The solar system may be moving through space three times faster than expected. The location of the outer edge of the solar system is also a subject of debate among astronomers. Here’s a simple guide to the sizes and locations of the planets in our solar system.
The solar system may be moving through space three times faster than expected. Is the standard cosmological model wrong? If our solar system is indeed moving at this speed, we need to reconsider our fundamental assumptions about the large-scale structure of the universe.
Astronomers have discovered that the solar system may be moving through space more than three times faster than previously thought. This discovery could have implications for the standard model of cosmology, our current best explanation for the structure, composition, and evolution of the universe. The team’s research results were published on November 10, 2025, in the journal Physical Review Letters.
The team of researchers who conducted this study reached their conclusions using the LOFAR (Low Frequency Array) radio telescope network and two other radio telescopes to map the distribution of radio galaxies, which they then used to measure the motion of the Solar System. Radio galaxies are galaxies that emit unusually strong radio waves from “lobes” extending far beyond the visible structure of stars.
Radio galaxies are useful in this regard because radio waves have a long enough wavelength to penetrate cosmic gas and dust, rather than being absorbed as other forms of electromagnetic radiation are. A slightly higher number of radio galaxies should appear in the direction of the solar system’s motion, but this change is so small that it can only be detected with extremely sensitive instruments.
An illustration of our solar system (not to scale). buradaki/iStock/Getty Images Plus
“Our analysis shows that the solar system is moving more than three times faster than current models predict,” said team leader Lukas Böhme of Bielefeld University. “This result clearly contradicts expectations based on standard cosmology and forces us to reconsider our previous assumptions.”
The team’s measurements revealed a discrepancy in the distribution of radio galaxies, an anisotropy, that was 3.7 times stronger than predicted by the standard cosmological model that describes the evolution of the cosmos since the Big Bang.
These results are consistent with previous infrared observations of quasars powering supermassive black holes, which glow brightly due to the enormous amount of energy released by the surrounding matter. The correlation between these two separate lines of research suggests that this is not an error, but a reflection of a genuine cosmic feature.
“If our solar system is indeed moving at such a speed, we need to question fundamental assumptions about the large-scale structure of the universe,” said team member Dominik J. Schwarz, a cosmologist at Bielefeld University. “Alternatively, the distribution of radio galaxies itself may be less uniform than we thought. In any case, our current models are being tested.”
The location of the outer edge of the solar system is a subject of debate among astronomers. There are three possible candidates, “each worthy of consideration.” According to NASA, there are not one, but three potential boundaries of the solar system: the Kuiper Belt, a ring of rocky bodies beyond the orbit of Neptune; the heliopause, the edge of the sun’s magnetic field; and the Oort Cloud, a distant cluster of comets barely visible from Earth. Arguments for each boundary are “worthy of consideration,” making choosing between them difficult.
The solar system is a vast space. Our cosmic neighborhood contains eight planets, about half a dozen dwarf planets, several hundred moons, and millions of asteroids and comets, all orbiting the Sun—and in many cases, each other—at thousands of miles per hour, like a giant spinning top.
An artist’s rendering of the solar system. The solar system has three potential boundaries, depending on how you define it. Getty Images
According to NASA, the Kuiper Belt extends between 30 and 50 astronomical units (AU) from the Sun. (One AU is equal to the distance between Earth and the Sun.)
The region is full of asteroids and dwarf planets like Pluto, which were ejected from the inner solar system as a result of one-sided gravitational encounters with planets.
Some astronomers argue that the Kuiper Belt should be considered the edge of the solar system, as it roughly represents the edge of where the Sun’s protoplanetary disk—the rotating ring of gas and dust that later became the planets, moons, and asteroids—would have been.
“If we think of the solar system in a narrow sense as just the Sun and its planets, then the edge of the Kuiper Belt can be considered the edge of the solar system,” Reisenfeld said.
However, some astronomers, such as Mike Brown of the California Institute of Technology, consider this definition of the solar system too simplistic.
The Kuiper Belt is made up primarily of asteroids. Getty Images
“That’s not quite true,” Brown wrote in an email to Live Science. “A lot has changed since the planets formed—mostly, their distances have increased.” This means the Kuiper Belt doesn’t contain all of the solar system’s “contents,” such as the elusive hypothetical Planet Nine, which (if it exists) likely resides far beyond the Kuiper Belt.
In October 2023, the discovery of a dozen new objects beyond the Kuiper Belt also hinted that a “second Kuiper Belt” may be lurking even further out.
Therefore, the uncertainty about the outer boundary of this region makes it an unreliable boundary for the entire solar system as a whole, some researchers argue.
The heliopause is the outer boundary of the Sun’s magnetic influence, known as the heliosphere. At this point, the flow of charged particles emitted by the Sun, known as the solar wind, becomes too weak to repel the incoming flow of radiation from stars and other cosmic objects in the Milky Way.
“Because the plasma within the heliopause is of solar origin, and the plasma beyond the heliopause is of interstellar origin, some consider the heliopause to be the boundary of the solar system,” Reisenfeld said. As a result, the space beyond the heliopause is also often referred to as “interstellar space,” or the space between the stars, he added.
Two spacecraft have crossed the heliopause: Voyager 1, which made the journey in 2012, and Voyager 2, which crossed it in 2018. According to Brown, when the Voyager probes crossed the heliopause, they quickly detected changes in the types and levels of magnetism and radiation hitting them, indicating that they had crossed some kind of boundary.
The heliopause is the point where the solar wind meets interstellar space. NASA/JPL-Caltech
However, despite its name, the heliosphere is not a perfect sphere. Rather, it is an elongated mass, as most of the interstellar plasma bombarding the solar system hits us from one direction, creating a bow shock—a rounded shock wave that deflects incoming radiation across the rest of the solar system. The bow shock is located approximately 120 astronomical units from the sun and creates a long tail extending at least 350 astronomical units from the sun in the opposite direction.
Using the heliopause to define the boundaries of the solar system thus results in an asymmetric environment, which contradicts some researchers’ ideas about planetary systems.
According to NASA, the Oort Cloud is the most distant and extensive potential boundary of the Solar System, extending up to 100,000 astronomical units from the Sun.
“People who define the solar system as everything gravitationally bound to the sun consider the edge of the Oort cloud to be the edge of the solar system,” Reisenfeld said.
For some researchers, this is an obvious choice for the boundary of the solar system, since theoretically a planetary system consists of all objects orbiting a star.
“I don’t understand how anyone can consider anything other than the Oort Cloud to be the edge of the solar system,” Sean Raymond, an astronomer at the Bordeaux Astrophysics Laboratory in France, wrote in an email to Live Science. “Any other definition seems preposterous. It’s literally the edge where anything can orbit the Sun.”
The Oort Cloud (left) is much larger than the inner solar system (right) or the Kuiper Belt (center). Getty Images
However, other researchers believe that since the Oort cloud is located in interstellar space, it is located outside the Solar System, even if it is associated with our home star.
There is also great uncertainty about where exactly the Oort cloud ends, which some argue makes it as unreliable a boundary as the Kuiper Belt.
Of the three possible boundaries, the heliopause is the one most often used by researchers and NASA to define the edge of the solar system. This is because it is the easiest to accurately determine, and because the magnetic properties on either side of it differ significantly.
“I would say the heliopause is a boundary because it really is a boundary,” Reisenfeld said. “Once you cross it, you’ll feel it.”
But that doesn’t mean everything beyond the heliopause should be considered an interstellar object, such as the massive space rock ‘Oumuamua, Reisenfeld added. “The Oort Cloud was originally composed of the same material from which the planets formed, so it’s made of solar system material, not interstellar material,” he said.
But while some researchers are willing to take sides in this debate, others see no reason why the solar system cannot have multiple boundaries.
“I would say there’s no real debate here,” Brown said. “There are simply different ways to frame the issue depending on what’s important to answering the question.”
The outer solar system is a vast and mysterious place that may hide objects we know almost nothing about, from the elusive Planet Nine and young black holes to interstellar aliens and planet-destroying asteroids.
You might think we know the solar system pretty well, but there’s much more to our cosmic environment than meets the eye (or the eyeball).
Most interesting objects, such as planets, moons, and the asteroid belt, are relatively densely packed in the center of the solar system and illuminated by sunlight, making them fairly easy to spot. But if you look to the edge of the solar system, you’ll discover a vast, dark space that could easily harbor mysterious objects. As a result, researchers are eagerly speculating about all sorts of things that could be lurking there.
From a massive Planet Nine and a second Kuiper Belt to interstellar aliens and mini-black holes, here are eight hypothetical objects that could be lurking in the dark.
The largest and most controversial object that may be lurking in our cosmic neighborhood is a hypothetical ninth planet, located far beyond the other known worlds in our solar system, which researchers have ingeniously dubbed “Planet Nine.”
The largest and most controversial object that may be lurking in our cosmic neighborhood is a hypothetical ninth planet, located far beyond the other known worlds in our solar system, which researchers have ingeniously dubbed “Planet Nine.”
In 2016, scientists first proposed the existence of Planet Nine to explain the eccentric orbits of several large objects in and around the Kuiper Belt—the massive ring of asteroids and other rocky objects orbiting the Sun beyond Neptune. Some researchers believe these objects are gravitationally attracted by a massive, unknown world beyond the Kuiper Belt. However, despite the discovery of even more such objects in recent years, a true planet remains undetected.
If it exists, Planet Nine is likely an icy gas giant, approximately seven times more massive than Earth, making it the fifth-largest planet in the Solar System. However, the planet would be extremely distant, perhaps orbiting the Sun once every 10,000 years, meaning it would be very dim and extremely difficult to detect.
Researchers have narrowed down the area where Planet Nine might be hiding, but their ability is limited by the power of currently available telescopes.
Not everyone believes that Planet Nine is responsible for the orbital anomalies of Kuiper Belt objects. Other scientists believe that these distant space rocks may be gravitationally influenced by something equally elusive—a miniature black hole.
Researchers argue that a black hole roughly the size of the moon or a planet could exert a gravitational force similar to that of the proposed Planet Nine. Black holes of this size are theoretically possible, but have never been observed, making the idea somewhat controversial. To prove this theory, researchers would likely need to detect Hawking radiation emanating from the black hole or observe an object falling beyond its event horizon.
Miniature black holes could theoretically be lurking in our cosmic environment, unsuspected. NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)
But even if the young black hole isn’t masquerading as Planet Nine, other researchers believe that even smaller “primordial” black holes may exist in the outer solar system, and that these ultra-small singularities could be causing some planets and moons to wobble.
Some researchers believe that, in addition to Planet Nine, there may be other hidden worlds on the outskirts of the Solar System.
But unlike Planet Nine, these hypothetical planets—known as rogue planets—may not have originated locally. Instead, they may have been ejected objects from distant stars, likely drawn in by the Sun after drifting through interstellar space for many years.
Alien planets, captured by the gravity of our Sun, may be lurking in the shadows of the outer Solar System. Wikimedia Commons, reproduced under a Creative Commons BY-SA 4.0 license.
Scientists have already discovered hundreds of rogue planets hurtling through the Milky Way. However, in 2023, researchers suggested that another rogue planet may be lurking at the edge of the Solar System, even further than Planet Nine. And if that weren’t enough, a 2024 paper also suggested that there’s room for five Earth-sized rogue planets at the edge of space.
The Kuiper Belt may play a key role in discovering hidden worlds in the Solar System. But it may also harbor a secret of its own—its twin.
In 2023, researchers announced the potential discovery of a dozen new rocky objects lurking beyond the Kuiper Belt. These massive space rocks, likely asteroids, are located approximately 10 astronomical units (10 times the distance between Earth and the Sun) from the main Kuiper Belt, suggesting they may belong to a second, smaller asteroid belt.
However, other studies have not found any more such objects beyond the Kuiper Belt, leaving this theory in limbo for now.
After full-fledged worlds and missing asteroid belts, the next largest objects that could be lurking under our noses are dwarf planets—large space rocks large enough to be gravitationally taut like planets, but not large enough to completely clear their orbits of debris.
According to NASA, there are five known dwarf planets in the solar system: Ceres, Haumea, Eris, Makemake, and the former planet Pluto. Other candidates, such as Gongun, Quaoar, and Sedna, are not officially recognized as dwarf planets, but astronomers often refer to them as such.
Dozens of dwarf planets like Eris (pictured) may be waiting to be discovered. Shutterstock
All of these mini-worlds are located within or beyond the Kuiper Belt—with the exception of Ceres, which is located in the asteroid belt between Mars and Jupiter. But the outer Solar System contains numerous places where objects could be hiding. According to some estimates by the International Astronomical Union, dozens or even hundreds of dwarf planets may still be waiting to be discovered.
Until recently, researchers believed that dwarf planets were mostly geologically dead, with the exception of Pluto, which hosts an icy supervolcano. However, new data collected by the James Webb Space Telescope have revealed that Eris and Makemake may also be geologically active, raising the possibility that they or other future dwarf planets could harbor extraterrestrial life.
Far beyond the Kuiper Belt lies a gigantic cluster of comets known as the Oort Cloud, extending approximately 1,000 astronomical units from the Sun. A very small percentage of these icy objects are so-called cryovolcanoes, or cold volcanoes, which erupt, spewing dust and frozen gas into space.
Cryovolcanic comets erupt only near the Sun, when solar radiation causes intense pressure within their outer shells, or nuclei, ultimately leading to explosive ejections. However, most comets have highly elliptical orbits, meaning they spend most of their orbits in the outer Solar System before moving into the inner Solar System every few decades or centuries. This makes it difficult to determine which comets are cryovolcanic.
Cryovolcanic comets explode when they absorb too much solar radiation. This infrared image shows the explosion of comet 29P/Schwassmann-Wachmann in 2003. NASA/Spitzer Space Telescope
For example, comet 12P/Pons-Brooks, also known as the “Devil Comet,” made its closest approach to the Sun in 71 years, passing our star in April 2024. Since June 2023, when the comet began its rapid plunge into the inner Solar System, its outbursts have been observed repeatedly. But in the previous 69 years, astronomers had never seen one explode.
As a result, astronomers speculate that there are many more cryovolcanic comets lurking in the Oort Cloud, out in the open, and that we will only be able to detect them when they eventually pass closer to the Sun.
Besides the suspected rogue planets, the Sun’s gravitational pull is also capable of attracting other free-floating objects from interstellar space. However, unlike the suspected captured worlds, most of these objects likely pass through our cosmic environment and never return.
Astronomers have already discovered two confirmed interstellar objects: ‘Oumuamua, an elongated object that made headlines in 2017 after some researchers mistakenly suggested it might be an alien probe; and comet 2I/Borisov, discovered in 2019 as it moved through the solar system. Other researchers suspect that a tiny meteor that exploded over Earth in 2014 was also an interstellar alien.
The elongated object ‘Oumuamua was the first interstellar object ever discovered in the Solar System. M. Kornmesser/ESO
Given the pitifully small number of confirmed observations, one might think that interstellar objects are rare. However, some researchers estimate that there are between 1,000 and 10,000 such objects in the Solar System at any given time.
Some researchers have proposed creating dedicated “interstellar interceptor”-type spacecraft that could be launched into orbit around Earth so that scientists could quickly track and study new objects as soon as they are discovered.
The inner solar system is full of potentially hazardous asteroids, which orbit the Sun close enough to Earth to be considered a threat to our planet (though most will never come close). These dangerous space rocks can range in size from “city killers” capable of destroying large population centers to “planet killers” like the one that wiped out the dinosaurs.
Similar massive rocks are found in the Kuiper Belt and beyond. However, unlike comets, asteroids don’t typically migrate in and out of the inner solar system, meaning these rocks pose little threat to us. But that doesn’t mean it’s impossible. If a massive asteroid were to approach Earth, it could also be obscured by the bright sun, depending on its position, giving us very little time for it to approach us undetected.
Asteroids capable of destroying planets could cause catastrophic damage if they ever collide with Earth. NASA Goddard
Scientists have calculated that potentially hazardous asteroids pose no threat to Earth for at least 1,000 years. However, this calculation is based solely on known space rocks.
How the Webb telescope is rewriting our understanding of objects in our solar system—from space rocks in the asteroid belt to the icy and volcanic moons of Jupiter and Saturn.
NASA’s James Webb Space Telescope allows us to peer into the depths of space… and into the past… further than ever before, as it is the largest and most powerful telescope ever sent beyond our planet. It helps us answer important questions about black holes, galaxies, and even the birth of our universe. It took scientists decades to design, build, and launch the telescope. This doesn’t happen often. Every launch of NASA’s new flagship telescope is a huge event for astronomers.
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Some scientists are pointing the Webb telescope in a different direction, a little closer to us, toward objects within our solar system.
All the bright spots on Io are heat emanating from individual volcanoes on the moon; it’s possible to observe how much heat is emitted by each volcano and how it changes over time, and also track eruptions.
For much of astrophysics, the James Webb Space Telescope’s advantage is that it can observe truly, really, really faint objects. The Webb telescope can see beyond visible light, into the infrared spectrum. This allows it to detect dimmer, more distant objects than most telescopes.
One of the main advantages of observing bright objects in the Solar System with the James Webb Space Telescope is that it allows us to observe them without interference from Earth’s atmosphere. Observing through Earth’s atmosphere makes it difficult for ground-based telescopes to see all the details. It’s simply impossible to see all the details without going into space. For example, when searching for signs of water on asteroids and moons.
This particular region of the spectrum is, as you might expect, blocked by water in the Earth’s atmosphere, as well as some carbon dioxide, but thanks to the James Webb Space Telescope, this obstruction is removed, and so it is possible to access information that was previously unseen.
Objects close to the observer, such as planets, appear to move much faster relative to the Webb telescope’s position in space than distant galaxies. To properly view all the passing objects, the Webb telescope must significantly increase its tracking speed. And that’s not the only problem. Some nearby objects are too bright for the Webb telescope to observe. In some modes, the telescope’s detector is completely blinded by the light.
James Webb has access to certain wavelengths that spacecraft instruments have never covered. Specifically, in the case of Io and the Jupiter system, this short-wavelength mid-infrared range has not been covered by any of the missions that have flown past or passed through the Jupiter system. Thus, a small missing piece of Io’s surface spectrum was obtained and large absorption lines from the sulfur dioxide frost covering Io’s surface were detected. Scientists knew sulfur dioxide was present, but hadn’t seen these specific large lines before. They potentially provide information about the texture of the surface frost and may even reveal whether there is a thin layer of frost over a lava flow, for example, versus a thick layer of frost extending several meters.
Asteroids are remnants of the planet-forming period. In many ways, James Webb answers questions about the time of formation, about the very early universe, and about the early stages of solar system formation around other stars. It can also tell us about the early stages of our solar system’s development, even though it happened four and a half billion years ago, because we can study the remnants of that period. These remnants are found throughout the solar system. The icy objects of the outer solar system are called Kuiper belt objects, while the rocky inner ones are called asteroids, and most asteroids are found in the main asteroid belt, which lies between Mars and Jupiter. This is a collection of rocky objects that are essentially material that condensed from the disk from which the planets formed and that has survived relatively intact or completely intact, because most of them are actually fragments, but they did not evolve to form atmospheres, oceans, and so on.
The objects in the Solar System formed at a certain distance from the Sun, in a certain location, or on a certain orbit, and then the Solar System went through a crazy dynamic period where the planets moved from their initial orbits to the orbits they have today. And during this process, all the little objects that condensed from our protoplanetary disk, the planetesimals, were scattered everywhere. And now many of them, from the icy outer regions of the Solar System, have been ejected inward, for example, and are now found in the asteroid belt and elsewhere. And they can tell us about the chemical processes that occurred during planetary formation. They can tell us about the building blocks of Earth and the other planets. And they can also tell us about the process by which the planets move and scatter all these little objects.
In the mid-infrared, researchers are gaining information about the minerals that make up asteroid surfaces, information they haven’t had at this level of detail before. For example, most of these asteroids are actually composed of minerals generally called silicates. This material is similar to lava flows or Earth’s mantle. It’s dominated by a mineral called olivine, which is known as peridot as a gemstone and is also a component of Earth’s mantle. So, this is essentially the dominant mineral we see, but it exists in all these different forms, and the James Webb telescope allows us to determine exactly which form we’re seeing, which can reveal how close to the Sun the mineral originated.
James Webb also studies protoplanetary disks. They also study the heat emanating from these disks, just like that emanating from asteroids. Thus, there are disks that are essentially composed of the same material as asteroids, only four billion years ago.
In addition to Jupiter’s moons, James Webb has made some fascinating observations of Saturn’s moons, particularly Enceladus and Titan. One of Enceladus’s truly fascinating features is the jets of water and other substances erupting from its south pole. These jets were discovered by the Cassini spacecraft, and the James Webb Space Telescope has been studying Enceladus and its plumes. These images measure the amount of water vapor in the plumes, and now we can see that the water vapor extends from Enceladus over a distance many times greater than its size.
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One area where the Webb telescope excels in studying the solar system is mapping the locations of water and carbon dioxide. These so-called volatile compounds are known to be essential for life and planetary evolution. These volatile compounds are not visible from Earth because the Earth’s atmosphere contains water and carbon dioxide, which absorb light at the same wavelengths as other planets. Therefore, one of the Webb telescope’s key discoveries was the distribution of water and carbon dioxide throughout the solar system. It discovered a carbon dioxide atmosphere around Ganymede and was able to map the carbon dioxide atmosphere around Callisto, which was known from spacecraft data but had not previously been mapped. This allows us to see how these atmospheres are distributed across the moons.
A simple guide to planetary sizes based on each planet’s equatorial diameter (width). Each planet’s width is compared to Earth’s equatorial diameter, which is approximately 12,756 kilometers (7,926 miles). The list shows the planets’ order from the Sun outward.
1. Jupiter
Jupiter is the largest planet in the solar system. It is approximately 11 times wider than Earth, and its equatorial diameter is about 142,984 kilometers (88,846 miles). Jupiter is the fifth planet from the Sun, orbiting at an average distance of 778 million kilometers (483.7 million miles). It is approximately five times farther from the Sun than Earth.
On February 12, 2019, NASA’s Juno spacecraft captured three images of the red planet Jupiter, which were used to create this color-enhanced image. At the time of the image, the spacecraft was at altitudes between 26,900 and 95,400 kilometers above Jupiter’s cloud tops. Enhanced image by Kevin M. Gill (CC-BY) based on images courtesy of NASA/JPL-Caltech/SwRI/MSSS.
2. Saturn
Saturn, known for its impressive icy rings, is the second-largest planet in our solar system. It is approximately nine times wider than Earth, with an equatorial diameter of about 120,536 kilometers (74,898 miles). Saturn is the sixth planet from the Sun, orbiting at an average distance of 1.4 billion kilometers (889.8 million miles). It is approximately 9.5 times farther from the Sun than Earth.
NASA’s Cassini spacecraft captured one of its final images of Saturn and its major rings from afar. The images used to create this image were taken on October 28, 2016. The spacecraft arrived at Saturn in 2004, and its mission concluded on September 15, 2017.
3. Uranus
Uranus is the third-largest planet in the Solar System. It is approximately four times wider than Earth and has an equatorial diameter of about 51,118 kilometers (31,763 miles). Uranus is the seventh planet from the Sun, orbiting at an average distance of 2.9 billion kilometers (1.8 billion miles). It is approximately 19 times farther from the Sun than Earth.
A picture of the planet Uranus taken by the Voyager 2 spacecraft in 1986. NASA/JPL-Caltech
4. Neptune
Neptune is the fourth-largest planet. It is approximately four times wider than Earth, and its equatorial diameter is about 49,528 kilometers (30,775 miles). Neptune is the eighth and farthest planet from the Sun, orbiting at an average distance of 4.5 billion kilometers (2.8 billion miles) from the Sun. Neptune is approximately 30 times farther from the Sun than Earth.
This photograph of Neptune was compiled from images taken by NASA’s Voyager 2 spacecraft in the summer of 1989, when it became the first spacecraft to fly by the planet. NASA/JPL-Caltech
5.
Earth Earth is the fifth-largest planet in the Solar System. Its equatorial diameter is approximately 12,756 kilometers (7,926 miles). Earth is the third planet from the Sun, orbiting it at an average distance of 149.7 million kilometers (93 million miles).
This classic photograph of Earth was taken on December 7, 1972, by the crew of the final Apollo mission, Apollo 17, during their flight to the Moon. NASA
6. Venus
Venus is the sixth-largest planet in the Solar System. Its width is approximately equal to that of Earth, and its equatorial diameter is about 12,104 kilometers (7,521 miles). For this reason, Venus is sometimes called Earth’s twin. Venus is the second planet from the Sun, orbiting it at an average distance of 108 million kilometers (67.2 million miles). Venus is approximately 42 million kilometers (26 million miles) closer to the Sun than Earth.
In February 1974, as NASA’s Mariner 10 spacecraft was moving away from Venus, it captured this seemingly peaceful view of Venus. But despite its serene appearance, Venus is a world of intense heat, crushing atmospheric pressure, and clouds of corrosive acid. NASA/JPL-Caltech
7. Mars
Mars, the Red Planet, is the seventh-largest planet in our solar system. Mars is about half the width of Earth and has an equatorial diameter of about 6,792 kilometers (4,221 miles). Mars is the fourth planet from the Sun, orbiting at an average distance of 227.9 million kilometers (141.6 million miles). Mars is approximately 79 million kilometers (49 million miles) farther from the Sun than Earth.
A global mosaic of Mars was created based on images taken by the Viking 1 orbiter in February 1980. The mosaic depicts the entire Valles Marineris canyon system, which runs through the center of Mars. It is more than 3,000 kilometers long, 600 kilometers wide, and 8 kilometers deep. NASA
8. Mercury
Mercury is the smallest planet in our solar system. Its width is just over a third that of Earth, and its equatorial diameter is about 4,880 kilometers. Mercury is the closest planet to the Sun, orbiting it at an average distance of 58 million kilometers. Mercury is 57 million miles closer to the Sun than Earth.
Mercury’s Caloris Basin is clearly visible in this image from NASA’s Messenger spacecraft. Mozart Basin lies south of Caloris. To the center of the globe, Tolstoy Basin is visible. Beethoven Basin is visible along the eastern edge of the globe. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Sizes of dwarf planets
1. Pluto
Pluto is the largest dwarf planet in our solar system, only slightly larger than Eris, the second-largest. Pluto’s equatorial diameter is approximately 2,377 kilometers (1,477 miles). Pluto’s width is approximately 1/5 that of Earth. Pluto orbits the Sun at a distance of approximately 5.9 billion kilometers (3.67 billion miles), which is approximately 39 times farther than the distance from the Sun to Earth.
In this image taken by NASA’s New Horizons spacecraft on July 13, 2015, Pluto nearly fills the frame. It is the final and most detailed image sent back to Earth before the spacecraft’s closest approach to Pluto on July 14, 2015. NASA/JHUAPL/SwRI
2. Eris
Eris is the second-largest dwarf planet, with an equatorial diameter of approximately 2,326 kilometers (1,445 miles). Eris is approximately 1/5 the width of Earth. It orbits the Sun at an average distance of 10 billion kilometers (6.3 billion miles). Eris is approximately 68 times farther from the Sun than Earth.
An artist’s impression of the dwarf planet Eris and its moon Dysnomia. The Sun is a small star in the distance. NASA/JPL-Caltech
3. Haumea
Haumea is the third-largest dwarf planet, with an equatorial diameter of approximately 1,740 kilometers (1,080 miles). Haumea is approximately 1/7 the width of Earth. It orbits the Sun at an average distance of 6.5 billion kilometers (4 billion miles) and is approximately 43 times
This Hubble Space Telescope image shows the dwarf planet Haumea and its two moons, Namaka and Hi’iak, at center. The image was processed using ultraviolet-visible data acquired by Hubble’s Wide Field Camera 3 on June 30, 2015. NASA, ESA, and D. Ragozzine (Brigham Young University); Image processing: Gladys Kober (NASA/The Catholic University of America)
4. Makemake
Makemake, the fourth-largest dwarf planet in the Solar System, has an equatorial diameter of approximately 1,434 kilometers (891 miles). Makemake is one-ninth the width of Earth. Makemake orbits the Sun at an average distance of 6.9 billion kilometers (4.3 billion miles) and is approximately 46 times farther from the Sun than Earth.
This artist’s illustration shows the dwarf planet Makemake and its moon, dubbed MK 2. NASA
5.
Ceres is the smallest dwarf planet, with an equatorial diameter of approximately 964 kilometers (599 miles). Ceres’ diameter is about 1/13 the width of Earth. Ceres is the closest dwarf planet to the Sun and the only dwarf planet in the inner solar system. It orbits the Sun at an average distance of 413 million kilometers (257 million miles). Ceres is approximately 2.8 times farther from the Sun than Earth.
This image of Ceres is part of a sequence of images taken by NASA’s Dawn spacecraft on May 5 and 6, 2015, from a distance of 8,400 miles (13,600 kilometers). NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
List of planets, order and distance from the Sun
Mercury: 36 million miles (58 million kilometers)
Venus: 67.2 million miles (108 million kilometers)
Earth: 93 million miles (149.7 million kilometers)
Mars: 141.6 million miles (227.9 million kilometers)
Dwarf Planet Ceres: 257 million miles (413 million kilometers)
Jupiter: 483.7 million miles (778 million kilometers)
Saturn: 889.8 million miles (1.4 billion kilometers)
Uranus: 1.8 billion miles (2.9 billion kilometers)
Neptune: 2.8 billion miles (4.5 billion kilometers)
Dwarf Planet Pluto: 3.67 billion miles (5.9 billion kilometers)
Dwarf Planet Haumea: 4 billion miles (6.5 billion kilometers)
Dwarf Planet Makemake: 4.3 billion miles (6.9 billion kilometers)
Dwarf Planet Eris: 6.3 billion miles (10 billion kilometers)
A stylized image of our solar system. NASA/JPL
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