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Related Concept Videos

Nuclear Stability03:18

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
Nuclear Fission02:50

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large number of different...
Nuclear Fusion02:45

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
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Nuclear Transmutation03:20

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Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
Atomic Nuclei: Nuclear Spin State Population Distribution01:14

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Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
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Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown
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Supernova 2007bi as a pair-instability explosion.

A Gal-Yam1, P Mazzali, E O Ofek

  • 1Benoziyo Center for Astrophysics, Faculty of Physics, The Weizmann Institute of Science, Rehovot 76100, Israel. avishay.gal-yam@weizmann.ac.il

Nature
|December 4, 2009
PubMed
Summary
This summary is machine-generated.

Extremely massive stars can explode as pair-instability supernovae. Observations of supernova SN 2007bi confirm this, revealing a massive star core and synthesized radioactive nickel.

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Area of Science:

  • Astronomy and Astrophysics
  • Stellar Evolution
  • Supernova Physics

Background:

  • Massive stars (10-100 solar masses) end as iron-core-collapse supernovae.
  • Extremely massive stars (>140 solar masses) may undergo pair-instability supernovae due to electron-positron pair production.
  • Transitional stars (100-140 solar masses) may exhibit characteristics of both supernova types.

Purpose of the Study:

  • To investigate the nature of supernova SN 2007bi, a luminous and slowly evolving object.
  • To test theoretical predictions of pair-instability supernovae.
  • To explore the existence of extremely massive stars in dwarf galaxies.

Main Methods:

  • Observational astronomy focusing on supernova SN 2007bi.
  • Estimation of the exploding core mass.
  • Analysis of synthesized radioactive nickel-56.
  • Comparison with theoretical models of pair-instability supernovae.

Main Results:

  • Supernova SN 2007bi had an estimated exploding core mass of approximately 100 solar masses.
  • Over 3 solar masses of radioactive nickel-56 were synthesized during the explosion.
  • Observations are consistent with models of pair-instability supernovae.

Conclusions:

  • SN 2007bi provides strong evidence for pair-instability supernovae.
  • Dwarf galaxies may host extremely massive stars, potentially exceeding the galactic stellar mass limit.
  • These massive stars could be analogous to the first stars formed in the universe.