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Plutonium-244
Plutonium-244 (244Pu) is an isotope of plutonium that has a half-life of 80 million years. This is longer than any of the other isotopes of plutonium and longer than any other actinide isotope except for the three naturally abundant ones: uranium-235 (704 million years), uranium-238 (4.468 billion years), and thorium-232 (14.05 billion years). Although studies are in conflict, given the mathematics of the decay of plutonium-244, an exceedingly small amount should still be present in the Earth's composition, making plutonium a likely although unproven candidate as the shortest lived primordial element. Natural occurrence Accurate measurements, beginning in the early 1970s, have detected primordial plutonium-244, making it the shortest-lived primordial nuclide. The amount of 244Pu in the pre-Solar nebula (4.57×109 years ago) was estimated as 0.8% the amount of 238U. As the age of the Earth is about 57 half-lives of 244Pu, the amount of plutonium-244 left should be very small; ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plutonium
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous. Plutonium was first synthetically produced and isolated in late 1940 and early 1941, by a deuteron bombardment of uranium-238 in the cyclotron at the University of California, Berkeley. First, neptunium-238 ( half-life 2.1 days) was synthesized, which subsequently beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotopes Of Plutonium
Plutonium (94Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being 238Pu in 1940. Twenty plutonium radioisotopes have been characterized. The most stable are plutonium-244 with a half-life of 80.8 million years, plutonium-242 with a half-life of 373,300 years, and plutonium-239 with a half-life of 24,110 years. All of the remaining radioactive isotopes have half-lives that are less than 7,000 years. This element also has eight meta states; all have half-lives of less than one second. The isotopes of plutonium range in atomic weight from 228.0387 u (228Pu) to 247.074 u (247Pu). The primary decay modes before the most stable isotope, 244Pu, are spontaneous fission and alpha emission; the primary mode after is beta emission. The pri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primordial Isotope
In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the interstellar medium from which the solar system was formed, and were formed in, or after, the Big Bang, by nucleosynthesis in stars and supernovae followed by mass ejection, by cosmic ray spallation, and potentially from other processes. They are the stable nuclides plus the long-lived fraction of radionuclides surviving in the primordial solar nebula through planet accretion until the present; 286 such nuclides are known. Stability All of the known 251 stable nuclides, plus another 35 nuclides that have half-lives long enough to have survived from the formation of the Earth, occur as primordial nuclides. These 35 primordial radionuclides represent isotopes of 28 separate elements. Cadmium, tellurium, xenon, neodymium, samarium, osmium, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primordial Nuclide
In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the interstellar medium from which the solar system was formed, and were formed in, or after, the Big Bang, by nucleosynthesis in stars and supernovae followed by mass ejection, by cosmic ray spallation, and potentially from other processes. They are the stable nuclides plus the long-lived fraction of radionuclides surviving in the primordial solar nebula through planet accretion until the present; 286 such nuclides are known. Stability All of the known 251 stable nuclides, plus another 35 nuclides that have half-lives long enough to have survived from the formation of the Earth, occur as primordial nuclides. These 35 primordial radionuclides represent isotopes of 28 separate elements. Cadmium, tellurium, xenon, neodymium, samarium, osmium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primordial Nuclide
In geochemistry, geophysics and nuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed. Primordial nuclides were present in the interstellar medium from which the solar system was formed, and were formed in, or after, the Big Bang, by nucleosynthesis in stars and supernovae followed by mass ejection, by cosmic ray spallation, and potentially from other processes. They are the stable nuclides plus the long-lived fraction of radionuclides surviving in the primordial solar nebula through planet accretion until the present; 286 such nuclides are known. Stability All of the known 251 stable nuclides, plus another 35 nuclides that have half-lives long enough to have survived from the formation of the Earth, occur as primordial nuclides. These 35 primordial radionuclides represent isotopes of 28 separate elements. Cadmium, tellurium, xenon, neodymium, samarium, osmium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Star Merger
A neutron star merger is a type of stellar collision. It occurs in a fashion similar to the rare brand of type Ia supernovae resulting from merging white dwarf stars. When two neutron stars orbit each other closely, they gradually spiral inward due to gravitational radiation. When the two neutron stars meet, their merger leads to the formation of either a more massive neutron star, or a black hole (depending on whether the mass of the remnant exceeds the Tolman–Oppenheimer–Volkoff limit). The merger can also create a magnetic field that is trillions of times stronger than that of Earth in a matter of one or two milliseconds. These events are believed to create short gamma-ray bursts. The merger of binary neutron stars is believed to be the origin of most elements with large atomic weights - the r-process elements. The mergers are also believed to produce kilonovae, which are transient sources of fairly isotropic longer wave electromagnetic radiation due to the radio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
R-process
In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron, the "heavy elements", with the other half produced by the p-process and ''s''-process. The ''r''-process usually synthesizes the most neutron-rich stable isotopes of each heavy element. The ''r''-process can typically synthesize the heaviest four isotopes of every heavy element, and the two heaviest isotopes, which are referred to as ''r-only nuclei'', can be created via the ''r''-process only. Abundance peaks for the ''r''-process occur near mass numbers (elements Se, Br, and Kr), (elements Te, I, and Xe) and (elements Os, Ir, and Pt). The ''r''-process entails a succession of ''rapid'' neutron captures (hence the name) by one or more heavy seed nuclei, typically beginning with nuclei in the abundance peak centered on 56Fe. The captures must be rapid in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Nucleosynthesis
Stellar nucleosynthesis is the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original creation of hydrogen, helium and lithium during the Big Bang. As a predictive theory, it yields accurate estimates of the observed abundances of the elements. It explains why the observed abundances of elements change over time and why some elements and their isotopes are much more abundant than others. The theory was initially proposed by Fred Hoyle in 1946, who later refined it in 1954. Further advances were made, especially to nucleosynthesis by neutron capture of the elements heavier than iron, by Margaret and Geoffrey Burbidge, William Alfred Fowler and Hoyle in their famous 1957 B2FH paper, which became one of the most heavily cited papers in astrophysics history. Stars evolve because of changes in their composition (the abundance of their constituent elements) over their lifespans, first by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supernovae
A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion. The original object, called the ''progenitor'', either collapses to a neutron star or black hole, or is completely destroyed. The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. Supernovae are more energetic than novae. In Latin, ''nova'' means "new", referring astronomically to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word ''supernova'' was coined by Walter Baade and Fritz Zwicky in 1929. The last supernova to be directly observed in the Milky Way was Kepler's Supernova in 1604, appearing not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trace Radioisotope
A trace radioisotope is a radioisotope that occurs naturally in trace amounts (i.e. extremely small). Generally speaking, trace radioisotopes have half-lives that are short in comparison with the age of the Earth, since primordial nuclides tend to occur in larger than trace amounts. Trace radioisotopes are therefore present only because they are continually produced on Earth by natural processes. Natural processes which produce trace radioisotopes include cosmic ray bombardment of stable nuclides, ordinary alpha and beta decay of the long-lived heavy nuclides, thorium-232, uranium-238, and uranium-235, spontaneous fission of uranium-238, and nuclear transmutation reactions induced by natural radioactivity, such as the production of plutonium-239 and uranium-236 from neutron capture by natural uranium. Elements The elements that occur on Earth only in traces are listed below. Isotopes of other elements (not exhaustive): *Tritium * Beryllium-7 *Beryllium-10 *Carbon-14 *Fluorin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Samarium-146
Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm (half life: 1.06 y) and 148Sm (7 y), with 152Sm being the most abundant (26.75% natural abundance). 146Sm is also fairly long-lived (), but is not long-lived enough to have survived in significant quantities from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System as an extinct radionuclide. Other than the naturally occurring isotopes, the longest-lived radioisotopes are 151Sm, which has a half-life of 88.8 years, and 145Sm, which has a half-life of 340 days. All of the remaining radioisotopes, which range from 129Sm to 168Sm, have half-lives that are less than two days, and the majority of these have half-lives that are less than 48 seconds. This element also has twelve known nuclear isomer, isomers with the most stable being 141mSm (t1/2 22.6 minutes), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Capture
Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, which are repelled electrostatically. Neutron capture plays a significant role in the cosmic nucleosynthesis of heavy elements. In stars it can proceed in two ways: as a rapid process (r-process) or a slow process (s-process). Nuclei of masses greater than 56 cannot be formed by thermonuclear reactions (i.e., by nuclear fusion) but can be formed by neutron capture. Neutron capture on protons yields a line at 2.223 MeV predicted and commonly observed in solar flares. Neutron capture at small neutron flux At small neutron flux, as in a nuclear reactor, a single neutron is captured by a nucleus. For example, when natural gold (197Au) is irradiated by neutrons (n), the isotope 198Au is formed in a highly excited state, and quickly deca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
