9/5/2023 0 Comments Sizewise aplWe also have included the radii sizes relative to Earth to help you picture them better. “A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.” Size of the Eight Planets:Īccording to NASA, this is the estimated radii of the eight planets in our solar system, in order of size. This is the current IAU planet definition: The result was redefining Pluto and worlds like it as a dwarf planet. Stern (SwRI), and the HST Pluto Companion Search Team Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. At first astronomers began treating these new worlds like planets, but as more information came in, the International Astronomical Union held a meeting to better figure out the definition. The other change was finding worlds similar to Pluto, then considered the Solar System’s furthest planet, far out in our own Solar System. This began with finding massive planets many times larger than Jupiter, and then eventually finding planets that are rocky - even a few that are close to Earth’s size itself. Scientists discovered exoplanets, or planets that are outside of our solar system. As telescope technology improved, however, two things happened. Until the 1990s, scientists only knew of planets in our own Solar System and at that point accepted there were nine planets. Since much of the gas ended up in the outer parts of the system, this may explain why there are gas giants - although this presumption may not be true for other solar systems discovered in the universe. That led to the birth of Earth and the other eight planets in our Solar System. As larger balls of matter formed, they swept the smaller particles away and eventually cleared their orbits. Over millions and millions of years, the gas and dust particles became attracted to each other by their mutual gravities and began to combine or crash. Artist’s conception of a solar system in formation. Some theories say that the young Sun’s energy began pushing the lighter particles of gas away, while larger, more solid particles such as dust remained closer in. Gravitational attraction at its center eventually collapsed to form the Sun. Today, scientists believe the Solar System began with a spinning gas and dust cloud. As more information comes in, some of our theories of the Solar System must change to suit the new evidence. No human was around 4.5 billion years ago when the Solar System was formed, so what we know about its birth comes from several sources: examining rocks on Earth and other places, looking at other solar systems in formation and doing computer models, among other methods. This article explores the planets in order of size, with a bit of context as to how they got that way. While humans think of Earth as a large planet, in reality it is dwarfed by the massive gas giants lurking at the outer edges of our Solar System. What also is amazing is the sheer size difference of planets. If you’re interested in planets, the good news is there’s plenty of variety to choose from in our own Solar System. From the ringed beauty of Saturn, to the massive hulk of Jupiter, to the lead-melting temperatures on Venus, each planet in our solar system is unique - with its own environment and own story to tell about the history of our Solar System.
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