Here"s a look at our solar system, from the scorching surface of Venus to the trang chủ of the largest volcano.
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In this illustration, the eight major planets of the solar system are shown orbiting the sun.(Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images)
The solar system is a collection of planets, moons, asteroids, comets, dust and gas that orbit our local star, the sun. It includes the rocky inner planets Mercury, Venus, Earth và Mars; the gas giants dòng jupiter and Saturn; and the ice giants Uranus & Neptune.
Between Mars and dòng jupiter is a collection of asteroids known as the asteroid belt, while beyond Neptune is where small icy bodies, like Pluto và comets, live.
How old is our solar system?
About 4.6 billion years ago, a giant cloud of dust and gas known as the solar nebula collapsed in on itself và began to form what would eventually become the solar system"s sun & planets. Meteorites, or pieces of space rock that have fallen to Earth, have helped scientists figure out the age of the solar system. Some of these small pieces have broken off of moons or planets và can yield interesting scientific information about the chemistry and history of their trang chủ body. Others have been traveling around the solar system since its beginning, before the planets even existed. The Allende meteorite, which fell khổng lồ Earth in 1969 & scattered over Mexico, is the oldest known meteorite, at 4.55 billion years old.
How did our solar system form?
Scientists think the solar system formed when a nearby exploding star, called a supernova, triggered the collapse of the solar nebula. According khổng lồ this theory, the explosion sent shock waves through space, & those shock waves pushed parts of the nebula closer together, leading lớn collapse. The supernova may have even seeded material into the nebula, Live Science previously reported. For instance, scientists have found that aluminum-26, an element formed only in the hearts of stars, most likely originated from a series of nearby supernovas, Live Science sister site Space.com reported (opens in new tab).
An image of a massive solar flare (or coronal mass ejection) erupting out of the sun in 2017. (Image credit: NASA) (opens in new tab)
The sun is at the center of the solar system và is its largest object, accounting for approximately 99.8% of the solar system"s mass, according lớn the University of California, San Diego (opens in new tab). The sun is a giant, raging ball of fire powered by nuclear reactions, & it provides the energy that sustains life on Earth. The yellow dwarf star is made up of gas — about 91% hydrogen & 8.9% helium, according to lớn NASA. Compared with other stars, the sun is relatively small và just one of hundreds of billions of stars in our home galaxy, the Milky Way.
The sun is about 26,000 light-years from the center of our galaxy, according lớn NASA (opens in new tab). The Milky Way is a spiral galaxy, with curved arms of stars emanating from its center. The solar system is located in one of the smaller arms, called the Orion-Cygnus Arm, or simply the Orion Arm.
The Milky Way is huge compared with the solar system. If the solar system were the kích cỡ of your hand, the Milky Way would be as big as North America, according to NASA Jet Propulsion Laboratory"s Night Sky Network (opens in new tab).
Our solar system"s planets
Eight confirmed planets và many dwarf planets (opens in new tab) orbit the sun. According khổng lồ NASA (opens in new tab), "the order & arrangement of the planets and other bodies in our solar system is due to lớn the way the solar system formed." Rocky materials could withstand the young sun"s immense heat, so the first four planets — Mercury, Venus, Earth & Mars — are small, with rocky surfaces. Beyond them, "materials we are used to seeing as ice, liquid or gas settled in the outer regions of the young solar system," NASA says, namely the gas giants đời yamaha jupiter and Saturn và the ice giants Uranus & Neptune.
Mercury transits the sun on Nov. 11, 2019. (Image credit: NASA/SDO/HMI/AIA) (opens in new tab)
Mercury (opens in new tab) is the closest planet lớn the sun. It is also the smallest planet in the solar system; at about 3,032 miles (4,879 kilometers) in diameter, it is only slightly larger than Earth"s moon & has no moons of its own. Mercury has no atmosphere khổng lồ protect it from the sun"s relentless radiation, & surface temperatures can reach highs of 800 degrees Fahrenheit (427 degrees Celsius) during the day & plummet as low as minus 290 F (minus 179 C) at night. Because of its speedy rotation around the sun, Mercury was named after the Roman messenger of the gods.
A NASA illustration shows the Pioneer-13 probes descending toward the clouds of Venus. (Image credit: NASA) (opens in new tab)
Named after the Roman goddess of love, Venus (opens in new tab) is the second planet from the sun and the hottest planet in the solar system. Its atmosphere is a thick layer of mostly carbon dioxide gas that traps heat, allowing the planet"s surface temperatures lớn reach a scorching 880 F (471 C). At 7,520 miles (12,100 km) in diameter, according lớn NASA (opens in new tab), Venus is slightly smaller than Earth and, lượt thích our planet, has a bộ vi xử lý core of molten iron.
In 2020, astronomers announced that they"d discovered phosphine in the atmosphere of Venus. On our planet, this chemical is almost always made by living creatures, leading some researchers khổng lồ wonder if Venus" clouds might host life. However, the findings are controversial & have yet to lớn be fully confirmed; indeed, other work has suggested that it would be too difficult for any creatures to lớn survive in such a hellish place because of the lack of much liquid water.
This image shows how sunlight fell on Earth during the winter solstice on Dec. 21, 2010. (Image credit: NASA) (opens in new tab)
The third rock from the sun, Earth is the only planet in the universe known khổng lồ harbor life. Its habitability is linked khổng lồ the presence of liquid water. Earth is located in the so-called Goldilocks zone, meaning it orbits at the ideal distance from the sun lớn have liquid water; if it were any closer, the water would evaporate into a gas, & if Earth were farther away, the water would freeze. About 71% of our planet"s surface is covered in water, according to the U.S. Geological Survey (opens in new tab), & Earth"s atmosphere protects the planet from solar radiation.
Earth is the only planet not named after a god. Earth likely earned its name from the English and German words for "ground." The blue planet is the largest of the four rocky planets in the solar system, and it has one moon. Scientists think Earth"s moon was formed from a piece of Earth that broke off when a giant object smashed into the young planet.
(Image credit: NASA/JPL-Caltech) (opens in new tab)
Mars (opens in new tab) is known as the Red Planet because of the iron-rich dust that covers its surface và gives it a rusty color. This red hue led the ancient Romans lớn name Mars after their god of war.
Mars, the fourth planet from the sun, is trang chủ to the largest volcano in the solar system, Olympus Mons (opens in new tab). The planet has a thin atmosphere, & without a thick protective shield, temperatures on Mars average around minus 80 F (minus 60 C).
It is likely that liquid water — which would provide a home for life as we know it — existed on the Martian surface billions of years ago, và some scientists think Mars may still have liquid water on its surface today. Mars has two moons: Phobos, which may have formed from ancient rings around the planet, & Deimos, which may have been knocked into its current orbit by an ancient, no-longer-existing moon.
This NASA Hubble Space Telescope image shows auroras above the poles of Jupiter. (Image credit: NASA, ESA, and J. Nichols (University of Leicester)) (opens in new tab)
Jupiter (opens in new tab) is the biggest planet in the solar system. Unlike the inner planets, dòng yamaha jupiter is a gas giant, made up mainly of helium and hydrogen. It is named after the king of the Roman gods (also known as Zeus in the Greek pantheon).
Jupiter, the fifth planet from the sun, is twice as big as all of the other planets in the solar system combined, yet it also has the shortest day of any planet, taking 10 hours lớn turn about its axis, according to lớn NASA (opens in new tab). đời xe jupiter is surrounded by dozens of moons, & its rings are faint và composed of dust. Deep in the planet"s atmosphere, high pressure & high temperatures have compressed the hydrogen gas into a liquid, creating the largest ocean in the solar system, according khổng lồ NASA.
(Image credit: NASA) (opens in new tab)
Saturn (opens in new tab), the sixth planet from the sun, is the second-largest planet in the solar system. Saturn is best known for its prominent rings. Lượt thích Jupiter, Saturn is a gas giant composed of helium và hydrogen, & it is the least dense of the planets. Saturn"s rings are made of billions of ice particles và rocks. The ringed planet also has dozens of moons, ranging in form size from that of a sports field lớn the kích thước of Mercury, according lớn NASA (opens in new tab). One of Saturn"s moons, Enceladus (opens in new tab), is covered in an icy ocean that astronomers say makes this moon a promising candidate for extraterrestrial life.
(Image credit: NASA/CXO/University College London/W. Dunn et al) (opens in new tab)
Uranus, the seventh planet from the sun, was the first planet khổng lồ be discovered using a telescope, by British astronomer William Herschel in 1781. The ice giant is composed of heavier elements than its gas giant neighbors — a mixture of water, methane và ammonia ice.
Unlike other planets in the solar system, Uranus effectively orbits on its side (with its axis almost pointing toward the sun), & it "rolls" lượt thích a ball as it travels around the sun. Methane gas in Uranus" atmosphere makes the planet appear green-blue. The planet has 13 rings & 27 moons. It is the only planet to lớn be named after a Greek deity, Ouranos the sky god, rather than a Roman one.
Neptune (opens in new tab), the eighth planet from the sun, was discovered in 1846. However, even before observing the planet for the first time, scientists predicted its existence, because of its effect on Uranus" orbit.
Neptune, which is named after the Roman sea god, is so far from the sun that it takes 4.15 hours for sunlight lớn reach the planet, according to Cornell University (opens in new tab). (For comparison, it takes about eight minutes (opens in new tab) for sunlight khổng lồ reach Earth.) When the light arrives at Neptune, it is 900 times dimmer than what we see on Earth, according to lớn NASA (opens in new tab).
Neptune is made up of water, methane và ammonia surrounding a small, rocky core. Strong winds on the planet propel clouds of frozen methane at speeds of up to lớn 1,200 mph (2,000 km/h). Neptune has 14 known moons, one of which was rediscovered after going missing (opens in new tab) for đôi mươi years.
Why is Pluto not a planet?
NASA’s New Horizons spacecraft took this enhanced color image of Pluto on July 14, 2015. (Image credit: NASA/JHUAPL/SwRI) (opens in new tab)
Pluto, once considered the ninth planet in the solar system, was reclassified as a dwarf planet in 2006 (opens in new tab) because it failed to meet one of the criteria in the definition of a planet. The International Astronomical Union (opens in new tab) defines a planet as a celestial body that orbits the sun, has enough gravity lớn pull itself into a round or almost-round shape, và has cleared the neighborhood around its orbit. Pluto has not cleared the neighborhood around its orbit, so it"s not considered a planet.
Some astronomers believe this reclassification is unfair (opens in new tab) and that Pluto should be reinstated as the ninth planet in the solar system. Looking at the historical literature, Philip Metzger, a planetary scientist at the University of Central Florida, found that before the 2006 decision the "clearing the neighborhood" rule appeared only in a single 1801 paper. He và his colleagues concluded that this Pluto-excluding rule is "arbitrary and not based on historical precedent," Live Science previously reported, và that therefore Pluto should still be considered a planet.
Pluto, which is named after the Roman god of the underworld, sits in the vast Kuiper Belt, a region beyond Neptune that contains trillions of icy objects.
An illustration shows what Planet 9 might look like orbiting far from our sun. (Image credit: NASA) (opens in new tab)
There is a possible candidate to fill Pluto"s vacancy as the ninth planet: Planet X, or Planet Nine. In a 2016 paper published (opens in new tab)in The Astronomical Journal, California Institute of giải pháp công nghệ astronomers Mike Brown and Konstantin Batygin hypothesized that a planet 10 times larger than Earth could be orbiting the sun about 20 times farther away than Neptune does.
"All those people who are mad that Pluto is no longer a planet can be thrilled to lớn know that there is a real planet out there still khổng lồ be found," Brown said at the time (opens in new tab). "Now, we can go and find this planet và make the solar system have nine planets once again."
However, Planet Nine"s existence is still theoretical, because the planet has not been directly observed, according khổng lồ NASA (opens in new tab).
Between the planets
Between Mars & Jupiter, there is a huge collection of asteroids known as the main asteroid belt. These space rocks are leftovers from the formation of the solar system, & there are over a million known asteroids all over the solar system, according to NASA.
Asteroids come in a wide variety of types và are classified based on their composition.
Beyond the planets
Artist"s impression of Kuiper Belt objects. (Image credit: MARK GARLICK/SCIENCE PHOTO LIBRARY via Getty Images) (opens in new tab)
Beyond the ice giant Neptune, the solar system extends khổng lồ the Kuiper Belt & the Oort cloud. The Kuiper Belt (opens in new tab), whose existence was confirmed in 1992, is 30 to lớn 55 astronomical units (AU) wide, according khổng lồ NASA (opens in new tab). (One AU is the average distance between Earth & the sun — about 93 million miles, or 150 million km.)
The Kuiper Belt"s most famous inhabitant is Pluto, but the region also contains hundreds of thousands of frozen objects 62 miles (100 km) or larger in diameter, many of which are remnants of the early solar system, according khổng lồ NASA (opens in new tab).
The Oort cloud (opens in new tab), which is a collection of comets different than the Kuiper belt because it is located far, far in the solar system"s icy outer reaches, has been hypothesized since the 1950s, but it has never been observed.
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Adam Mann is a freelance journalist with over a decade of experience, specializing in astronomy & physics stories. He has a bachelor"s degree in astrophysics from UC Berkeley. His work has appeared in the New Yorker, thành phố new york Times, National Geographic, Wall Street Journal, Wired, Nature, Science, and many other places. He lives in Oakland, California, where he enjoys riding his bike.