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Sun : (1) the luminous celestial body around which the earth and other planets revolve, from which they receive heat and light, which is composed mainly of hydrogen and helium, and which has a mean distance from earth of about 93,000,000 miles (150,000,000 kilometers), a linear diameter of 864,000 miles (1,390,000 kilometers), and a mass 332,000 times greater than earth (2) a celestial body like the Sun — Webster
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 109 times that of Earth, and its mass is about 330,000 times that of Earth, accounting for about 99.86% of the total mass of the Solar System. About three quarters of the Sun’s mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.
The Sun is a G-type main-sequence star (G2V) based on its spectral class. As such, it is informally referred to as a yellow dwarf. It formed approximately 4.6 billion years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. It is thought that almost all stars form by this process.
The Sun is roughly middle-aged; it has not changed dramatically for more than four billion years, and will remain fairly stable for more than another five billion years. After hydrogen fusion in its core has diminished to the point at which it is no longer in hydrostatic equilibrium, the core of the Sun will experience a marked increase in density and temperature while its outer layers expand to eventually become a red giant. It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus, and render Earth uninhabitable. — Wikipedia
Heliophysics means “physics of the Sun” (the prefix “helio”, from Attic Greek hḗlios, means Sun), and appears to have been used only in that sense until quite recently. In the early times, heliophysics was concerned principally with the superficial layers of the star, and was synonymous with what is now more commonly called “solar physics”. Usage was extended explicitly in 1981 to its literal meaning, denoting the physics of the entire Sun: from center to corona, and has been used in that sense since. — Wikipedia
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Sun News -- ScienceDaily News about the Sun. Science articles on Sunspots and the Sun's Corona; evidence the Sun has a companion star; images from the far side of the Sun and more.
- Breakthrough in understanding cosmic forces that...on December 3, 2021 at 8:14 pm
Astrophysicists have made a breakthrough discovery in our understanding of the cosmic forces that shape the heliosphere.
- Closest pair of supermassive black holes yeton November 30, 2021 at 1:43 pm
Astronomers have revealed the closest pair of supermassive black holes to Earth ever observed. The two objects also have a much smaller separation than any other previously spotted pair of supermassive black holes and will eventually merge into one giant black hole.
- Largest comet ever observed was active at...on November 29, 2021 at 10:28 pm
Astronomers show that comet Bernardinelli-Bernstein (BB), the largest comet ever discovered, was active long before previously thought, meaning the ice within it is vaporizing and forming an envelope of dust and vapor known as a coma. Only one active comet has been observed farther from the sun, and it was much smaller than comet BB.
- Strong winds power electric fields in the upper...on November 29, 2021 at 10:27 pm
Using observations from NASA's ICON mission, scientists presented the first direct measurements of Earth's long-theorized dynamo on the edge of space: a wind-driven electrical generator that spans the globe 60-plus miles above our heads. The dynamo churns in the ionosphere, the electrically charged boundary between Earth and space. It's powered by tidal winds in the upper atmosphere that are faster than most hurricanes and rise from the lower atmosphere, creating an electrical environment that […]
- Sun is likely an unaccounted source of the...on November 29, 2021 at 5:27 pm
Curtin University researchers have helped unravel the enduring mystery of the origins of the Earth's water, finding the Sun to be a surprising likely source.
Solar Flare News -- ScienceDaily Latest research news on solar flares, the solar cycle, geomagnetic storms and more.
- A lab in the sky: Physics experiment in Earth’s...on October 27, 2021 at 4:20 pm
The Earth's atmosphere has been used as a 'laboratory' to carry out a physics experiment which could help to improve the performance of GPS.
- Radio signals from distant stars suggest hidden...on October 11, 2021 at 3:08 pm
Using the world's most powerful radio antenna, scientists have discovered stars unexpectedly blasting out radio waves, possibly indicating the existence of hidden planets.
- This is what it looks like when a black hole...on September 27, 2021 at 2:26 pm
Analyzing observations of an X-ray flare and fitting the data with theoretical models, astronomers documented a fatal encounter between an unlucky star and a black hole.
- Risk from solar flares to planes is real but not...on September 2, 2021 at 4:50 pm
Aviation guidelines aim to mitigate the effects of radiation, mainly caused by galactic cosmic rays and solar energetic particles, or SEP. The fluxes in the former are stable and predictable: dose rates are no higher than 10 µSv/h at the normal flight altitude of 12 km. But in the case of SEP, does the frequency of detected solar flares justify the costs of countermeasures? Current mitigation procedures instruct planes to lower altitude or change or cancel flight paths altogether, […]
- Will it be safe for humans to fly to Mars?on August 26, 2021 at 3:17 pm
A human space mission would be viable if it doesn't exceed four years, an international research team concludes in new research.
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Here are links to pages about closely related subjects.
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid