Follow me around our solar system - The Sun

2020-05-31 23:01



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The Sun, our star, the heart of our solar system is a yellow dwarf star, a hot ball of glowing gases.


Overview


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The Sun is a yellow dwarf star, a hot ball of glowing gases at the heart of our solar system. Its gravity holds the solar system together, keeping everything from the biggest planets to the smallest particles of debris in its orbit.

The connection and interactions between the Sun and Earth drive the seasons, ocean currents, weather, climate, radiation belts and auroras. Though it is special to us, there are billions of stars like our Sun scattered across the Milky Way galaxy.

The Sun has many names in many cultures. The Latin word for Sun is “sol,” which is the main adjective for all things Sun-related: solar.


Myths about Sun


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The Sun's Closest Neighbors


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the Alpha Centauri triple star system: Proxima Centauri is 4.24 light years away, and Alpha Centauri A and B, two stars orbiting each other, are 4.37 light years away.


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This NASA/ESA Hubble Space Telescope has given us this stunning view of the bright Alpha Centauri A (on the left) and Alpha Centauri B (on the right)




Orbit and Rotation


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The Sun, and everything that orbits it, is located in the Milky Way galaxy.


Our Sun is in a spiral arm called the Orion Spur that extends outward from the Sagittarius arm. From there, the Sun orbits the center of the Milky Way Galaxy, bringing the planets, asteroids, comets and other objects along with it.


Our solar system is moving with an average velocity of 720,000 kilometers per hour.


But even at this speed, it takes us about 230 million years to make one complete orbit around the Milky Way.



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Structure


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The Sun's enormous mass is held together by gravitational attraction, producing immense pressure and temperature at its core. The Sun has six regions: the core, the radiative zone, and the convective zone in the interior; the visible surface, called the photosphere; the chromosphere; and the outermost region, the corona.


At the core, the temperature is about 15 million degrees Celsius), which is sufficient to sustain thermonuclear fusion. This is a process in which atoms combine to form larger atoms and in the process release staggering amounts of energy. Specifically, in the Sun’s core, hydrogen atoms fuse to make helium.


The energy produced in the core powers the Sun and produces all the heat and light the Sun emits. Energy from the core is carried outward by radiation, which bounces around the radiative zone, taking about 170,000 years to get from the core to the top of the convective zone.


The temperature drops below 2 million degrees Celsius in the convective zone, where large bubbles of hot plasma (a soup of ionized atoms) move upwards.


The surface of the Sun, the part we can see, is about 5,500 degrees Celsius. That's much cooler than the blazing core, but it's still hot enough to make carbon, like diamonds and graphite, not just melt, but boil.


What Color is the Sun?


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It is a common misconception that the Sun is yellow, or orange or even red. However, the Sun is essentially all colors mixed together, which appear to our eyes as white. This is easy to see in pictures taken from space.


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Acturally, the Sun is all colors of The Rainbow. Each color in the rainbow (red, orange, yellow, green, blue, violet) has a different wavelength. Red is the longest, blue the shortest.


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Actually, all forms of light and energy are part of the same phenomena: the electromagnetic spectrum. Our eyes can detect only a small amount of this energy, that portion we call "visible light." Radio waves, X-rays, microwaves, gamma rays, and the rest all have longer or shorter wavelengths than visible light, but otherwise are the same phenomena.


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Surface


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The surface of the Sun, the photosphere, is a 500 kilometer thick region, from which most of the Sun's radiation escapes outward.


This is not a solid surface like the surfaces of planets. Instead, this is the outer layer of the gassy star.


We see radiation from the photosphere as sunlight when it reaches Earth about eight minutes after it leaves the Sun.

The temperature of the photosphere is about 5,500 degrees Celsius.


Atmosphere


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Above the photosphere lie the tenuous chromosphere and the corona (crown), which make up the thin solar atmosphere. This is where we see features such as sunspots and solar flares.


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SUNSPOT


Visible light from these top regions is usually too weak to be seen against the brighter photosphere, but during total solar eclipses, when the moon covers the photosphere, the chromosphere looks like a red rim around the Sun, while the corona forms a beautiful white crown with plasma streamers narrowing outward, forming shapes that look like flower petals.



Magnetosphere


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The electric currents in the Sun generate a complex magnetic field that extends out into space to form the interplanetary magnetic field. The volume of space controlled by the Sun's magnetic field is called the heliosphere.


The Sun's magnetic field is carried out through the solar system by the solar wind—a stream of electrically charged gas blowing outward from the Sun in all directions. Since the Sun rotates, the magnetic field spins out into a large rotating spiral, known as the Parker spiral.


The Sun doesn't behave the same way all the time. It goes through phases of its own solar cycle. Approximately every 11 years, the Sun's geographic poles change their magnetic polarity. When this happens, the Sun's photosphere, chromosphere and corona undergo changes from quiet and calm to violently active. The height of the Sun's activity, known as solar maximum, is a time of solar storms: sunspots, solar flares and coronal mass ejections. These are caused by irregularities in the Sun's magnetic field and can release huge amounts of energy and particles, some of which reach us here on Earth. This space weather can damage satellites, corrode pipelines and affect power grids.


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The Sun releases a constant stream of particles and magnetic fields called the solar wind. This solar wind slams worlds across the solar system with particles and radiation, which can stream all the way to planetary surfaces unless thwarted by an atmosphere, magnetic field, or both. Here's how these solar particles interact with a few select planets and other celestial bodies. Credit: NASA's Goddard Space Flight Center/Mary Pat Hrybyk-Keith


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The next we will unlock The Kuiper Belt。


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