Spotting an exoplanet around a faraway star is like spotting a firefly next to a lighthouse. The light from the lighthouse is so bright that you would have a hard time spotting the flicker of a firefly. In the same way, all stars are bigger and staggeringly bright compared to the planets orbiting them.
So far, the planets outside our solar system have proven to be fascinating and diverse. The force of gravity there would be much stronger than here at home. You would weigh twice as much there as you do on Earth! Another planet, called Keplerb, turns out to orbit two stars. A sunset there would provide a view of two setting stars!
Most of the material was pulled toward the center to form the sun. Other particles within the disk collided and stuck together to form asteroid-sized objects named as planetesimals, some of which combined to become the asteroids, comets , moons and planets.
The solar wind from the sun was so powerful that it swept away most of the lighter elements, such as hydrogen and helium, from the innermost planets, leaving behind mostly small, rocky worlds.
The solar wind was much weaker in the outer regions, however, resulting in gas giants made up mostly of hydrogen and helium.
The sun is by far the largest object in our solar system, containing It sheds most of the heat and light that makes life possible on Earth and possibly elsewhere. Planets orbit the sun in oval-shaped paths called ellipses, with the sun slightly off-center of each ellipse. NASA has a fleet of spacecraft observing the sun, such as the Parker Solar Probe , to learn more about its composition, and to make better predictions about solar activity and its effect on Earth.
The four inner four planets — Mercury, Venus, Earth and Mars — are made up mostly of iron and rock. They are known as terrestrial or earth-like planets because of their similar size and composition.
Earth has one natural satellite — the moon — and Mars has two moons — Deimos and Phobos. Between Mars and Jupiter lies the Asteroid Belt. Asteroids are minor planets, and scientists estimate there are more than , of them with diameters larger than three-fifths of a mile 1 km and millions of smaller asteroids. The dwarf planet Ceres , about miles km in diameter, resides here. A number of asteroids have orbits that take them closer into the solar system that sometimes lead them to collide with Earth or the other inner planets.
This is how the idea of Martians came into being, and in English author H. Wells published his science fiction novel The War of the Worlds about a Martian invasion. Jupiter , the largest planet in our solar system, is one of the brightest objects in the night sky and held great importance to everyone from the Ancient Chinese to the Greeks. In , Galileo was the first person to make detailed observations of the planet and notice its four largest moons; Io, Europa, Ganymede and Callisto.
As the last classical planet, Saturn has been known since antiquity with its first written record dating back to the Assyrians around BCE. Detailed observations of the planet became possible with the invention of telescopes, and in Galileo saw its rings for the first time, although he mistakenly believed them to be moons.
Uranus can be seen with the naked eye, but is difficult to spot due to its dimness and the fact it takes Our planetary system is named the "solar system" because our Sun is named Sol, after the Latin word for Sun, "solis," and anything related to the Sun we call "solar. Our solar system extends much farther than the eight planets that orbit the Sun.
The solar system also includes the Kuiper Belt that lies past Neptune's orbit. This is a sparsely occupied ring of icy bodies, almost all smaller than the most popular Kuiper Belt Object — dwarf planet Pluto. Beyond the fringes of the Kuiper Belt is the Oort Cloud. This giant spherical shell surrounds our solar system. It has never been directly observed, but its existence is predicted based on mathematical models and observations of comets that likely originate there.
The Oort Cloud is made of icy pieces of space debris - some bigger than mountains — orbiting our Sun as far as 1. This shell of material is thick, extending from 5, astronomical units to , astronomical units. One astronomical unit or AU is the distance from the Sun to Earth, or about 93 million miles million kilometers. The Oort Cloud is the boundary of the Sun's gravitational influence, where orbiting objects can turn around and return closer to our Sun. The Sun's heliosphere doesn't extend quite as far.
The heliosphere is the bubble created by the solar wind — a stream of electrically charged gas blowing outward from the Sun in all directions. The boundary where the solar wind is abruptly slowed by pressure from interstellar gases is called the termination shock.
This edge occurs between astronomical units. Voyager 1 went interstellar in and Voyager 2 joined it in But it will be many thousands of years before the two Voyagers exit the Oort Cloud. There are more than known moons in our solar system and several more awaiting confirmation of discovery.
0コメント