Astronomy Semester 2 Module 3: Outer Planets: Jupiter and Saturn

How many Earths would fit in Jupiter?

1300; you could fit more than 700 Earths inside Saturn, 63 Earths inside Uranus, 57 Earths inside Neptune, and over 1,300 Earths would fit inside Jupiter!

How large is Jupiter in Diameter?

142,984 kilometers (88,846 miles) in diameter with an enormous magnetic field

How many moons does Jupiter have?

53 confirmed moons (in the lesson) 79 moons (from research)

Saturn's Great White Spot

A white oval close to the equator and observed on Saturn's atmosphere by the Hubble Space Telescope in 1991 was given the nickname "Great White Spot." Not very original, but easy to remember! A similar storm occurs once every year in Saturn but keep in mind that one Saturn year is equivalent to 30 Earth years, so the next storm should occur in the year 2020.

Saturn's Density

Although Saturn is just a bit smaller than Jupiter in diameter, it has much less density and volume than Jupiter. In fact, although it is the second-largest planet, Saturn is the only planet in the solar system with a density that is less than water. This means that if you could find a bathtub or pool big enough to fit Saturn inside it, Saturn would float on top of the water! Saturn's magnetic field is 578 times (36,184 miles) that of Earth's. The planet's mean radius is 58,232 kilometers, and its mass is about 95 times the mass of Earth. In images brought back by the Cassini spacecraft, the northern hemisphere of the planet appears bright blue in color. We can't see this color on Earth because Saturn's rings block it.

Saturn's rings composition

Although Saturn's rings appear to be solid when looking at them from afar, it is believed that the rings are made from pieces of asteroids and comets or perhaps shattered moons that broke up before they reached the planet. The particles that make up the rings vary from very small grains to particles that are as large as mountains.

Jupiter's Moon Europa

Astronomers are now fascinated with Europa because water vapor has been discovered on that moon. Future missions will include specialized equipment such as radar that can cut through the icy frozen crust of Europa and determine what lies beneath. Etymology: Europa was another woman who caught the attention of Zeus/Jupiter. Zeus took the form of a bull, enticed Europa into sitting on his back, and then kidnapped her. Her plight is one of the more popular subjects for various artists across the ages, and you can probably guess which continent was inspired by her name!

What happens when new moons are discovered orbiting Jupiter?

Astronomers are often discovering and reporting new moons of Jupiter. Once reported, these moons are given a temporary designation by the International Astronomical Union. They are included in Jupiter's large moon count once their orbits are confirmed. Recent counts show 50 moons, not including the "temporary" moons.

Saturn's Moon - Enceladus

Astronomers are particularly interested in the moon Enceladus because it contains hydrogen in gas form, and that is one of the key ingredients for life. It is a little hard to tell whether there are any organisms on this moon because the hydrogen gas is in oceans that are below the moon's frozen crust. Hydrogen gas is an essential element in supporting ocean life here on Earth, so scientists think that the conditions for life could actually be there. Astronomers also believe that Titan may be capable of harboring (or has in the past harbored) life as well; it is the only body (that we yet know of) in our solar system (other than Earth) that is home to a stable liquid. Cassini supplied much of the imagery and information scientists used to explore the possibility of life on Saturn's moons. However, they are going to need a lot more evidence to prove their case. For now, scientists have zoned in on Enceladus as the most likely home to life outside of Earth, and are experimenting with various microorganisms found on Earth that are known to be able to survive in extreme conditions, similar to those on Saturn's moons. While we have often wondered if there was life on other planets, the aliens of our imagination might exist on one of the many moons in our solar system. Much of Cassini's data still has yet to be studied in depth, so it could be that though the spacecraft may have already communicated the most shocking find in human history—life in another world

Jupiter's Moons

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Jupiter's Motion

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Jupiter's Structure

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Lesson 1: Introducing Jupiter and Saturn

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Lesson 2: Jupiter's Composition

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Lesson 3: The Skies of Jupiter

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Lesson 4: Saturn's Composition

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Lesson 5: Skies of Saturn

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Saturn's Motion

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Saturn rings all move at the same speeds True or False?

False; Each ring orbits the planet at a different speed from the others.

Jupiter's moon Ganymede

Ganymede is the largest planetary moon (larger than the planet Mercury) and the only moon in the solar system known to have its own magnetic field. Ganymede, along with Callisto, may also have an icy ocean beneath their crust. Etymology: Jupiter was at least an equal opportunity offender when it came to beautiful youths: Ganymede, the most beautiful mortal ever born, was a mere boy tending sheep when Zeus kidnapped him (taking the form of eagle this time). Unlike Zeus's female lovers, however, he suffered less from Hera's wrath, ultimately becoming the cupbearer of the gods and possibly being turned into the constellation Aquarius.

Jupiter's moon Callisto

Ganymede, along with Callisto, may also have an icy ocean beneath their crust. Etymology: You can probably guess by now that Callisto was a beautiful woman (a nymph, to be specific) whom the king of the gods took advantage of. Callisto was turned into a bear by Hera and was almost killed by her own son. She was ultimately saved at the last moment by being turned into the constellation Ursa Major.

How do we know so much of Saturn's rings?

Images and instrumental observations of the ring system provided by NASA's Voyager missions in 1980 and 1981 helped us define the rings and understand their composition better. Information from NASA's Cassini mission will help reveal how they formed, how they maintain their orbit and, above all, why they are there in the first place.

More of Saturns unique moons

In addition to Titan, Saturn has at least 53 natural orbiting satellites (as well as 9 provisional moons), and each of these moons is unique in its own way. Janus and Epimetheus, for example, sometimes pass so close to each other that they exchange orbits! Iapetus has one side that is very bright (like snow on a sunny day) and one side that is very dark (like black velvet). The moon Mimas has a large crater in it from an impact with some other item in space that almost broke the moon apart. There are also 16 moons that always keep the same side or face to Saturn as they orbit around the planet. This is known as "tidal locking," and it also happens with our Moon here on Earth.

how large are the outer planets?

In general, the outer planets are quite large, making up 99 percent of the mass of the celestial bodies orbiting our Sun.

Effects of Jupiter's Gravitational force

In the 1990s, scientists observed the strength and power of Jupiter's gravity. Jupiter's gravitational pull ripped apart a comet and pulled its pieces into an orbit around the planet. Eventually these pieces would be pulled even closer toward the surface of Jupiter. These broken pieces were as large as 2 km (1.2 miles) in diameter and were speeding towards the surface at 60 km/s (37 mi/s). And this isn't the only effect that Jupiter's gravity has had. Scientists in France and California have run simulations based on the effects of Jupiter's gravitational forces on the planet Mercury, which already has a strange orbit as it is. When Mercury reaches part of its orbit, it may possibly be pulled, pushed, or changed in another direction based on Jupiter's gravity. The scientists arrived at four possible outcomes in terms of how these forces could affect Mercury in the future: Sunburn: Mercury's orbit may cause it to crash into the Sun itself. The Lonely Planet: Mercury might be tossed out of the solar system entirely. Venus: Mercury might end up on a collision course with its neighbor Venus. Disaster!: Mercury might even collide with our Earth! However, it is unlikely that any of these scenarios will actually end up happening because the scientists also concluded that in order for any of these events to come to fruition, it would take billions and billions of years. This isn't a problem for the estimated survival of the universe, as it should still be around at that time, but it is a problem for the development of our solar system; scientists believe that our Sun will most likely grow to a red giant in about 5 billion years and swallow up all of the planets in the solar system as it expands. Good news for Mercury's alleged crash course with other planets but not such good news for planets long-term.

How did astronomers find out about Jupiter's moons?

In the year 1610, astronomer Galileo Galilee used a primitive telescope and discovered four smaller 'stars' near Jupiter. We now know these 'stars' as Jupiter's four largest moons: Io, Europa, Ganymede, and Callisto. These four moons are known today as the Galilean satellites.

Saturn's Centrifugal Force and its affects on gravity

Interestingly enough, Saturn has a decently strong centrifugal force—that is the force that acts outward on a body moving around a center from its own inertia. Because of this centrifugal force, you would actually weigh less if you could "stand" on the surface of the planet at its equator. Because of the powerful rotation Saturn has, the centrifugal force is strong enough to counteract some of the gravitational pull. Something that was 100 pounds on Earth would feel like 91 pounds on Saturn's equator rather than 107 pounds at Saturn's poles—both north and south. (This actually happens here on Earth too. Something weighing 100 pounds at Earth's poles actually weighs 99.8 pounds at the equator.)

Which of the outer planets are the largest and what are these planets composed of?

Jupiter and Saturn are the largest of the outer planets and are mainly composed of helium and hydrogen gas. (Jupiter is bigger)

Jupiter's Rotation

Jupiter completes a rotation on its axis in slightly fewer than 10 hours, making it the fastest rotating of all the planets. This fast rotation creates an equatorial bulge easily seen through an Earth-based, amateur telescope. Jupiter is not a solid body, so its upper atmosphere rotates differently, taking about five minutes longer than the equatorial atmosphere.

Jupiter's Ring System

Jupiter has a "faint" ring system. The rings seem to be made of dust, which is different from the ice rings of Saturn. The ring system has four parts: an inner "halo ring," a main ring, and two gossamer rings. The rings appear to have a reddish color, except for the halo ring which is blue in color. In a surprise discovery in 1979, NASA's Voyager discovered that Jupiter's rings are comprised of a flattened main ring and an inner, cloud-like ring, which is called the halo and is composed of dark, small particles. A third, transparent ring, known as the gossamer ring, is actually three rings of microscopic debris from three small moons: Adrastea, Amalthea, and Thebe. Data obtained from the Galileo mission indicates that Jupiter's ring system may have been formed by dust kicked up from meteoroids smashing into the four small inner moons. Jupiter's rings have been captured by the Hubble Space Telescope.

Jupiters composition and potential core

Jupiter is composed mainly of gas and liquids. Like the other gas planets, Jupiter does not have a solid surface. However, its materials do grow denser the closer they are to the core of the planet. Astronomers and scientists believe that Jupiter may have a core of rock that could be as large as Earth. The presence of a core and the theories regarding its composition are based on models of planetary formation and gravitational measurements. The core is thought to be surrounded by a layer of metallic hydrogen. The atmosphere is then above this. Both the temperature and pressure increase in the direction of the core.

Jupiter's Appearance (Red Spots)

Jupiter's beautiful appearance is the result of clouds composed of ammonia. Water vapor exists below the clouds and is sometimes visible when looking through clear spots in the clouds. The planet's signature dark and light "stripes" are created by strong east-west winds in its upper atmosphere. The famous Great Red Spot is actually a giant storm that has been observed since the 1800s. This storm is large enough that it would fit two or three planets the size of Earth within it! The more recent "Little Red Spot" is comprised of three smaller storms and is about half the size of the Great Red Spot.

Jupiter's Orbit and Tilt (Seasons)

Jupiter's elliptical orbit is inclined 1.31°, and the axial tilt of Jupiter is relatively small (3.13°). As a result, Jupiter does not have significant seasonal changes as Earth and Mars do.

Jupiter's Moon Io

Jupiter's moon Io is the most volcanically active body in our solar system. Etymology: Io was one of the lovers of Jupiter (or Zeus, to the Greeks) and suffered greatly for it (Zeus's wife Hera, or Juno for the Romans, was jealous of his mortal lovers and tortured them in many ways). After spending years as a cow that was continually stung by a gadfly and forced to roam the world, she eventually had her humanity returned to her and became the ancestor to many Greek heroes, including Hercules.

what are the Gas Giants (Jovian Planets)?

Jupiter, Saturn, Uranus, Neptune; They are also referred to as the Jovian planets because of the characteristics they share with the planet Jupiter

Jupiter's Gravitational force

Jupiter, being much more massive than Earth, also has stronger gravity—2.5 times stronger! Jupiter's gravity is 24.79 m/s2. To put that more into perspective, a person weighing 155 pounds on Earth would feel like they weighed a whopping 391 pounds on Jupiter (although we will never experience that because of the incredible strong winds and the fact that Jupiter does not have a solid surface to even stand on).; In comparison, Earth's gravitational force is 9.8 m/s^2

How and when did astronomers first study the Galilean satellites?

NASA's Galileo mission (1985-2003) provided scientists here on Earth with valuable data about Jupiter and its moons.

Mission Juno, its purpose and findings

On August 5, 2011, NASA launched Juno, a spacecraft that conducts in-depth examinations of Jupiter's chemistry, atmosphere, interior structure, and magnetosphere. Named after the Roman mythological wife of Jupiter, the god of the sky, the goddess Juno was able to peer through the clouds and reveal Jupiter's true nature. Since arriving at Jupiter in 2016, Juno has measured the amount of water and ammonia in its atmosphere. One of the questions astronomers hope to answer is whether or not the planet actually has a solid core. However, once Juno began sending back data from its mission, it became clear that the planet was more complicated than astronomers thought. While they knew it was made of gases, they did not realize how complex the movement of these gases are. Now they know that these gases have currents, like our oceans. As Juno continues to orbit the planet and send information back, astronomers will gain a better understanding of it. Jupiter is a particularly important planet to study because its gigantic mass allows Jupiter to hold onto its original composition. This provides us with valuable insight into our solar system's history.

Saturn's Gravity (Weight on Saturn)

Remember, Earth's gravitational pull is 9.8 m/s2. Jupiter's gravity is equal to 24.79 m/s2. But Saturn's gravity is 10.44 m/s2. This is because Saturn is a gas giant and has a low density. If both Jupiter and Saturn had solid surfaces, their gravitational pull would be exceedingly greater. The difference in gravity between Earth and Saturn is just about 107 percent. This means that if you weighed 100 pounds on Earth you would weigh 107 pounds on Saturn. If you weighed 155 pounds on Earth, you would feel like you only gained 10 pounds and weigh about 165 pounds on Saturn.

Saturn's Day (Rotation)

Saturn has a rotational period itself of about 10 to 11 Earth hours.

Saturn's Shape

Saturn has a rotational period itself of about 10 to 11 Earth hours. This rapid rotation affects Saturn's shape, flattening out Saturn at its poles by about 10 percent. This helps make Saturn an oblate spheroid, or more elliptically shaped rather than round. Because of this shape, the visible features of Saturn rotate at different rates. System 1, for example, which encompasses the equatorial part of Saturn, rotates at around 10 hours, 14 minutes, and 0 seconds. System II, which represents the parts north and south of the equatorial zones, rotates at around 10 hours, 38 minutes, and 25.4 seconds.

Saturn's Year (Orbit)

Saturn takes about 10,759 Earth days to complete one revolution around the Sun at an average speed of 9.69 km/s (6 mi/s).

What could be causing Saturn's magnetic field

Saturn's metallic hydrogen layer is believed to support an electrical current, thus turning the planet into a giant electromagnet! Meanwhile, astronomers theorize that the high heat is caused when helium falls as rain, generating heat through atmospheric friction and forming a hot shell around the core.

Gas Giants rings discoveries

Saturn's rings remained a unique feature in our solar system until rings were discovered around Uranus in 1977. Interestingly, soon after, rings were discovered around Jupiter and Neptune as well.

Jupiter's average distance from the sun

The average distance between Jupiter and the Sun is 778 million kilometers (483 million miles or about 5.2 times the average distance from Earth to the Sun, or 5.2 AU)

Jupiter's magnetic field

The combination of gases and liquids on Jupiter also produce a strong magnetic field. Underneath the clouds on its surface is an enormous ocean of liquid hydrogen. On Earth, hydrogen is a gas; however, it is liquid on Jupiter due to the pressure in Jupiter's atmosphere. The quick rotation causes this hydrogen to swirl, creating the strongest magnetic field in our solar system.

Jupiter's Atmosphere

The composition of Jupiter's atmosphere is similar to that of the Sun (mostly hydrogen and helium). If Jupiter had been about 80 times more massive, it probably would have become a star rather than a planet.

Saturn's average distance from the Sun

The distance between the Sun and Saturn averages about 1.4 billion kilometers (8.7 million miles); this is about twice the distance between the Sun and Jupiter. During its revolution, the distance of Saturn to the Sun varies by up to 155 million kilometers (96 million miles) because of Saturn's orbital path.

How large is Jupiter in relation to the solar system?

The largest and most massive of the planets, Jupiter alone accounts for 2.5 times as much mass as all of the other planets in the solar system.

Jupiter's Shape

The planet is shaped as an oblate spheroid, which means that the diameter across its equator is longer than the diameter when measured between its two poles.

How are Saturn's rings classified/named?

The rings of Saturn are given a letter name in the order of their discovery. Working outward from the planet, the main rings are known as C, B, and A. The largest gap in the rings separates B and A and is known as the Cassini Division. Many fainter rings have been discovered more recently, including the faint D ring that is closest to the planet, and the F, G, and E rings.The structure of the rings is believed to be related to the gravitation of Saturn's many moons, yet still, much of it remains unexplained.

Saturn's moon - Titan

Titan, Saturn's giant moon, has a thick atmosphere that's regarded by scientists as one of the most complex chemical environments in our solar system. Its atmosphere continuously produces hydrocarbons that rain down the moon's icy surface, cloaking it in soot and forming liquid methane and ethane lakes. Because it's continuously destroyed by sunlight and converted to more complex molecules and particles, the methane gas which creates this atmospheric environment should not last for long. Research from NASA-funded scientists indicates Titan's atmosphere developed long after the satellite was formed and estimates the methane age from the atmosphere itself at fewer than one billion years. To put it into perspective, our planet Earth is 4.5 billion years old. Titan is extremely cold, with a surface temperature of -290° F (-180° C) and is home to some interesting bodies of water; the lakes and rivers on Titan are thought to contain not water but a mixture of methane and ethane that has more of an oily texture than water does. In fact, NASA has even discussed constructing a space-faring submarine to investigate these lakes and rivers.

(Roman Naming) The planet Jupiter was named after the Roman god of the sky and king of the gods True or False?

True

Saturn has the Slowest wind speeds in the Solar System? True or False

True; Even if you were able to stand on the gaseous surface of Saturn, you might be blown away by the wind. Saturn is the windy planet. Wind speeds have been clocked at a staggering 1800 kilometers per hour—which is over 1,118 miles per hour—at the equator. (Neptune has the strongest winds btw 2000kph and the fastest wind speed ever recorded by scientists on Earth was 511 kilometers per hour (318 mph))

Saturn's Surface

Try standing on the surface of Saturn and you'd be standing in gas. The planet Saturn is a giant planet of gas, mostly hydrogen and helium. Saturn may have a solid core, but its exterior lacks a definite shape because of its gaseous composition. Deep down in the depths of the body of Saturn, where the hydrogen gas is under tremendous pressure, it is transformed into liquid metallic hydrogen. A solid rock core is believed to exist in the center. Saturn radiates more energy into space than it receives from the Sun. Scientific planetary models suggest that Saturn's core is probably small and rocky, surrounded by helium, hydrogen, and small amounts of volatiles. French astronomers Didier Saumon and Tristan Guillot estimated in 2004 that the interior core of Saturn is about 9 to 22 times the mass of Earth. The interior of Saturn is estimated to be over 21,000° F (11,700° C). This high heat is enough to transition the hydrogen in the interior to a metal so the core is thought to be surrounded by a metallic hydrogen layer. A liquid layer of helium and hydrogen follows, transitioning to a gas as the distance from the core grows.

What are the outer planets made of?

Unlike the terrestrial inner planets, which are made of rock and metal, the gas planets do not have solid surfaces. The outer planets' gaseous material gets denser with depth so that what we see when we look at these planets are really the tops of clouds of gas in their atmospheres.

Saturn's rings size

While the other three gas planets in the solar system also have rings orbiting around them, Saturn's rings are by far the largest, boasting a thickness of about one kilometer (3,200 feet) or less and spanning up to 282,000 kilometers (175,000 miles), which is about three-quarters of the distance between Earth and its Moon!

Saturn's Troposphere (the part of the atmosphere where weather occurs)

can be divided into three regions where clouds of a particular kind, called "cloud decks," are found. The location of the clouds is based on the temperature point at which condensation of vapors occurs. The visible, top cloud deck is 100 kilometers (62 miles) below the top of the troposphere in a region known as the tropopause. It contains the ammonia clouds that give the planet its yellow color. Below that (about 170 kilometers, or 106 miles, below the troposphere) lies the second deck made of ammonium hydrosulphide clouds. And below that, where temperatures are a balmy 32° F (0° C), is the bottom deck where you will find clouds of water.

Jupiter's year

it completes an orbit every 11.86 years

Why is Saturn not as colorful as Jupiter? (Probably)

probably due to sulfur content

Saturn's atmosphere composition

the planet's atmosphere is mainly comprised of molecular hydrogen (96.3 percent) and helium (3.25 percent). The remaining less than half of 1 percent is composed of small amounts of acetylene, ammonia, phosphine, methane, and ethane.