It holds the solar system together; provides life-giving light, heat, and energy to Earth; and generates space weather. The sun resides some 26, light-years from the Milky Way's center, in a tendril of our home galaxy known as the Orion Arm.
Every million years, the sun—and the solar system it carries with it—makes one orbit around the Milky Way's center. Though we can't feel it, the sun traces its orbit at an average velocity of , miles an hour. The sun formed more than 4. As it did, the cloud spun and flattened into a disk, with our sun forming at its center.
The disk's outskirts later accreted into our solar system, including Earth and the other planets. Scientists have even managed to see these planet-birthing disks around our sun's distant young cousins. Our home star is a yellow dwarf, a medium-size variety that's fairly common in our galaxy. On Earth, the sun can take on warmer hues, especially at sunrise or sunset, because our planet's atmosphere scatters blue and green light the most.
At about , miles 1. If it was a hollow ball, more than a million Earths could fit inside it. But the sun isn't hollow: It's filled with scorching gases and soups of electrically charged particles called plasma. The sun's surface temperature is about 10, degrees Fahrenheit 5, degrees Celsius , and it's 27 million degrees Fahrenheit Deep in the sun's core, nuclear fusion converts hydrogen to helium, which generates energy.
Particles of light called photons carry this energy through a spherical shell called the radiative zone to the top layer of the solar interior, the convection zone. There, hot plasmas rise and fall like the ooze in a lava lamp, which transfers energy to the sun's surface, called the photosphere. It can take , years for a photon to complete its journey out of the sun, but once it exits, it zips through space at more than , miles a second.
Solar photons reach Earth about eight minutes after they're freed from the sun's interior, crossing an average of 93 million miles to get here—a distance defined as one astronomical unit AU. There are billions more stars in the Milky Way galaxy - the galaxy we call home.
And there are many, many more in the rest of the universe. Is our Sun special? It turns out that our Sun is an average sized star. There are bigger stars, and there are smaller stars. We have found stars that are times bigger in diameter than our sun. Truly, those stars are enormous. We have also seen stars that are just one tenth the size of our sun. Many scientists think the sun and the rest of the solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula.
As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun. Related: How was the sun formed? The sun has enough nuclear fuel to stay much as it is now for another 5 billion years. After that, it will swell to become a red giant. Eventually, it will shed its outer layers, and the remaining core will collapse to become a white dwarf. Slowly, the white dwarf will fade, and will enter its final phase as a dim, cool theoretical object sometimes known as a black dwarf.
Related: When will the sun die? The sun and the atmosphere of the sun are divided into several zones and layers. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone.
The solar atmosphere above that consists of the photosphere, chromosphere, a transition region and the corona. Beyond that is the solar wind , an outflow of gas from the corona. The core extends from the sun's center to about a quarter of the way to its surface. Light from the core gets scattered in this zone, so that a single photon often may take a million years to pass through. Roiling "convection cells" of gas dominate this zone. Two main kinds of solar convection cells exist — granulation cells about miles 1, kilometers wide and supergranulation cells about 20, miles 30, km in diameter.
The photosphere is the lowest layer of the sun's atmosphere, and emits the light we see. Earth makes a complete orbit around the sun a year in Earth time in about days.
Earth is a rocky planet with a solid and dynamic surface of mountains, canyons, plains and more. Most of our planet is covered in water. Earth's atmosphere is 78 percent nitrogen, 21 percent oxygen and 1 percent other ingredients—the perfect balance to breathe and live.
Many orbiting spacecraft study the Earth from above as a whole system—observing the atmosphere, ocean, glaciers, and the solid earth.
Our atmosphere protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface. Storytellers explore the nature of our planet and possible alternate realities in many books, movies, and television shows. The iconic film "Planet of the Apes" and its sequels takes place in a future in which astronauts "discover" a planet inhabited by highly intelligent apes and primitive humans, only to realize later, much to their dismay, that — spoiler alert!
In the long-running and re-booted television series "Battlestar Galactica" — tired survivors of a war with highly evolved robots called Cylons are on a quest to find Earth, a long-lost colony. In other stories, Earth has been abandoned or destroyed, such as in the Joss Whedon series "Firefly," or the book and its film adaptation "The Hitchhiker's Guide to the Galaxy.
Our home planet Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains and so much more.
0コメント