what is jupiter's composition of the atmosphere

Jupiter is the fifth planet from our Sun and is, by far, the largest planet in the solar system – more than twice as massive as all the other planets combined. Jupiter's stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.

Jupiter is surrounded by dozens of moons. Jupiter also has several rings, but unlike the famous rings of Saturn, Jupiter’s rings are very faint and made of dust, not ice.

Jupiter, being the biggest planet, gets its name from the king of the ancient Roman gods.

Potential for Life

Jupiter’s environment is probably not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.

While planet Jupiter is an unlikely place for living things to take hold, the same is not true of some of its many moons. Europa is one of the likeliest places to find life elsewhere in our solar system. There is evidence of a vast ocean just beneath its icy crust, where life could possibly be supported.

Size and Distance

With a radius of 43,440.7 miles (69,911 kilometers), Jupiter is 11 times wider than Earth. If Earth were the size of a nickel, Jupiter would be about as big as a basketball.

From an average distance of 484 million miles (778 million kilometers), Jupiter is 5.2 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes Sunlight 43 minutes to travel from the Sun to Jupiter.

Orbit and Rotation

Jupiter has the shortest day in the solar system. One day on Jupiter takes only about 10 hours (the time it takes for Jupiter to rotate or spin around once), and Jupiter makes a complete orbit around the Sun (a year in Jovian time) in about 12 Earth years (4,333 Earth days).

Its equator is tilted with respect to its orbital path around the Sun by just 3 degrees. This means Jupiter spins nearly upright and does not have seasons as extreme as other planets do.

With four large moons and many smaller moons, Jupiter forms a kind of miniature solar system. Jupiter has 80 moons. Fifty-seven moons have been given official names by the International Astronomical Union (IAU). Another 23 moons are awaiting names.

Jupiter's four largest moons – Io, Europa, Ganymede, and Callisto – were first observed by the astronomer Galileo Galilei in 1610 using an early version of the telescope. These four moons are known today as the Galilean satellites, and they're some of the most fascinating destinations in our solar system. Io is the most volcanically active body in the solar system. Ganymede is the largest moon in the solar system (even bigger than the planet Mercury). Callisto’s very few small craters indicate a small degree of current surface activity. A liquid-water ocean with the ingredients for life may lie beneath the frozen crust of Europa, making it a tempting place to explore.

› More on Jupiter's Moons

Discovered in 1979 by NASA's Voyager 1 spacecraft, Jupiter's rings were a surprise, as they are composed of small, dark particles and are difficult to see except when backlit by the Sun. Data from the Galileo spacecraft indicate that Jupiter's ring system may be formed by dust kicked up as interplanetary meteoroids smash into the giant planet's small innermost moons.

Jupiter took shape when the rest of the solar system formed about 4.5 billion years ago when gravity pulled swirling gas and dust in to become this gas giant. Jupiter took most of the mass left over after the formation of the Sun, ending up with more than twice the combined material of the other bodies in the solar system. In fact, Jupiter has the same ingredients as a star, but it did not grow massive enough to ignite.

About 4 billion years ago, Jupiter settled into its current position in the outer solar system, where it is the fifth planet from the Sun.

The composition of Jupiter is similar to that of the Sun – mostly hydrogen and helium. Deep in the atmosphere, pressure and temperature increase, compressing the hydrogen gas into a liquid. This gives Jupiter the largest ocean in the solar system – an ocean made of hydrogen instead of water. Scientists think that, at depths perhaps halfway to the planet's center, the pressure becomes so great that electrons are squeezed off the hydrogen atoms, making the liquid electrically conducting like metal. Jupiter's fast rotation is thought to drive electrical currents in this region, generating the planet's powerful magnetic field. It is still unclear if deeper down, Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. It could be up to 90,032 degrees Fahrenheit (50,000 degrees Celsius) down there, made mostly of iron and silicate minerals (similar to quartz).

As a gas giant, Jupiter doesn’t have a true surface. The planet is mostly swirling gases and liquids. While a spacecraft would have nowhere to land on Jupiter, it wouldn’t be able to fly through unscathed either. The extreme pressures and temperatures deep inside the planet crush, melt, and vaporize spacecraft trying to fly into the planet.

Jupiter's appearance is a tapestry of colorful cloud bands and spots. The gas planet likely has three distinct cloud layers in its "skies" that, taken together, span about 44 miles (71 kilometers). The top cloud is probably made of ammonia ice, while the middle layer is likely made of ammonium hydrosulfide crystals. The innermost layer may be made of water ice and vapor.

The vivid colors you see in thick bands across Jupiter may be plumes of sulfur and phosphorus-containing gases rising from the planet's warmer interior. Jupiter's fast rotation – spinning once every 10 hours – creates strong jet streams, separating its clouds into dark belts and bright zones across long stretches.

With no solid surface to slow them down, Jupiter's spots can persist for many years. Stormy Jupiter is swept by over a dozen prevailing winds, some reaching up to 335 miles per hour (539 kilometers per hour) at the equator. The Great Red Spot, a swirling oval of clouds twice as wide as Earth, has been observed on the giant planet for more than 300 years. More recently, three smaller ovals merged to form the Little Red Spot, about half the size of its larger cousin.

Findings from NASA’s Juno probe released in October 2021 provide a fuller picture of what’s going on below those clouds. Data from Juno shows that Jupiter’s cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.

The findings also indicate these storms are far taller than expected, with some extending 60 miles (100 kilometers) below the cloud tops and others, including the Great Red Spot, extending over 200 miles (350 kilometers). This surprising discovery demonstrates that the vortices cover regions beyond those where water condenses and clouds form, below the depth where sunlight warms the atmosphere.

The height and size of the Great Red Spot mean the concentration of atmospheric mass within the storm potentially could be detectable by instruments studying Jupiter’s gravity field. Two close Juno flybys over Jupiter’s most famous spot provided the opportunity to search for the storm’s gravity signature and complement the other results on its depth.

With their gravity data, the Juno team was able to constrain the extent of the Great Red Spot to a depth of about 300 miles (500 kilometers) below the cloud tops.

Belts and Zones In addition to cyclones and anticyclones, Jupiter is known for its distinctive belts and zones – white and reddish bands of clouds that wrap around the planet. Strong east-west winds moving in opposite directions separate the bands. Juno previously discovered that these winds, or jet streams, reach depths of about 2,000 miles (roughly 3,200 kilometers). Researchers are still trying to solve the mystery of how the jet streams form. Data collected by Juno during multiple passes reveal one possible clue: that the atmosphere’s ammonia gas travels up and down in remarkable alignment with the observed jet streams.

Juno’s data also shows that the belts and zones undergo a transition around 40 miles (65 kilometers) beneath Jupiter’s water clouds. At shallow depths, Jupiter’s belts are brighter in microwave light than the neighboring zones. But at deeper levels, below the water clouds, the opposite is true – which reveals a similarity to our oceans.

Polar Cyclones Juno previously discovered polygonal arrangements of giant cyclonic storms at both of Jupiter’s poles – eight arranged in an octagonal pattern in the north and five arranged in a pentagonal pattern in the south. Over time, mission scientists determined these atmospheric phenomena are extremely resilient, remaining in the same location.

Juno data also indicates that, like hurricanes on Earth, these cyclones want to move poleward, but cyclones located at the center of each pole push them back. This balance explains where the cyclones reside and the different numbers at each pole.

Magnetosphere

The Jovian magnetosphere is the region of space influenced by Jupiter's powerful magnetic field. It balloons 600,000 to 2 million miles (1 to 3 million kilometers) toward the Sun (seven to 21 times the diameter of Jupiter itself) and tapers into a tadpole-shaped tail extending more than 600 million miles (1 billion kilometers) behind Jupiter, as far as Saturn's orbit. Jupiter's enormous magnetic field is 16 to 54 times as powerful as that of the Earth. It rotates with the planet and sweeps up particles that have an electric charge. Near the planet, the magnetic field traps swarms of charged particles and accelerates them to very high energies, creating intense radiation that bombards the innermost moons and can damage spacecraft.

Jupiter's magnetic field also causes some of the solar system's most spectacular aurorae at the planet's poles.

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11.1: Jupiter's Atmosphere

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Jupiter is known for its multi-colored bands. The atmosphere of Jupiter has bright zones and dark belts . The zones are cooler and are higher than belts. A stable flow of gases underlies the zones and bands, called zonal flow . Cooler gases sink in the atmosphere, creating the dark belts while warmer gases rise, creating the lighter zones. Different compounds in atmosphere produce clouds of different colors. For example, ammonium sulfide clouds (NH 4 SH) reflect red/brown while ammonia in the highest, coldest layer, reflects white. Because Jupiter does not have a solid surface, when modeling its atmosphere, astronomers take the top of the troposphere as the 0 km mark and then map all positives based on how far above or below that mark they are.

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The composition of Jupiter’s atmosphere is as follows:

• 89.8% Hydrogen (H 2 )
• 10.2% Helium
• ~0.3% Methane
• ~0.026% Ammonia
• ~0.003% Hydrogen deuteride (HD)
• 0.0006% Ethane
• 0.0004% water
• Ices on Jupiter include ammonia, water, ammonium, hydrosulfide(NH 4 SH)

In December of 1995, the Galileo probe entered Jupiter’s atmosphere and collected data for 57 minutes. The data from the probe revealed Jupiter's atmosphere had roughly the same percentage of hydrogen and helium as the Sun. The Galileo probe also found that Jupiter appears to have more carbon, nitrogen, sulfur, and other heavy elements, than the Sun. It is likely that these elements may come from interplanetary bodies like comets and asteroids that strike Jupiter. The Galileo probe found few organic molecules.

Hydrogen compounds in Jupiter form clouds. Different cloud layers correspond to freezing points of different hydrogen compounds. These cloud layers include, in descending order, ammonia (40-50 km below the top of the troposphere), ammonium hydrosulfide (60-70 km below the top of the troposphere), and water (~100 km below the top of the troposphere). Jupiter’s lowest cloud layer cannot be seen by optical telescopes. Measurements taken by Galileo probe show high wind speeds even at great depth. These are likely due to heating from the interior of the planet instead of from the Sun.

Jupiter’s most striking feature is the Great Red Spot. This storm system is twice as wide as Earth. It is at least three centuries old as astronomers first noted its existence three hundred years ago and it is still there. Unlike on Earth, where hurricanes lose energy as they pass over colder water or make landfall, Jupiter’s lake of a solid surface produces instabilities that can last for centuries.

https:/www.flickr.com/photos/kevinmgill/49856445171; 

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All About Jupiter

Jupiter is a stormy planet that is probably best known for its Great Red Spot. The spot is actually a giant, wild storm that has been raging for more than 300 years. Credit: NASA/JPL-Caltech

Jupiter is the biggest planet in our solar system. It's similar to a star, but it never got massive enough to start burning. It is covered in swirling cloud stripes. It has big storms like the Great Red Spot, which has been going for hundreds of years. Jupiter is a gas giant and doesn't have a solid surface. It is still unclear if deeper down, Jupiter has a central core of solid material or if it may be a thick, super-hot and dense soup. Jupiter also has rings, but they're too faint to see very well.

Explore Jupiter! Click and drag to rotate the planet. Scroll or pinch to zoom in and out. Credit: NASA Visualization Technology Applications and Development (VTAD)

Credit: NASA/JPL-Caltech

Structure and Surface

• Jupiter is the biggest planet in our solar system. It is actually more than twice as massive than the other planets of our solar system combined.
• Jupiter is a gas giant. It is made mostly of hydrogen and helium.
• Jupiter has a very thick atmosphere.
• Jupiter has rings, but they’re very hard to see.
• The giant planet's Great Red Spot is a centuries-old storm bigger than Earth.

Time on Jupiter

• One day on Jupiter goes by in just 10 hours.
• One year on Jupiter is the same as 11.8 Earth years.

Jupiter's Neighbors

• Jupiter has 95 officially recognized moons.
• Jupiter is the fifth planet from the Sun. That means Mars and Saturn are Jupiter’s neighboring planets.

Quick History

• Jupiter has been known since ancient times because it can easily be seen with just our eyes. No special equipment is needed.
• Jupiter has been visited or passed by several spacecraft , orbiters and probes, such as Pioneer 10 and 11, Voyager 1 and 2, Cassini, New Horizons, and Juno.
• Jupiter has auroras , just like Earth! Not only are the auroras huge in size, they are also hundreds of times more energetic than auroras on Earth. And, unlike those on Earth, they never cease.

What does Jupiter look like?

This striking view of Jupiter's Great Red Spot and turbulent southern hemisphere was captured by NASA's Juno spacecraft as it performed a close pass of the gas giant planet. Credit: Enhanced image by Kevin M. Gill (CC-BY) based on images provided courtesy of NASA/JPL-Caltech/SwRI/MSSS

Astronomers are using NASA's Hubble Space Telescope to study auroras — stunning light shows in a planet's atmosphere — on the poles of the largest planet in the solar system, Jupiter. Credits: NASA, ESA, and J. Nichols (University of Leicester)

This new Hubble Space Telescope view of Jupiter, taken on June 27, 2019, reveals the giant planet's trademark Great Red Spot, and a more intense color palette in the clouds swirling in Jupiter's turbulent atmosphere than seen in previous years. The colors, and their changes, provide important clues to ongoing processes in Jupiter's atmosphere. Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

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What is Jupiter made of?

Composed predominantly of hydrogen and helium, the massive Jupiter is much like a tiny star. But despite the fact that it is the largest planet in the solar system, the gas giant just doesn't have the mass needed to push it into stellar status.

The surface of Jupiter

When scientists call Jupiter a gas giant, they aren't exaggerating. If you parachuted into Jupiter in hopes of hitting the ground, you would never find firm landing. The atmosphere of Jupiter is 90 percent hydrogen. The remaining 10 percent is almost completely made up of helium, though there are small traces of other gases inside.

These gases pile on top of one another, forming layers that extend downward. Because there is no solid ground, the surface of Jupiter is defined as the point where the atmospheric pressure is equal to that of Earth. At this point, the pull of gravity is almost two and a half times stronger than it is on our planet.

Trying to stand on that surface would be impossible, since it is simply another layer of gases. Spacecraft and astronauts would only sink into the mire. A probe or spacecraft traveling farther toward the center of the planet would continue to find only thick clouds until it reached the core.

Jupiter's core

Details about Jupiter's core remain a challenge to find. Scientists think that the dense central core may be surrounded by a layer of metallic hydrogen, with another layer of molecular hydrogen on top.

Scientists aren't certain of just how solid Jupiter's core might be. While some theorize that the core is a hot molten ball of liquid, other research indicates that it could be a solid rock 14 to 18 times the mass of the Earth. The temperature at the core is estimated to be about 35,000 degrees Celsius (63,000 degrees Fahrenheit).

Discussions about Jupiter's core didn't even begin until the late 1990s, when gravitational measurements revealed that the center of the gas giant was anywhere from 12 to 45 times the mass of Earth. And just because it had a core in the past doesn't mean that it still will today – new evidence suggests that the gas giant's core may be melting.

Not quite a star

Like the sun, Jupiter is composed predominantly of hydrogen and helium. But unlike the sun, it lacks the necessary amount to begin fusion , the process that fuels a star. Jupiter would need to be 75 to 80 times more massive than it is at present to be considered a star. If all of the planets in the solar system had formed as part of the gas giant, it still would not have sufficient mass. Still, by itself, Jupiter is two and a half times larger than all of the other planets in the solar system combined.

— Nola Taylor Redd, SPACE.com Contributor

• How Far Away is Jupiter?
• Jupiter's Atmosphere: Composition & the Great Red Spot
• How Was Jupiter Formed?
• What is the Temperature of Jupiter?
• How Big is Jupiter?

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Nola Taylor Tillman is a contributing writer for Space.com. She loves all things space and astronomy-related, and enjoys the opportunity to learn more. She has a Bachelor’s degree in English and Astrophysics from Agnes Scott college and served as an intern at Sky & Telescope magazine. In her free time, she homeschools her four children. Follow her on Twitter at @NolaTRedd

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Gravity assist: it’s raining diamonds on these planets.

Uranus and Neptune are two of the many exciting and mysterious objects in our universe that the James Webb Space Telescope will soon begin to explore. Learn more about these planets and the Webb telescope’s upcoming observations from astrophysicist Naomi Rowe-Gurney, our guest on this week’s Gravity Assist.

Listen to the Podcast

Uranus and Neptune are two of the many exciting and mysterious objects in our universe that the James Webb Space Telescope will soon begin to explore. Temperature and pressure conditions are so extreme on these planets that carbon atoms could be crushed into diamonds in their atmospheres. And did you know that Uranus orbits on its side? Learn more about these planets and the Webb telescope’s upcoming observations from astrophysicist Naomi Rowe-Gurney, our guest on this week’s Gravity Assist.

Jim Green: We have two ice giant planets in our solar system, Uranus and Neptune. What will we find out about them when the James Webb Space Telescope takes a look?

Naomi Rowe Gurney: That will give us a massive insight into these other solar systems that we’re seeing.

Naomi Rowe Gurney: I had so many teachers and tutors, and just people in my life that said:

Naomi Rowe Gurney: Maybe science is a little bit hard. Like, try doing something else. And I’m really glad that I didn’t listen to them and I let my heart decide.

Jim Green: Hi, I’m Jim Green, and this Gravity Assist, NASA’s interplanetary talk show. We’re going to explore the inside workings of NASA and meet fascinating people who make space missions happen.

Jim Green: I’m here with Naomi Rowe-Gurney. And she is a postdoctoral research associate at NASA’s Goddard Space Flight Center, through the Howard University in Washington, DC. Now, she specializes in the study of two of my favorite planets, Uranus, and Neptune. And she’ll be using the Webb Telescope to find out more about these fabulous ice giants of our solar system. So welcome, Naomi, to Gravity Assist.

Naomi Rowe-Gurney: Thank you so much for having me. I’m really excited to be here.

Jim Green: Well, I’ve got to tell you, you know, we just haven’t been back to the ice giants in so long after Voyager 2 flew by both of them [in the 1980s]. Not Voyager 1, Voyager 1 went on its way. But only Voyager 2 has observed, you know, those two beautiful ice giants. And you’ve been studying those for a long time. What is your favorite aspects of these ice giants? And why do we call them that? Why aren’t they just gas giants?

Naomi Rowe-Gurney: Yeah, so I love the ice giants. I think I love them mostly because they haven’t been looked at very much. I initially wanted to do my PhD on these two planets because there were so many unanswered questions. And we just really don’t know even like the fundamentals of where they came from, and why they are the way they are, and why they’re called ice giants. I mean, people are still kind of debating that name and whether it’s appropriate and whether they should really be called rock giants, because who knows what’s inside?

Naomi Rowe-Gurney: It really takes a mission, a proper mission with like an orbiter to look at the gravity of a planet to be able to figure out what’s happening on the inside.

Jim Green: Now the composition of the atmosphere has kind of given us that clue that they’re different than Jupiter and Saturn. And that’s because it’s got a variety of ices.

Naomi Rowe-Gurney: Mhm.

Jim Green: And you’ve been working on the thermal structure and composition, what is the most exciting things that you’ve been finding out?

Naomi Rowe-Gurney: Yeah, so that’s the reason why they’re blue, because they have high levels of methane in their atmosphere. I study the middle atmosphere, which is like the stratosphere and the upper troposphere. And that’s kind of down to around one bar, which is around the same pressure that we have here on Earth, on air. So that’s kind of the level that I look at.

Naomi Rowe-Gurney: And what we see there is that the Sun interacts with the methane in the atmosphere, and it breaks down the methane into lots of different hydrocarbons. So lots of these chains of different things with hydrogen and carbon in [them], with lots of fancy names like diacetylene and acetylene and methylacetylene, all of these. And we still don’t really know everything, like the composition of everything that’s in there, and we’re still finding new things all the time. And that’s why the JWST is so exciting, because we are going to be able to see a lot more of what’s going on, and a lot more of these like complex hydrocarbons and things.

Jim Green: A couple of news releases that I’ve seen have concepts where carbon gets hardened, almost to the point, or maybe to the point of being diamonds. Do we see those kinds of things and Uranus and Neptune’s atmospheres?

Naomi Rowe-Gurney: So I mentioned methane being the reason why these two planets are blue. Well, methane has carbon in it and that carbon can occur by itself and also be crushed by the immense pressures that happen, like, deep in the atmosphere, so much deeper than the levels that I look at. And inside the planet, when it gets really hot and really dense, these, these diamonds form and accumulate, and then they become even heavier. And that means that they kind of rain down in the atmosphere. But it’s not the rain that we see here because these pressures are extreme, and you’ll never be able to get there as a human. So even if these diamonds do exist, we would never be able to go and grab them. So… unfortunately.

Jim Green: Yeah, unfortunately. Okay. (laughs)

Jim Green: Well, you know, one of the really exciting things about planetary science is that when we go from planet to planet, we look at some things that are similar, in addition to the differences. And one thing we look for is lightning. Now here on Earth, we see our lightning but in the upper atmosphere there’s some really spectacular forms like “sprites,” we call them and “elves” and blue “jets” and all kinds of exotic discharges that happen in our own atmosphere. Do you think we’ll find those at Uranus and Neptune?

Naomi Rowe-Gurney: Yeah, definitely. I think that there’s already been some research done on the kind of traces that we find in, in chemicals that is left behind by lightning and things. That research has already been done using some ground-based telescopes. So that is exciting stuff that’s already happening on Uranus and Neptune that we’re seeing. The lightning on other planets is similar, I think, to the lightning that we have on Earth as well. So all of those, like elves and sprites and things are also things that we’re trying to look for, on, on other planets like Jupiter, Saturn, Uranus, and Neptune.

Jim Green: Well, you know, I think the Voyagers using the plasma wave experiment, did indeed find lightning, at least at Neptune, and at Uranus. That’s really exciting. So, so that changes chemistry, too, in the atmosphere.

Jim Green: One of the one of the really great things that that have happened, is we’ve been monitoring Uranus and Neptune with Hubble, you know. So we have many years of Uranus and Neptune data. Hubble observed some big spots on Neptune recently. What’s that all about?

Naomi Rowe-Gurney: Yeah, so Hubble looks at the near-infrared and the visible wavelengths and in visible we can look at what’s happening in every color that we can see with our eyes. So these spots on Uranus and Neptune appear as like these blue dark spots, just like the “great dark spot” that we saw with Voyager on Neptune. And we are trying to observe as many of these as possible, because we think they’re kind of like the Great Red Spot that’s on Jupiter, like a big storm system that creates lots of changes in the atmosphere, in all levels of the atmosphere. And it’s still unknown as to how a dark spot changes the upper levels and, and changes the chemistry and the circulation going on.

Naomi Rowe-Gurney: So that’s a major thing that the JWST is going to be looking at, because we’re using the mid-infrared in with JWST. And the mid-infrared is really interesting because it senses a little bit higher up than those visible and near-infrared wavelengths in the stratosphere. And that’s where all of that interesting chemistry is going on that I was talking about. And that we think is also being affected by these dark spots that might be these circular storms that are happening.

Naomi Rowe-Gurney: And that’s actually what my PhD was looking at with Spitzer. But the problem with Spitzer is that it’s so small, it’s only like naught-point eight five [0.85] meters in diameter, so less than, less than a meter and…

Jim Green: The telescope mirror itself.

Naomi Rowe-Gurney: Yeah, exactly. And that’s actually the same size as the secondary mirror of the JWST. So the mirror that is used to focus the big 6.5-meter mirror is the same size as the Spitzer’s major mirror. So.

Jim Green: Wow. Yeah, that’s a good metric. (laughs)

Naomi Rowe-Gurney: Yeah, right? That is a massive advantage. Because with Spitzer, we didn’t have any images, because they’re so far away, both Uranus and Neptune are so far. And they’re also quite cold, it means that we only had like a point of light. So we can look at it like we look at a star in the night sky. That’s how far away they are. And all we get is one spectrum. So one piece of light for just the whole planet.

Jim Green: So Hubble has been observing Uranus and Neptune. But there are specific proposals that come in and do that. Have you been involved in any of those?

Naomi Rowe-Gurney: Yes. So just recently, in fact, today, this morning, I found out that one of my proposals that I sent in to observe the ice giants is has been approved on HST 30. So cycle 30, which is really, really exciting, like Hubble Space Telescope is amazing. It was launched in 1990. And actually, that makes it the same age as me, which always makes me feel very, both old and also very young. (laughs)

Jim Green: Yes, indeed!

Naomi Rowe-Gurney: Yeah! So yeah, my project is going to be using Hubble to look at Uranus and Neptune to kind of increase the science that we have for, with the JWST. So it’s going to be looking at them, hopefully as close as possible to the JWST observations. And that will mean that we are getting even more wavelengths in there because JWST is looking at the mid-infrared, and near-infrared, but Hubble has capabilities all the way down to the visible, which is really exciting because using visible and also some of the near-infrared. So we can expand that that window and also the depths that we’re looking at in the atmosphere.

Jim Green: Wow, perfect.

Jim Green: You know, one of the things that really fascinated me about Uranus and Neptune is the heat that they produce. You know, all our planets are hot on the inside, they’re still cooling off from when they were made 4.6 billion years ago. But Neptune, correct me if I’m not right, is producing more heat on the inside than Uranus is. Do we know what’s happening?

Naomi Rowe-Gurney: That’s true. So it’s actually Uranus that’s the weird one. Neptune is, is creating the amount of heat on the inside that we would expect a planet to make.

Jim Green: Ah, thank you for correcting me, yeah.

Naomi Rowe-Gurney: Just like on Earth, we have like things like the mantle happening inside. It’s like the remnant of the, the creation of the planet is still hot on the inside and it’s only very slowly cooling down. And that’s what we expect to see with all of the other planets as well — a hot interior leftover from creation. And that’s not what we see at Uranus. We see a negligible internal heat. So it looks like there’s no internal heat really going on at all inside. And that’s very strange. And one explanation is that Uranus was hit by something really big, and kind of turned inside out. And all of that internal heat got lost.

Naomi Rowe-Gurney: And that would also explain why the planet is on its side, which is also another weird and very unique thing in the solar system. No other planet is just on its side spinning, like, on its axis in the wrong direction.

Jim Green: That’s fantastic. Well, you know, we’ve been looking at planets beyond our own in our own solar system, and Kepler came out with some amazing results. And those results indicated the distribution of planets that we see in other solar systems. And I always thought, “Oh, well, we got to be seeing oh, you know, a bunch of Jupiter’s.” but it turns out Jupiter’s now you know, big Jupiter’s are not one of the common planets. But indeed, more of what we call Super Earths, but also mini-Neptune. And so the ice giants Uranus, and Neptune hold a really special place in terms of how important that might be for other solar systems. What can you tell me about those kinds of capabilities?

Naomi Rowe-Gurney: Yeah, so that’s a major motivation behind looking at our own ice giants and why the entire planetary science community and science community is so interested in both of these planets now, it’s because we found so many of these Neptune-sized or Uranus-sized, just ice giant sized planets in other solar systems. And we can look at our own ice giants and try and understand a little bit more about how they’re formed, and their place in our solar system and how they got there. And that will give us a massive insight into these other solar systems that we’re seeing.

Jim Green: You know, right after Webb’s launch on December 25, man, you must have been busy!

Naomi Rowe-Gurney: Yeah, so straight off the launch, I didn’t have too much to do with launch. That was all the engineers and ESA doing all of that. But then after that first stage, we did deployment. That was like the first phase of commissioning is what we call it. This phase, this six-month phase, getting the telescope ready for science is called commissioning. And so that first stage was deployment, getting the telescope through to the L2 Lagrange point, which is where it all bits, which is 1.5 million kilometers away from here to make sure that the telescope’s nice and cold, so they can see everything that it’s looking at in its infrared images.

Naomi Rowe-Gurney: And then after that, when it reached there and deployed successfully, then after phase two, is the telescope alignment. So where it made all of these 18 separate movable segments into one seamless, like, giant 6.5-meter mirror. And then the third stage is the stage that I’ve been involved in, which is the science instrument commissioning. And I’ve been involved in a team called the Moving Target Vommissioning Team. And that means that we have been looking at asteroids. So asteroids that are in that asteroid belt mostly, and making sure that the telescope is able to track things that are moving, because everything in the solar system compared to distant objects is a moving target. And it means that the telescope actually has to move physically as it is looking at these objects. And that is definitely needed for everything in the solar system. So that’s what we’ve been testing in this last phase, and then that will be over soon. And then those first images come out on the 12th of July, which is very exciting.

Jim Green: So the first light science from JWST is going to be shown July 12. And then from then on, we’re going to see all kinds of fantastic stuff coming out in this regular schedule that it has. So when will Webb start looking at solar system objects?

Naomi Rowe-Gurney: So it won’t be part of those first images that come out on the 12th of July. But we will actually start to look at solar system objects. It’s just those images won’t be released to scientists until after that 12th of July date, and then they won’t be released as, kind of, science or anything until our scientists have done their analysis and calibration and everything. So probably, we’ll see those first things come out at the end of the summer, I would say, is optimistic.

Jim Green: Now, one of your jobs is, you’re a JWST Solar System ambassador.

Naomi Rowe-Gurney: Yes.

Jim Green: So tell me what that’s all about? And what are you doing?

Naomi Rowe-Gurney: So I help everybody who has guaranteed time observations, which means observations in this first year of the James Webb’s lifetime. And so everybody who is using JWST to look at solar system objects, or at planetary systems. So all four giant planets, Mars, also the rings, and all of the moons as well. So those ocean worlds and Titan and icy moons, and smaller moons as well of Saturn we’re going to be looking at. And I am there to kind of assist people in going from data all the way through to getting their science published.

Jim Green: Well, so you’ll be right on top of some of the latest discoveries.

Naomi Rowe-Gurney: Yeah, I hope so.

Jim Green: Wow, that’s fantastic. I know this is going to be such an exciting time for our scientists, and for NASA with a telescope so large, looking at wavelengths that we cannot see from the ground. Well, Naomi, I always like to ask my guests to tell me the person, place or event that propelled them to become the scientists they are today. And I call that event a Gravity Assist. So Naomi, what was your Gravity Assist?

Naomi Rowe-Gurney: My gravity assist was an event-slash-place. It was when I was about five years old, I went to the planetarium in London. And I hadn’t really thought about Earth or space or anything like that before then. And it just completely opened my mind. And I was just obsessed with space ever since then. And I loved cosmology, and astrophysics and planetary science and even Earth science. I was just obsessed with it. And I went through my entire school life, loving science, being terrible at math, but going through it just because I really wanted to do science. And obviously getting to where I am today, because of that first, yeah, gravity assist from the planetarium in London. So, love them.

Jim Green: Wow, that’s, that’s really neat. And I have to comment on your math mention, because there’s so much different types of math. You know, not all math is created equal, so to speak.

Jim Green : I was horrible in geometry. I just did not like it. But I mean, give me a differential equation, and I’ll solve it.

Naomi Rowe-Gurney: I’m the same. I hate numbers. I still count on my fingers because numbers just don’t make sense to me. So I’m great at algebra, though. So yeah…it’s all different types of math, so…

Jim Green : It is, it is. So I always encourage, kids in school to look past that not to be discouraged, because they have trouble in one area of math, because they’ll find out that in the end, the kind of math that they can really get into will help them be the scientists that they are, or the engineer that they are, in their future life.

Naomi Rowe-Gurney: Definitely.

Jim Green : So, so those challenges are important to overcome.

Naomi Rowe-Gurney: Yeah, I would say my advice would be: Don’t listen to people when they say that you can’t do something. I had so many teachers and tutors, and just people in my life that said, “Maybe you should do something a bit easier. Maybe you should, I don’t know, like, pick a different subject. Maybe maths isn’t for you, you know, maybe science is a little bit hard, like try doing something else. And I’m really glad that I didn’t listen to them. And I let my heart decide that even if it was hard, I was going to try. And I thankfully have a very supportive family that were always very supportive of me.

Jim Green: Well, Naomi, thanks so much for telling us about that fantastic science of these gas giants. And the JWST is going to give us so much more information about them.

Naomi Rowe-Gurney: Thank you so much for having me. This has been great.

Jim Green: Well join me next time as we continue our journey to look under the hood at NASA and see how we do what we do. I’m Jim Green, and this is your Gravity Assist.

Lead producer : Elizabeth Landau

Audio engineer : Manny Cooper

Planet Sizes and Locations in Our Solar System

Our solar system has eight planets, and five officially recognized dwarf planets . Which planet is biggest? Which is smallest? What is the order of the planets as we move out from the Sun?

This is a simple guide to the sizes of planets based on the equatorial diameter – or width – at the equator of each planet. Each planet’s width is compared to Earth’s equatorial diameter, which is about 7,926 miles (12,756 kilometers).

At the bottom of the page, there is a handy list of the order of the planets moving away from our Sun.

Sizes of Planets

Jupiter is the largest planet in the solar system. It’s about 11 times wider than Earth with an equatorial diameter of 88,846 miles (about 142,984 kilometers). Jupiter is the fifth planet from the Sun, orbiting at an average distance of 483.7 million miles (778 million kilometers). It’s about five times farther from the Sun than Earth.

Explore Jupiter

Saturn, known for its spectacular icy rings, is the second largest planet in our solar system. It’s about nine times wider than Earth, with an equatorial diameter of about 74,898 miles (about 120,536 kilometers). Saturn is the sixth planet from the Sun, orbiting at an average distance of 889.8 million miles (1.4 billion kilometers). It’s about 9.5 times farther from the Sun than Earth.

Explore Saturn

Uranus is the third largest planet in our solar system. It’s about four times wider than Earth, and has an equatorial diameter of about 31,763 miles (51,118 kilometers). Uranus is the seventh planet from the Sun, orbiting at an average distance of 1.8 billion miles (2.9 billion kilometers). It’s about 19 times farther from the Sun than Earth. 

Explore Uranus

Neptune is the fourth largest planet. It’s about four times wider than Earth with an equatorial diameter of about 30,775 miles (49,528 kilometers). Neptune is the eighth, and the most distant planet from the Sun, orbiting at an average distance of 2.8 billion miles (4.5 billion kilometers). Neptune is about 30 times farther from the Sun than Earth. 

Explore Neptune

Earth is the fifth largest planet in the solar system. It has an equatorial diameter of about 7,926 miles (12,756 kilometers). Earth is the third planet from the Sun, orbiting at an average distance of 93 million miles (149.7 million kilometers).

Explore Earth

Venus is the sixth largest planet in the solar system. Venus is about the same width as Earth, and has an equatorial diameter of about 7,521 miles (12,104 kilometers). For this reason, Venus is sometimes known as Earth’s twin. Venus is the second planet from the Sun, orbiting at an average distance of 67.2 million miles (108 million kilometers). Venus is about 26 million miles (42 million kilometers) closer to the Sun than Earth.  

Explore Venus

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 4,221 miles (6,792 kilometers). Mars is the fourth planet from the Sun, orbiting at an average distance of 141.6 million miles (227.9 million kilometers). Mars is about 49 million miles (79 million kilometers) farther from the Sun than Earth.

Explore Mars

Mercury is the smallest planet in our solar system. Mercury is a little more than one-third the width of Earth, and has an equatorial diameter of about 3,032 miles (4,880 kilometers). Mercury is the closest planet to the Sun, orbiting at an average distance of 36 million miles (58 million kilometers). Mercury is 57 million miles closer to the Sun than Earth.

Explore Mercury

Sizes of Dwarf Planets

Pluto is the largest dwarf planet in our solar system, just slightly larger than Eris, at number two. Pluto has an equatorial diameter of about 1,477 miles (2,377 kilometers). Pluto is about 1/5th the width of Earth. Pluto orbits the Sun at a distance of about 3.67 billion miles (5.9 billion kilometers), or about 39 times farther away than Earth from the Sun.

Explore Pluto

Eris is the second largest dwarf planet with an equatorial diameter of about 1,445 miles (about 2,326 kilometers). Eris is about 1/5th the width of Earth. It orbits the Sun from an average distance of 6.3 billion miles (10 billion kilometers). Eris is about 68 times farther from the Sun than Earth.

Explore Eris

Haumea is the third largest dwarf planet with an equatorial diameter of about 1,080 miles (about 1,740 kilometers). Haumea is about 1/7 the width of Earth. It orbits the Sun from an average distance of 4 billion miles (6.5 billion kilometers), and it’s about 43 times farther from the Sun than Earth.

Explore Haumea

The fourth largest dwarf planet in the solar system, Makemake has an equatorial diameter of about 891 miles (about 1,434 kilometers). Makemake is 1/9 the width of Earth. Makemake orbits the Sun from an average distance of 4.3 billion miles (6.9 billion kilometers), and it’s about 46 times farther from the Sun than is Earth.

Explore Makemake

Ceres is the smallest dwarf planet with an equatorial diameter of about 599 miles (about 964 kilometers). Ceres is about 1/13 the width of Earth. The closest dwarf planet to the Sun, Ceres orbits the Sun from an average distance of 257 million miles (413 million kilometers), and it’s about 2.8 times farther from the Sun than Earth.

Order of Planets and Dwarf Planets - 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)

Explore More

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The rover has arrived at an area that may show evidence liquid water flowed on this part of Mars for much longer than previously thought. NASA’s Curiosity rover has begun exploring a new region of Mars, one that could reveal more about when liquid water disappeared once and for all from the Red Planet’s surface. […]