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Nuclear Astrophysics
2,277 followers -
scientific research in astrophysics and basic nuclear science
scientific research in astrophysics and basic nuclear science

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today, all over the world: 641 satellite marches!

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today!

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A New Blast May Have Forged Cosmic Gold
For decades, researchers believed that violent supernovas forged gold and other heavy elements. But many now argue for a different cosmic quarry.

Good introductory article on the current status of nucleosynthesis research regarding heavy elements.

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nice picture of an expanding cloud stemming from a supernova explosion
Sharpless 249 and the Jellyfish Nebula
Image Credit & Copyright: Eric Coles
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic mosaic. The scene is anchored below by bright star Eta Geminorum, at the foot of the celestial twin, while the Jellyfish Nebula is the brighter arcing ridge of emission with tentacles dangling below and left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper right. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this narrowband composite image presented in the Hubble Palette would be about 300 light-years across.

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Manipulative Spam Emails from Internal Medicine Review

Every scientist and researcher should be warned about these! Read the article (and look at my "personal" sample below). And adjust the spam filters of your e-mail as well as of your brain.

In a way, I was happy to read that I am not the only one wondering about this spam. It is spam but on a more sophisticated level. But not sophisticated enough that I did not find it weird to be asked to publish a follow up on an astrophysics article in a medical journal. But had I been in medical research indeed, I couldn't have helped to give it some consideration.

Here is the latest one I just received (even personalized with "Happy New Year"), lots of those went directly into the spam folder within the past year(s):

"Dear Dr. Rauscher,
 
I wish you a happy new year. We talked some months ago about the idea of publishing a followup article to the one you authored entitled "Solution of the ?-potential mystery in the ? process and its impact on the Nd/Sm ratio in meteorites". Is now a better time for you to write something? Is there anything I can do to help? If now isn't the right time for you to work on a followup to this article, I would certainly be interested in knowing more about your current research.

I will tell you more about the journal in case you don't still have our earlier emails. The Internal Medicine Review is a hybrid journal with optional open access. The issues are monthly, and published both online and in print. The submission deadline is flexible.

Please get back to me at your earliest convenience.

 
Sincerely,
 
Dr. Lisseth Tovar
Senior Editor
Internal Medicine Review (IMR)
www.internalmedicinereview.org "

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As every year, today we celebrate the birthday of one of the founding fathers of the field of Nuclear Astrophysics.

The experimental nuclear physicist received the Nobel prize in physics in 1983 "for his theoretical and experimental studies of the nuclear reactions of importance in the formation of the chemical elements in the universe".
Happy Birthday, Willy!

One of the founding fathers of the field of Nuclear Astrophysics, he was born August 9th, 1911, in Pittsburgh, Pennsylvania. He received the Nobel Prize for Physics in 1983 for his theoretical and experimental studies of the nuclear reactions of importance in the formation of the chemical elements in the universe.

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Long-delayed nuclear center looks set for construction

After many years of delays, the €1.7 billion Facility for Antiproton and Ion Research, an extension of the GSI Helmholtz Center for Heavy Ion Research near Darmstadt, Germany, may finally get built. At a council meeting on 27 and 28 June, the partner countries—eight European Union members plus India and Russia—concluded that they have enough money to cover a €320 million budget gap; they will now seek building permits from the German government. Still, some countries have yet to commit their share of the missing cash, including Russia, which had agreed to bear about 18% of FAIR's total construction cost, the second largest contribution after Germany's 70%.

If construction proceeds now and goes as planned, first experiments can start as soon as 2022 and FAIR would be completed in 2025. This may still be optimistic, though.

One of the science directions at FAIR will be the study of matter at conditions found in the early universe and in stellar explosions.

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Shapes and decays of nuclei tell us about symmetries in the universe
From Atoms To Everything

An atom is comprised of dense nucleus of protons and neutrons surrounded by a diffuse cloud of electrons. Since an atomic nucleus is held together by the strong force, similar to the way gravity holds stars and planets together, you would think nuclei would be basically spherical. This isn’t always the case, and a few such as barium-144 are even pear shaped. This has to do with a subtle way the Universe works, which could explain one of its biggest mysteries.

As Emmy Noether demonstrated in the early 1900s, symmetry is connected to the basic laws of physics. The presence of certain symmetries in the world is a property of certain unchanging quantity in the Universe. Noether’s theorem is an elegant demonstration of this connection, and is central to most modern physical theories. Noether showed us how some of the most powerful symmetries are those connected to space and time.

Take, for example, mirror symmetry, also known as parity. When you look in a mirror, the image you see is reversed. If you hold up your right hand, your mirror image would seem to hold up its left. Mirror image clocks would appear to move counter clockwise. So imagine a mirror universe. Not the evil Spock kind of mirror universe, but simply one in which the parity of everything is reversed. Americans would drive on the left side of the road, the Sun would rise in the west and set in the East, but fundamentally nothing would change. It would be no different than if we simply decided to switch the meanings of right and left.

At least that would be the case if parity symmetry were true. While usually things are symmetrical under a switch of parity, there are some cases were parity is violated. This was first demonstrated by the Wu experiment in 1956. Chien-Shiung Wu looked at the radioactive decay of cobalt-60 atoms. If parity was conserved, then mirror image decay experiments should behave in exactly the same way. What she found was that mirrored experiments of cobalt-60 decayed in opposite directions. Since radioactive decay is driven by the weak nuclear force, this meant the weak force violates parity.

Another symmetry is related to electromagnetic charge. In our Universe protons have a positive charge while electrons have a negative charge. Charge symmetry considers what would happen if these charges were reversed. Since antimatter particles have the opposite charge of their regular matter partners, this would be like replacing all matter with antimatter. Since positive charges interact with each other the same way as negative charges, you would think that charge symmetry would hold. After all, it’s why charge is conserved.

But it turns out charge symmetry can be violated in a subtle way, again connected to the weak interaction, specifically neutrinos. While neutrinos don’t have any charge, they do have a kind of rotation known as helicity. If charge symmetry were true, then matter and antimatter should produce neutrinos with the same helicity. But it turns out matter produces neutrinos of one helicity, while antimatter produces antineutrinos of the opposite helicity. So charge symmetry is violated as well. For a time it was thought that the symmetries of charge and parity could be combined into a more general CP symmetry that would be conserved, but there are radioactive particles that violate it as well.

So what does any of this have to do with pear-shaped atomic nuclei? The shape of a nucleus is determined by the various interactions that occur between the protons and neutrons (and quarks) within the nucleus. If those interactions were CP symmetric, there shouldn’t be a pear-shaped nucleus like barium-144. By studying odd nuclei like barium-144, we can gain clues about the ways CP-symmetry can be violated.

What does this have to do with astrophysics? Remember that charge symmetry is connected to matter and antimatter. Because charge is conserved, when any particle of matter is produced through some physical process, a corresponding particle of antimatter must also be produced. In the early moments after the big bang, when matter was being produced for the first time, there should have been an equal amount of matter and antimatter. But what we see today is a Universe dominated by matter. The origin of this matter-antimatter asymmetry is one of the great unanswered questions of cosmology. It’s been proposed that a violation of CP symmetry could have produced more matter than antimatter, but the currently known violations are not sufficient to produce the amount of matter we see. If there are other avenues of CP violation hidden within pear-shaped nuclei, they could explain this mystery after all.

Paper: C. S. Wu, et al. Experimental Test of Parity Conservation in Beta Decay. Physical Review 105 (4): 1413–1415. (1957)

Paper: B. Bucher et al. Direct Evidence of Octupole Deformation in Neutron-Rich 144Ba. Phys. Rev. Lett. 116, 112503 (2016) arXiv:1602.01485 [nucl-ex]

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