The sun rotates counterclockwise, and takes between 25 and 35 days to complete a single rotation. The sun orbits clockwise around the center of the Milky Way. Its orbit is between 24, and 26, light-years away from the galactic center. The sun takes about million to million years to orbit one time around the galactic center.
The electromagnetic spectrum exists as waves of different frequencies and wavelengths. The frequency of a wave represents how many times the wave repeats itself in a certain unit of time. Waves with very short wavelengths repeat themselves several times in a given unit of time, so they are high-frequency.
In contrast, low-frequency waves have much longer wavelengths. The vast majority of electromagnetic waves that come from the sun are invisible to us.
The most high-frequency waves emitted by the sun are gamma rays, X-rays, and ultraviolet radiation UV rays. Less potent UV rays travel through the atmosphere, and can cause sunburn. The sun also emits infrared radiation —whose waves are a much lower-frequency. Most heat from the sun arrives as infrared energy. Sandwiched between infrared and UV is the visible spectrum, which contains all the colors we, as humans, can see.
The color red has the longest wavelengths closest to infrared , and violet closest to UV the shortest. The sun itself is white, which means it contains all the colors in the visible spectrum.
The sun appears orangish-yellow because the blue light it emits has a shorter wavelength , and is scattered in the atmosphere—the same process that makes the sky appear blue.
Evolution of the Sun The sun, although it has sustained all life on our planet, will not shine forever. The sun has already existed for about 4. Through nuclear fusion, the sun is constantly using up the hydrogen in its core :Every second, the sun fuses around million metric tons of hydrogen into helium.
Over the next five billion years, the sun will burn through most of its hydrogen, and helium will become its major source of fuel. The outer layers of the sun will expand from this extra energy. The sun will expand to about times its current radius, swallowing Mercury and Venus. As the sun expands, it will spread its energy over a larger surface area, which has an overall cooling effect on the star. When it reaches this temperature, helium will begin fusing to create carbon, a much heavier element.
This will cause intense solar wind and other solar activity, which will eventually throw off the entire outer layers of the sun. The red giant phase will be over. Temperatures in the core exceed The core is the only place where nuclear fusion reactions can happen.
Protons of hydrogen atoms violently collide and fuse, or join together, to create a helium atom. This process, known as a PP proton-proton chain reaction, emits an enormous amount of energy. The energy released during one second of solar fusion is far greater than that released in the explosion of hundreds of thousands of hydrogen bombs. During nuclear fusion in the core, two types of energy are released: photons and neutrinos.
These particles carry and emit the light, heat, and energy of the sun. Photons are the smallest particle of light and other forms of electromagnetic radiation. The sun emits both photons and neutrinos in all directions, all the time. Radiative Zone The radiative zone of the sun starts at about 25 percent of the radius, and extends to about 70 percent of the radius.
In this broad zone, heat from the core cools dramatically, from between seven million K to two million K. In the radiative zone, energy is transferred by a process called thermal radiation.
During this process, photons that were released in the core travel a short distance, are absorbed by a nearby ion, released by that ion, and absorbed again by another. One photon can continue this process for almost , years! Transition Zone : Tachocline Between the radiative zone and the next layer, the convective zone, there is a transition zone called the tachocline.
Differential rotation happens when different parts of an object rotate at different velocities. The sun is made up of gases undergoing different processes at different layers and different latitudes. The rotation rate of the sun changes rapidly in the tachocline. Instead, it transfers heat by thermal convection through thermal columns.
When the gases reach the outer limits of the convective zone, they cool down, and plunge back to the base of the convective zone, to be heated again. Photosphere The photosphere is the bright yellow, visible "surface" of the sun. Scientists can study these gasses to see how the magnetic lines of force are oriented in space, the same way you use iron filings to study the magnetic field of a toy magnet in class.
Prominences are like pencils balanced on their point. They can appear motionless for hours, then suddenly erupt, spewing out their trapped gases into space. As you ride the solar convection you find yourself swimming around with sunspots and other odd things. Suddenly, like some enormous earthquake, the gases around you start to move violently. Everything around you begins to move away from the Sun in a huge cloud of hot gas!
Watch a Solar Surface Movie. Look at an Enlarged Picture Storms: You are part of a huge cloud of gas that starts out over 10 times bigger than the entire Earth.
It grows bigger and bigger as it moves away from the Sun. The bubble will travel through space at nearly a million miles an hour. The cloud you are riding is shaped like a gigantic gas bubble that is hollow inside.
We are lucky, here on Earth, that very few of these gigantic storm clouds are shot towards the Earth. In , scientist William Hyde Wollaston noticed that sunlight passing through a prism produced the expected rainbow spectrum, but with notable dark lines scattered here and there. To get a better look at this phenomena, optician Joseph von Fraunhofer, invented the first spectrometer — basically an improved prism — that spread the different wavelengths of sunlight out even more, making them easier to see.
It also made it easier to see that Wollaston's dark lines weren't a trick or illusion — they seemed to be a feature of sunlight. Scientists figured out that those dark lines now called Fraunhofer lines corresponded to the specific wavelengths of light absorbed by certain elements like hydrogen, calcium and sodium.
Therefore, those elements must be present in the outer layers of the sun, absorbing some of the light being emitted by the core. Over time, increasingly sophisticated detection methods have allowed us to quantify the output from the sun: electromagnetic radiation in all its forms X-rays, radio waves, ultraviolet, infrared and so on and the flow of subatomic particles like neutrinos.
By measuring what the sun releases and what it absorbs, we've built a very thorough understanding of the sun's composition from afar. Did you happen to notice any patterns in the materials that make up the sun? Hydrogen and helium are the first two elements on the periodic table: the simplest and lightest.
The heavier and more complex an element, the less of it we find in the sun. In the immediate aftermath of the Big Bang, the universe was nothing more than a hot, dense cloud of subatomic particles. For a long time, the universe was dominated by hydrogen and helium atoms that were able to form spontaneously within the primordial subatomic soup. Slowly, these atoms begin to form loose aggregations. These aggregations exerted greater gravity, so they kept growing, pulling in more material from nearby.
After about 1. Coronagraph: This image of the Sun was taken March 2, The smaller inner circle is where the Sun would be if it were visible in this image. The corona extends millions of kilometers above the photosphere and emits about half as much light as the full moon.
Just as bright city lights make it difficult to see faint starlight, so too does the intense light from the photosphere hide the faint light from the corona. While the best time to see the corona from Earth is during a total solar eclipse, it can be observed easily from orbiting spacecraft. Studies of its spectrum show the corona to be very low in density. The corona thins out very rapidly at greater heights, where it corresponds to a high vacuum by Earth laboratory standards.
These particles flow outward from the Sun into the solar system at a speed of about kilometers per second almost 1 million miles per hour! The solar wind exists because the gases in the corona are so hot and moving so rapidly that they cannot be held back by solar gravity. This wind was actually discovered by its effects on the charged tails of comets; in a sense, we can see the comet tails blow in the solar breeze the way wind socks at an airport or curtains in an open window flutter on Earth.
Although the solar wind material is very, very rarified i. Astronomers estimate that the Sun is losing about 10 million tons of material each year through this wind. While this amount of lost mass seems large by Earth standards, it is completely insignificant for the Sun. Figure From where in the Sun does the solar wind emerge? In visible photographs, the solar corona appears fairly uniform and smooth.
X-ray and extreme ultraviolet pictures, however, show that the corona has loops, plumes, and both bright and dark regions. Large dark regions of the corona that are relatively cool and quiet are called coronal holes Figure In these regions, magnetic field lines stretch far out into space away from the Sun, rather than looping back to the surface. The solar wind comes predominantly from coronal holes, where gas can stream away from the Sun into space unhindered by magnetic fields.
Hot coronal gas, on the other hand, is present mainly where magnetic fields have trapped and concentrated it. However, the magnetic field lines come into Earth at the north and south magnetic poles. Here, charged particles accelerated by the solar wind can follow the field down into our atmosphere. As the particles strike molecules of air, they cause them to glow, producing beautiful curtains of light called the auroras , or the northern and southern lights Figure The stunning display captured here occurred over Jokulsarlon Lake in Iceland in The Sun, our star, has several layers beneath the visible surface: the core, radiative zone, and convective zone.
These, in turn, are surrounded by a number of layers that make up the solar atmosphere. In order of increasing distance from the center of the Sun, they are the photosphere, with a temperature that ranges from K to about K; the chromosphere, with a typical temperature of 10 4 K; the transition region, a zone that may be only a few kilometers thick, where the temperature increases rapidly from 10 4 K to 10 6 K; and the corona, with temperatures of a few million K.
Solar wind particles stream out into the solar system through coronal holes. Skip to main content. Search for:. Key Concepts and Summary The Sun, our star, has several layers beneath the visible surface: the core, radiative zone, and convective zone. Licenses and Attributions. CC licensed content, Shared previously. Gravitational acceleration at photosphere surface gravity.
0コメント