Discover the Planets in Solar System: From Mercury to Neptune and Everything in Between
The order of the planets in the solar system, starting nearest the sun and working outward is the following: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and then the possible Planet Nine.
planets in solar system
The solar system extends from the sun, goes past the four inner planets, through the asteroid belt to the four gas giants and on to the disk-shaped Kuiper Belt and far beyond to the teardrop-shaped heliopause.
Scientists estimate that the edge of the solar system is about 9 billion miles (15 billion kilometers) from the sun. Beyond the heliopause lies the giant, spherical Oort Cloud, which is thought to surround the solar system.
Ever since the discovery of Pluto in 1930, kids grew up learning that the solar system has nine planets. That all changed in the late 1990s when astronomers started arguing about whether Pluto was indeed a planet. In a highly controversial decision, the International Astronomical Union ultimately decided in 2006 to designate Pluto as a "dwarf planet," reducing the list of the solar system's true planets to just eight.
Astronomers, however, are still hunting for another possible planet in our solar system, a true ninth planet, after mathematical evidence of its existence was revealed on Jan. 20, 2016. The alleged "Planet Nine," also called "Planet X," is believed to be about 10 times the mass of Earth and 5,000 times the mass of Pluto.
Jupiter and Saturn are sometimes called the gas giants, whereas the more distant Uranus and Neptune have been nicknamed the ice giants. This is because Uranus and Neptune have more atmospheric water and other ice-forming molecules, such as methane, hydrogen sulfide and phosphene, that crystallize into clouds in the planets' frigid conditions, according to the Planetary Society. For perspective, methane crystallizes at minus 296 Fahrenheit (minus 183 degrees Celsius), according to the U.S. National Library of Medicine.
How many planets are in our solar system?[^5^]
What is the order of the planets in our solar system?[^1^]
What are the names of the planets in our solar system?[^1^]
What are the characteristics of the planets in our solar system?[^2^]
What are the differences between terrestrial and giant planets in our solar system?[^2^]
How did the planets in our solar system form?[^3^]
How do the planets in our solar system orbit the Sun?[^2^]
What are the temperatures of the planets in our solar system?[^2^]
What are the sizes and masses of the planets in our solar system?[^2^]
What are the atmospheres of the planets in our solar system?[^2^]
How many moons do the planets in our solar system have?[^2^]
What are the rings of the planets in our solar system?[^2^]
What are the dwarf planets in our solar system?[^2^] [^3^]
How do we explore the planets in our solar system?[^4^]
What are some interesting facts about the planets in our solar system?[^4^]
How do the planets in our solar system affect each other?[^4^]
How do we compare the planets in our solar system to exoplanets?[^4^]
What are some challenges and opportunities for visiting the planets in our solar system?[^4^]
How do we protect the planets in our solar system from contamination?[^4^]
How do we measure the distances of the planets in our solar system?[^4^]
How do we classify the planets in our solar system?[^3^] [^5^]
How do we name the planets in our solar system and their features?[^3^] [^5^]
How do we observe and study the planets in our solar system?[^3^] [^5^]
How do we model and simulate the planets in our solar system?[^3^] [^5^]
How do we communicate with spacecraft exploring the planets in our solar system?[^3^] [^5^]
How do we determine the ages of the planets in our solar system?[^3^] [^5^]
How do we predict and track the motions of the planets in our solar system?[^3^] [^5^]
How do we understand and explain the origin and evolution of the planets in our solar system?[^3^] [^5^]
How do we search for life on other planets in our solar system?[^3^] [^5^]
How do we compare and contrast Earth with other planets in our solar system?[^3^] [^5^]
What are some myths and legends about the planets in our solar system?[^1^] [^3^] [^5
The sun is by far the largest object in our solar system, containing 99.8% of the solar system's mass. 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.
Venus is the second planet from the sun and is the hottest planet in the solar system. Its thick atmosphere is extremely toxic and composed of sulfuric acid clouds, the planet is an extreme example of the greenhouse effect.
The average temperature on Venus' surface is 900 F (465 C). At 92 bar, the pressure at the surface would crush and kill you. And oddly, Venus spins slowly from east to west, the opposite direction of most of the other planets.
Venus is sometimes referred to as Earth's twin as they are similar in size and radar images beneath its atmosphere reveal numerous mountains and volcanoes. But beyond that, the planets could not be more different.
Between Mars and Jupiter lies the asteroid belt. Asteroids are minor planets, and according to NASA there are approximately between 1.1 and 1.9 million asteroids in the main asteroid belt larger than 0.6 miles (1 km) in diameter and millions more smaller asteroids.
The dwarf planet Ceres, about 590 miles (950 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.
Neptune is the eighth planet from the sun and is on average the coldest planet in the solar system. The average temperature of Neptune at the top of the clouds is minus 346 degrees Fahrenheit (minus 210 degrees Celsius).
Scientists thought it might be nothing more than a hunk of rock on the outskirts of the solar system. But when NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015, it transformed scientists' view of Pluto.
Scientists have not seen Planet Nine. They inferred its existence by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy rocks left over from the birth of the solar system. Also called trans-Neptunian objects, these Kuiper Belt objects have highly elliptical or oval orbits that align in the same direction.
A hypothesis proposed in September 2019 on the pre-print server arXiv suggests Planet Nine might not be a planet at all. Instead, Jaku Scholtz of Durham University and James Unwin of the University of Illinois at Chicago speculate it could be a primordial black hole that formed soon after the Big Bang and that our solar system later captured, according to Newsweek. Unlike black holes that form from the collapse of giant stars, primordial black holes are thought to have formed from gravitational perturbations less than a second after the Big Bang, and this one would be so small (5 centimeters in diameter) that it would be challenging to detect.
Past the Kuiper Belt is the very edge of the solar system, the heliosphere, a vast, teardrop-shaped region of space containing electrically charged particles given off by the sun. Many astronomers think that the limit of the heliosphere, known as the heliopause, is about 9 billion miles (15 billion km) from the sun.
The sun accumulated about 99% of the available matter and the remaining material further from the sun formed smaller clumps inside the spinning disk. Some of these clumps gained enough mass that their gravity shaped them into spheres, becoming planets, dwarf planets and moons. Other leftover pieces became asteroids, comets and smaller moons that make up our solar system.
For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named them planets, meaning "wanderers." Mercury, Venus, Mars, Jupiter and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today.
Explore the solar system in greater detail with these interactive resources from NASA. Discover the wonders of the solar system with this educational material from ESA. See where the planets are in their current orbit of the sun with this interactive orrery from NASA.
Beyond Neptune, a newer class of smaller worlds called dwarf planets reign, including longtime favorite Pluto. Thousands more planets have been discovered beyond our solar system. Scientists call them exoplanets (exo means "from outside").
The key difference between a planet and a dwarf planet is the kinds of objects that share its orbit around the Sun. Pluto, for example, has not cleared its orbit of similar objects while Earth or Jupiter have no similarly-sized worlds on the same path around the Sun. Like planets, dwarf planets are generally round (Haumea looks like an overinflated football) and orbit the Sun.
This simulated view of our solar system at the top of this page (and below) runs on real data. The position of the planets, moons, and spacecraft are shown where they are right now. This digital orrery (a model of the solar system) runs on a light, mobile-mobile friendly version of NASA's Eyes on the Solar System software.
The Solar System[c] is the gravitationally bound system of the Sun and the objects that orbit it. The largest of such objects are the eight planets, in order from the Sun: four terrestrial planets named Mercury, Venus, Earth and Mars, two gas giants named Jupiter and Saturn, and two ice giants named Uranus and Neptune. The terrestrial planets have a definite surface and are mostly made of rock and metal. The gas giants are mostly made of hydrogen and helium, while the ice giants are mostly made of 'volatile' substances such as water, ammonia, and methane. In some texts, these terrestrial and giant planets are called the inner Solar System and outer Solar System planets respectively.
The Solar System was formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. Over time, the cloud formed the Sun and a protoplanetary disk that gradually coalesced to form planets and other objects. That is the reason why all eight planets have an orbit that lies near the same plane. In the present day, 99.86% of the Solar System's mass is in the Sun and most of the remaining mass is contained in the planet Jupiter. Six planets, six largest possible dwarf planets and many other bodies have natural satellites or moons orbiting around them. All giant planets and a few smaller bodies are encircled by planetary rings, composed of ice, dust and sometimes moonlets.
There are an unknown number of smaller dwarf planets and innumerable small bodies orbiting the Sun.[d] These objects are distributed in the asteroid belt that lies between the orbits of Mars and Jupiter, the Kuiper belt, the scattered disc that both lies beyond Neptune's orbit and at even further reaches of the Solar System which they would be classified as an extreme trans-Neptunian object. There is consensus among astronomers to these nine objects as dwarf planets: the asteroid Ceres, the Kuiper-belt objects Pluto, Orcus, Haumea, Quaoar, and Makemake, and the scattered-disc objects Gonggong, Eris, and Sedna.[d] Many small-body populations, including comets, centaurs and interplanetary dust clouds, freely travel between the regions of the Solar System.
The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region of the interplanetary medium in the interstellar medium known as the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium; it extends out to the edge of the scattered disc. The Oort cloud, which is thought to be the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere. The nearest stars to the Solar System are within the Local Bubble; the closest star is named Proxima Centauri and is at a distance of 4.2441 light-years away.