuclear Astrophysics!

The funding for this NSF Physics Frontier Center has been renewed for the third time. A remarkable achievement in these days of reduced funding and increased competition, not only rewarding the hard work of many highly motivated individuals but also underlining the importance and relevance of this research field.

Congratulations!!

http://www.jinaweb.org/
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Supernova remnant
 
Supernova Remnant: A long observation with Chandra of the supernova remnant MSH 11-62 reveals an irregular shell of hot gas, shown in red, surrounding an extended nebula of high energy X-rays, shown in blue. Even though scientists have yet to detect any pulsations from the central object within MSH 11-62, the structure around it has many of the same characteristics as other pulsar wind nebulas. The reverse shock and other, secondary shocks within MSH 11-62 appear to have begun to crush the pulsar wind nebula, possibly contributing to its elongated shape. (Note: the orientation of this image has been rotated by 24 degrees so that north is pointed to the upper left.)

Image credit: NASA/CXC/SAO/P. Slane et al.

#nasa #chandra #xray#astronomy #space #nebula #science #supernova

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Touchdown!

The comet lander Philae successfully attached itself to the surface of the comet.

A historical day: The first comet landing.

Congratulations!
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There is a star with a calculated age that is older than the universe. That might seem like a contradiction, but it's not.
The star HD 140283 is a subgiant star with an estimated age of 14.46 billion years. That might raise an eyebrow or two for those of you who remember that the age of the universe is estimated as 13.77 billion years. It would seem that this particular star, sometimes referred to as the Methuselah star is older than the universe.
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Star Seed

One of the big mysteries in cosmology is how supermassive black holes formed in the centers of galaxies. Did they form directly from large concentrations of matter and dark matter, or did they form when early stars collided and accreted into massive black holes? Another idea is that they may have formed from the collapse of supermassive stars. In this idea stars with masses of 10,000 Suns or more could have lived short, violent lives before their core collapsed into a massive black hole. It’s an interesting idea, but new research shows that such supermassive stars might have a different fate.

This new research has been published in the Astrophysical Journal, and it looks at computer simulations of early supermassive stars. The team ran simulations of primordial (population III) stars with masses around 55,000 solar masses. At this scale, a simple hydrodynamic model doesn’t work. You need to account for the effects of general relativity as well as things like photodissociation, where the intense light of a star can break apart the nuclei of atoms. The team found that such stars can only survive for about 1.7 million years before becoming unstable.

This isn’t too surprising, but what is surprising is that for stars around this mass instead of dying as a core-collapse supernova, which would produce a massive black hole, instabilities cause the star to rip apart completely, leaving no remnant core. What’s more, a good fraction of the star’s mass has been fused into “metals” or elements beyond hydrogen and helium. As a result, such stars could provide a mechanism for the early enrichment of heavy elements in the universe.

The authors go on to point out that such a stellar explosion might be observable in the distant universe. If such stellar explosions occurred, they would be seen in the near infrared, looking similar to supernovae with high redshift (around z = 20). But because of the intense mixing of elements in the star, the explosion would look distinctly different from usual supernovae. Right now we don’t have the ability to observe such explosions, but future missions such as the Euclid infrared telescope (scheduled to be launched in 2020) might be capable.

So we haven’t solved the mystery of supermassive black holes, but we may have discovered a new way for early stars to seed the universe with heavy elements.

Image: Ke-Jung Chen, et al.

Paper: Ke-Jung Chen et al. The General Relativistic Instability Supernova of a Supermassive Population III Star.  ApJ 790 162 (2014)
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Happy 100th Birthday, Sir Fred Hoyle

Today we celebrate the centenary of the birthday of one of the fathers of the field of nuclear astrophysics.

Being a remarkable and very inventive scientist, Sir Fred Hoyle and his science collaborators published a ground-breaking work in 1957, laying the foundation for research on the origin of the elements in stars and stellar explosions. Most of their ideas are still regarded as correct, although some change had to be made to certain details, accommodating new results and observations.

But Fred Hoyle not only worked on nuclear astrophysics, he was a person with many interests. He also coined the term "Big Bang", intended as a derogative expression for a concept he did not like.
(In fact, the 1957 paper was devised to refute the idea that all chemical elements were made in the Big Bang, as Oppenheimer and other scientists at that time thought. Later, this turned out to be correct, only the lightest elements H, He, Li, and Be stem from primordial times of the Cosmos. It did not do away with the Big Bang, though, as Fred Hoyle hoped.)

His many ideas and his often undiplomatic behaviour sparked many controversies, both scientifically and unscientifically.

Happy 100th Birthday to a remarkably productive scientist!
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Happy Birthday, Alistair W. G. Cameron

Born on June 21, 1925 in Canada, he was one of the founding fathers of the field of Nuclear Astrophysics.

Completely independently of other researchers, he developed pioneering ideas and models for understanding the origin of the cosmic elements from which most of our current ideas concerning element formation followed. Most of these ideas were summarized in 1957 scientific article which appeared in parallel to, but completely independently from, a similar article by Burbidge, Burbidge, Fowler and Hoyle, a more widely known research group at that time.

Originally trained as a nuclear physicist, he made major contributions in a number of fields, including nuclear reactions in stars, nucleosynthesis, the abundances of the elements in the Solar System, and the origin of the Solar System and the Moon. Also particularly noteworthy is his explanation of the formation of the Moon caused by a gigantic collision between a sub-planet and the young Earth. This is the currently accepted model for the origin of the Moon.

He was a remarkable person in many respects, as can be seen from his life told in these publications:
http://news.harvard.edu/gazette/story/2009/12/alastair-graham-walter-cameron/
http://www.nature.com/nature/journal/v438/n7069/full/438752a.html
And as also told by himself:
http://www.aip.org/history/ohilist/33763.html

(picture credit: http://pos.sissa.it/archive/conferences/028/205/NIC-IX_205.pdf )
#nucleosynthesis #moon 
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Studying the aftermath of a supernova explosion
 
Astronomers dissect the aftermath of a Supernova.

A team of astronomers has used radio telescopes in Australia and Chile to see inside the remains of a supernova. The supernova, known as SN1987A, was first seen by observers in the Southern Hemisphere in 1987 when a giant star suddenly exploded at the edge of a nearby dwarf galaxy called the Large Magellanic Cloud. Learn more: http://buff.ly/1AYnGd7
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The Cat's Eye Nebula - remains of a star

Seen with the Hubble Space Telescope, these expanding shells of gas are three thousand light-years away from Earth and about half a light year across. In the center of this nebula is a dying star, a sun-like star that has shrugged off its outer layers in several pulses, as seen by the concentric shells of gas moving outwards. The innermost structures seem to indicate more violent activity which currently is not well understood yet but may be due to a core He-flash, a violent phase of nuclear burning. In the end, a hot White Dwarf will be formed in the center that will just cool down while the ejected gas clouds keep expanding and cooling as well. The typical final fate of a low-mass star and our Sun will meet the same fate in 4.5 billion years.

Image Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA)
A different astronomy and space science related image is featured each day, along with a brief explanation.
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From the HAP website: The neutrino experiment Borexino  in the INFN  Gran Sasso Laboratories has managed to measure the energy of our star in real time: the energy released today at the centre of the Sun is exactly the same as that produced 100,000 years ago.

-- The Sun as Borexino Sees It in Real Time
http://www.hap-astroparticle.org/news.php#block405

#neutrinos #BOREXINO #Nature #astroparticle #HAPnews #whatyoumighthavemissedwhenIwasaway  
The neutrino experiment Borexino in the INFN Gran Sasso Laboratories has managed to measure the energy of our star in real time: the energy released today at the centre of the Sun is exactly the same as that produced 100000 years ago. For the first time in the history of scientific investigation ...
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If this doesn't fascinate you,  I don't know what will.
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Research news and other info mainly related to nucleosynthesis and nuclear astrophysics.