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The Sun photographed at a wavelength of 19.3 nanometers (ultraviolet) Despite its name, the heliosphere's shape is not a perfect sphere. [6] Its shape is determined by three factors: the interstellar medium (ISM), the solar wind, and the overall motion of the Sun and heliosphere as it passes through the ISM.
Helium is the least water-soluble monatomic gas, [96] and one of the least water-soluble of any gas (CF 4, SF 6, and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 −5, respectively, versus helium's 0.70797 x 2 /10 −5), [97] and helium's index of refraction is closer to unity than that of any other gas. [98]
The Fraunhofer lines are typical spectral absorption lines. Absorption lines are narrow regions of decreased intensity in a spectrum, which are the result of photons being absorbed as light passes from the source to the detector. In the Sun, Fraunhofer lines are a result of gas in the Sun's atmosphere and outer photosphere. These regions have ...
Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen. Rockets need to achieve specific speeds and ...
The Sun is a typical star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere. Astronomers classify it as a G-type main-sequence star. The largest objects that orbit the Sun are the eight planets.
Helium 3 is rare on Earth, primarily produced by the radioactive decay of tritium, but it does reside in abundance in the lunar regolith, deposited by billions of years of solar wind.
Sun passes through helium-burning horizontal-branch and asymptotic-giant-branch phases, losing a total of ~30% of its mass in all post-main-sequence phases. The asymptotic-giant-branch phase ends with the ejection of its outer layers as a planetary nebula , leaving the dense core of the Sun behind as a white dwarf .
That’s where helium comes in: With a boiling point of minus 452 degrees Fahrenheit, liquid helium is the coldest element on Earth. Pumped inside an MRI magnet, helium lets the current travel ...