 Hydrogen |
| Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. Stars in
the main sequence are mainly composed of hydrogen in its plasma state. Molecular clouds of H2 are associated with star formation.
Hydrogen plays a vital role in powering stars through proton-proton reaction and CNO cycle nuclear fusion.
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| Throughout the universe, hydrogen is mostly found in the atomic and plasma states whose properties are quite different from
molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical
conductivity and high emissivity (producing the light from the sun and other stars).
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| Helium |
| Helium is the second lightest element and is the second most abundant in the observable Universe. Most helium was formed during
the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen in stars.
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| Beryllium |
| Beryllium is a relatively rare element in both the Earth and the universe, because it is not formed in conventional stellar
nucleosynthesis.
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| Carbon |
| Carbon is the fourth most abundant chemical element in the universe by mass after hydrogen, helium, and oxygen. Carbon is
abundant in the Sun, stars, comets, and in the atmospheres of most planets. Some meteorites contain microscopic diamonds that
were formed when the solar system was still a protoplanetary disk. Microscopic diamonds may also be formed by the intense
pressure and high temperature at the sites of meteorite impacts.
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| Nitrogen |
| Molecular nitrogen and nitrogen compounds have been detected in interstellar space by astronomers using the Far Ultraviolet
Spectroscopic Explorer. Molecular nitrogen is a major constituent of the Saturnian moon Titan's thick atmosphere, and occurs
in trace amounts in other planetary atmospheres.
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| Oxygen |
| Oxygen is the third most abundant element in the universe by mass after hydrogen and helium. |
| About 0.9% of the Sun's mass is oxygen. Mars' atmosphere has an oxygen concentration of 0.1% O2 by volume, Earth's by contrast, is 21%.
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| Neon |
| Neon is actually abundant on a universal scale; it's the fifth most abundant chemical element in the universe by mass, after
hydrogen, helium, oxygen, and carbon.
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| Mass abundance in the universe is about 1 part in 750 and in the Sun and presumably in the proto-solar system nebula, about
1 part in 600.
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| The Galileo spacecraft atmospheric entry probe found that in the upper atmosphere of Jupiter, neon is found in a ratio of
1 part in 6000, by mass.
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| Sodium |
| Sodium is relatively abundant in stars and the D spectral lines of this element are among the most prominent in star light.
Though elemental sodium has a rather high vaporization temperature, its relatively high abundance and very intense spectral
lines have allowed its presence to be detected by ground telescopes and confirmed by spacecraft (Mariner 10 and MESSENGER)
in the thin atmosphere of the planet Mercury.
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| Magnesium |
| Magnesium is the ninth most abundant element in the universe by mass. |
| Aluminium |
| Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released
by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion
years ago.
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| Silicon |
| Silicon is a principal component of aerolites, which are a class of meteoroids, a small sand- to boulder-sized particle of
debris in the Solar System.
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| Sulphur |
| The distinctive colours of Jupiter's volcanic moon, Io, are from various forms of molten, solid and gaseous sulfur. There
is also a dark area near the Lunar crater Aristarchus that may be a sulfur deposit.
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| Sulfur is present in many types of meteorites. Ordinary chondrites contain on average 2.1% sulfur, and carbonaceous chondrites
may contain as much as 6.6%. Sulfur in meteorites is normally present entirely as troilite (FeS), but other sulfides are found
in some meteorites, and carbonaceous chondrites contain free sulfur, sulfates, and possibly other sulfur compounds.
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| Argon |
| The Martian atmosphere in contrast contains 1.6% of argon-40 and 5 ppm of argon-36. The Mariner spaceprobe fly-by of the planet
Mercury in 1973 found that Mercury has a very thin atmosphere with 70% argon, believed to result from releases of the gas
as a decay product from radioactive materials on the planet. In 2005, the Huygens probe also discovered the presence of argon-40
on Titan, the largest moon of Saturn.
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| Calcium |
| In the visible portion of the spectrum of many stars, including the Sun, strong absorption lines of singly-ionized calcium
are shown. Prominent among these are the H-line at 3968.5 Å and the K line at 3933.7 Å of singly-ionized calcium, or Ca II.
For the Sun and stars with low temperatures, the prominence of the H and K lines can be an indication of strong magnetic activity
in the chromosphere. Measurement of periodic variations of these active regions can also be used to deduce the rotation periods
of these stars.
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| Titanium |
| Titanium is contained in meteorites and has been detected in the sun and in M-type stars; the coolest type of star with a
surface temperature of 3,200°C (5,792°F). Rocks brought back from the moon during the Apollo 17 mission are composed of 12.1%
TiO2.
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| Iron |
| Iron is the heaviest element produced by stellar nucleosynthesis; heavier elements require a red giant or supernova for their
formation. Iron and nickel are the most abundant metals in iron meteorites and in the dense metal cores of planets such as
Earth. Although rare, meteorites are the major form of natural metallic iron on the Earth's surface.
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| In phases of the meteorites Semarkona and Chervony Kut a correlation between the concentration of 60Ni, the daughter product of 60Fe, and the abundance of the stable iron isotopes could be found which is evidence for the existence of 60Fe at the time of formation of the solar system. Possibly the energy released by the decay of 60Fe contributed, together with the energy released by decay of the radionuclide 26Al, to the remelting and differentiation of asteroids after their formation 4.6 billion years ago. The abundance of 60Ni present in extraterrestrial material may also provide further insight into the origin of the solar system and its early
history.
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| Nickel |
| Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in
supernova nucleosynthesis of elements heavier than iron.
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| Yttrium |
| Yttrium in the Solar System was created through stellar nucleosynthesis, mostly by the s-process (about 72%), but also by
the r-process (about 28%). The r-process consists of rapid neutron capture of lighter elements during supernova explosions.
The s-process is a slow neutron capture of lighter elements inside pulsating red giant stars.
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| Zirconium |
| Zirconium is relatively-abundant in S-type stars, and it has been detected in the sun and in meteorites. Lunar rock samples
brought back from several Apollo program missions to the moon have a quite high zirconium oxide content relative to terrestrial
rocks.
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| Technetium |
| No isotope of technetium has a half-life longer than 4.2 million years (98Tc), so its detection in red giants in 1952 helped bolster the theory that stars can produce heavier elements.
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| Xenon |
| Xenon is relatively rare in the Sun's atmosphere, on Earth, and in asteroids and comets. The atmosphere of Mars shows a xenon
abundance similar to that of Earth: 0.08 parts per million, however Mars shows a higher proportion of 129Xe than the Earth or the Sun.
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| The planet Jupiter has an unusually high abundance of xenon in its atmosphere; about 2.6 times as much as the Sun. |
| Unlike the lower mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Elements
more massive than iron-56 have a net energy cost to produce through fusion, so there is no energy gain for a star to create
xenon. Instead, many isotopes of xenon are formed during supernova explosions.
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| Promethium |
| Promethium has also been identified in the spectrum of the star HR 465 in Andromeda, and possibly HD 101065 (Przybylski's
star) and HD 965.
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| Europium |
| Europium has been identified in the spectra of the sun and certain stars. |
| Iridium |
| Iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more. The Willamette meteorite, the largest
meteorite found in the U.S., has 4.7 ppm iridium.
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| Platinum |
| Platinum exists in relatively higher abundances on the Moon and in meteorites. Correspondingly, platinum is found in slightly
higher abundances at sites of bolide impact on the Earth that are associated with resulting post-impact volcanism, and can
be mined economically; the Sudbury Basin is one such example.
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