How Many Moons Does the Planet Uranus Have and When Were the Moons Orbiting Uranus Discovered?

How Many Moons Does the Planet Uranus Have and How Did the Moons Orbiting Uranus Get Their Names? Before the space age, we knew of five satellites orbiting Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. The names came from the works of Shakespeare and the poet Alexander Pope. Ten more moons, discovered by the spacecraft … Read more

How Cold Is the Planet Uranus and What Effects Does Uranus’s Cold Temperature Have On Its Atmosphere?

Voyager 2 registered a nearly consistent temperature of –155°F (-221°C) on Uranus. Strong winds, up to 180 miles (288 km) per hour, that blow in the same direction as Uranus rotates keep the temperature steady all around the planet. The cold is responsible for our inability to see any surface detail on this pale blue … Read more

What Is Saturn’s Great White Spot and How Often Does the Great White Spot On Saturn Appear?

Similar to Jupiter’s Great Red Spot, a white spot on Saturn reveals the presence of a huge atmospheric storm. Unlike Jupiter’s ever-present spot, Saturn’s white spot appears only periodically, approximately every 30 years. First identified in 1876, the spot has appeared more or less on schedule ever since. It is located near the equator and … Read more

Who Discovered Saturn’s Biggest Moon Titan, How Did Titan Get Its Name, and What Is Titan Made of?

Titan was discovered in 1655 by the Dutch astronomer Christiaan Huygens. The moon’s name came from John Herschel, son of William Herschel, discoverer of Mimas and Enceladus, in 1847, and was inspired by the names of the mythological Titans, sisters and brothers of Cronos, the Greek Saturn. Saturn’s largest and brightest moon, Titan, seems to … Read more

When Was Uranus Discovered, How Did the Planet Uranus Get Its Name, and What Does Uranus Mean In Greek?

William Herschel (1738-1822) was a musician who began to study the mathematical foundation of harmony. Mathematics led him to astronomy, and, with the help of his sister, Caroline, Herschel set out to map every star in the northern hemisphere with a magnitude of 4 or greater. Through his detailed and methodical observations, Herschel found and … Read more

How Is the Planet Uranus’s Rotation Tilted On Its Axis and What Does a Retrograde Rotation Mean?

The planet Uranus’s axis is tilted in a peculiar way. Earth’s axis tilts at 23.5°; Uranus’s axis tilts at 97.9°, which is at more than a right (90°) angle. Imagine Earth’s poles being located near the equator. The planet, however, still rotates around its north-south axis. Because it is tilted more than 90°, Uranus’s rotation … Read more

Why Are There Gaps Between the Rings Around Saturn and What Are the Divisions In the Ring System Called?

The two most prominent divisions in Saturn’s ring system are the Cassini division and the Encke division, named after their discoverers. The Cassini division extends for 2,100 miles (3,360 km) between rings A and B. The 200-mile (320-km) Encke division lies within ring A. These divisions appear to be gaps between rings, allowing us to … Read more

What Are the Different Types of Rings Around Saturn Called and Why Do Eccentric Rings Have Elliptical Orbits?

Idiosyncratic rings around the planet Saturn are rare and, for the most part, inexplicable. They do not conform to the laws of physics as we understand them. The primary rings, A through G, orbit Saturn in circles. According to physics, it should be impossible for a ring to do otherwise, to have an elliptical, or … Read more

What Is Saturn Made of and How Is Saturn’s Composition of Hydrogen and Helium Similar To the Planet Jupiter?

Within the rings lies the second largest planet in the solar system, Saturn. Its composition is similar to that of its next-door neighbor, Jupiter, mostly hydrogen and helium gases. The planet’s ice-covered core of iron and silica is just a little bit bigger than Earth. Compressed hydrogen around the core resembles a metal, and is … Read more

How Hot Is the Planet Saturn and How Much Heat Does Saturn Generate By Slow Gravitational Compression?

The planet Saturn generates more heat than it receives from the Sun. It has lost the heat caused by its formation, but helium drops “rain” down from the atmosphere, mostly hydrogen, which creates heat. The droplets of helium releasing heat by friction as they fall down through the lighter hydrogen. The cloud-top temperature ranges around … Read more

How Do We Know What Saturn’s Core Rotation Period Is and How Strong Is Saturn’s Magnetic Field?

The planet Saturn has a very strong magnetic field. Spacecraft sent to study the planet recorded regularly pulsing radio waves to determine the core’s rotational speed. The magnetic field on Saturn is at least 500 times, some say 1,000 times, stronger than Earth’s magnetic field. Saturn’s magnetic poles are almost exactly aligned with its geographic … Read more

How Large Are the Rings Around the Planet Saturn and How Far From the Surface of Saturn Do the Rings Extend?

The whole system of rings, gaps and all, begins about 40,000 miles (64,000 km) out from Saturn’s equator and ends 290,000 miles (464,000 km) from the surface. That’s 250,000 miles (400,000 km) of rings and gaps. The particles are not spread out on a single plane, but the rings are very thin. Compared to the … Read more

How Do Saturn’s Planetary Rings Orbit Saturn and Which Of Saturn’s Rings Revolve Around the Planet the Fastest?

Saturn’s rings have circular orbits, but they revolve at various speeds. Parts of a single ring even orbit Saturn at different rates. For instance, the outer edge of ring E, furthest from the planet, has an orbital period of 4 hours, but the inner edge, some 180,000 miles (288,000 km closer) takes 22 hours to … Read more

How Fast Do Jupiter’s Moons Orbit the Planet and What Is the Difference In Orbital Period Between the Moons?

Astronomers frequently use orbital period, or how long one revolution takes, to measure speed instead of miles, or kilometers per hour. The three families of satellites are clustered by period as well as distance. Of the four closest moons, none takes more than 1 day to orbit Jupiter. The four Galilean moons, also in the … Read more

Who Discovered Jupiter’s Largest Moon Ganymede, What Is Ganymede Made of, and How Did It Get Its Name?

Galileo Galilei was the first astronomer to observe Jupiter’s moon Ganymede on January 7, 1610. Ganymede, made mostly of ice and rock, is the third farthest Galilean moon from Jupiter and is the planet’s largest satellite. Ganymede is also the biggest moon, or satellite in our solar system. Its surface is cratered, like Jupiter’s farthest … Read more

When Was Jupiter’s Sixth Moon Europa Discovered, How Did Europa Get Its Name, and What Is It Made Of?

Jupiter’s sixth moon Europa was discovered in 1610 by Galileo Galilei, and is named after a mythical Phoenician noblewoman, Europa, who was courted by Zeus and became the queen of Crete. The Galilean moon Europa orbits Jupiter between Io and Ganymede. Europa is about the same size as Earth’s moon. It has a surface of … Read more

Who Discovered Jupiter’s Second Largest Moon Callisto and What Is Callisto Made Of?

The third-largest moon in the Solar System Callisto was discovered in 1610 by Galileo Galilei. The farthest Galilean moon from Jupiter, Callisto is mostly made of ice and rock. Its surface shows many craters, but unlike our Moon craters, these are rather shallow with low walls encircling them. Callisto’s craters were probably partially filled in … Read more

What Is Jupiter’s Moon Io Like and Why Does Io Have So Much Volcanic Activity On Its Surface?

Rocky Io is the closest Galilean moon to Jupiter. The craters that mark its surface are volcanic craters, not the result of meteorite bombardment. The tallest volcanoes are about 5.5 miles (8.8 km) high. Instead of molten rock, sulfur compounds spew out of Io’s volcanoes, covering evidence of any impact craters and giving the moon … Read more

What Is the Great Red Spot On the Planet Jupiter and When Was the Great Red Spot On Jupiter First Discovered?

Since the seventeenth century, observers have seen a huge, oval red spot south of Jupiter’s equator. The Great Red Spot has a greater surface area than Earth: 8,400 miles (13,440 km) wide by 24,000 miles (38,400 km) long. Scientists have determined that the spot is a huge atmospheric storm. It appears as a hollow, or … Read more

Is Jupiter’s Great Red Spot Always In the Same Place and Is the Great Red Spot On Jupiter Visible From Earth?

One of the best known features of the planet Jupiter is the Great Red Spot. The Great Red Spot is a permanent anticyclonic storm, and is significantly larger than the Earth. The spot on Jupiter usually can be found 22° south of the equator, in or near the South Equatorial Belt. It rotates counterclockwise, with … Read more

How Far Away From Jupiter Do the Moons Orbit and How Many Different Groups Of Moons Orbit Jupiter?

Jupiter’s sixteen known moons travel in three distinct groups. The first, including the four Galilean moons, ranges from 77,000 miles (124,000 km) to over 600,000 miles (960,000 km). The next group orbits from 6.6 million miles (10.56 million km) to almost 7.2 million miles (11.52 million km) away. The third family of satellites is almost … Read more

How Hot Is the Planet Jupiter and and What Is the Temperature Of Jupiter’s Core?

Although Jupiter is a great distance from the Sun, it is a relatively hot planet. Scientists have discovered that almost twice as much heat radiates from the planet’s rocky core than is received from the Sun. The core’s exact temperature is unknown, but it is probably around 30,000°K (53,500°F/30,000°C). Jupiter continues, from the time of … Read more

What Color Is the Planet Jupiter and What Causes the Different Colors Of the Cloud Bands On the Planet Jupiter?

Jupiter’s primary gases, hydrogen and helium, are colorless. Trace chemicals within the planet’s gas layers, such as methane, ammonia, and phosphine, are responsible for the colors of the belts and zones. The colors range from cream and yellow through pink, orange, and brown to brick red. Brighter areas suggest hotter temperatures, and darker areas, cooler … Read more

How Many Moons Does Jupiter Have and What Is the Biggest Moon That Orbits the Planet Jupiter?

Jupiter has sixteen known satellites, but astronomers believe there could be more. The discovery of the four largest, Ganymede, Callisto, Io, and Europa, is credited to Galileo, who recorded them in 1610. The average diameter of the Galilean moons measures 2,540 miles (4,230 km), whereas the average diameter of the other Jovian moons is a … Read more

What Are the Outer Planets In the Solar System and What Are the Characteristics Of the Five Outer Planets?

Size and composition are the two major characteristics shared by Jupiter, Saturn, Uranus, and Neptune. The smallest outer planet, with the exception of Pluto, which is in a category by itself, is Neptune, and Neptune is almost four times larger than Earth. The outer planets have small cores and huge gaseous outer surfaces. When the … Read more

What Is the Planet Jupiter Made Of and What Gases Make Up Jupiter’s Atmosphere and Core?

According to current speculation, Jupiter probably has a small, solid core of silica. Above that lies a shell of a different form of liquid hydrogen. Jupiter’s core is surrounded by dense metallic hydrogen, which extends outward to about 78 percent of the radius of the planet. Droplets of helium and neon precipitate downward through this … Read more

What Are the Different Bands of Clouds That Appear Across Jupiter and How Are the Bands On Jupiter Formed?

Some eighteen zones and belts can be identified by their different colors, brightness, spots, and rotation periods. Zones are dark bands; belts are bright bands. The main two are the North Equatorial Belt, at approximately 7° to 20° latitude, and the South Equatorial Belt, at approximately –7° to –21° latitude. Both change in width, with … Read more

How Do We Know If There Is Life On Mars and Why Did Percival Lowell Believe That Martians Built Canals On Mars?

Experiments on Earth have concluded that certain cells can survive a simulated Martian environment. In 1996, a meteorite that originated on Mars was discovered. The announcement that this rock contained possible evidence of life on Mars or evidence that life once existed on Mars, has sped up plans to send missions back there. Remember, however, … Read more

What Are the Outer Planets, What Are The Names of the Outer Planets, and Where Are the Outer Planets Located?

The planets that orbit the Sun beyond the asteroid belt in our solar system are known as the outer planets. Besides their location, they share many other similarities, except for Pluto, which is a highly unusual planet. Jupiter, Saturn, Uranus, and Neptune are all much larger than Earth and are made mostly of gas. This … Read more

What Is the Atmosphere On Mars Like and How Much Carbon Dioxide Is There On the Planet Mars?

The atmosphere on Mars is relatively weak. It is so thin that damaging ultraviolet solar radiation makes its way unimpeded to the planet’s surface. Carbon dioxide makes up 95 percent of the atmosphere, followed by nitrogen (2.7 percent) and argon (1.6 percent). Oxygen, water vapor, neon, krypton, xenon, and ozone comprise less than 1 percent … Read more

What Is the Tallest Mountain and Volcano In the Solar System and Is There Still Volcanic Activity On Mars?

Mons Olympus, the tallest known volcano, and mountain, in the solar system, is one of many large volcanoes on Mars. Mons Olympus is about 27 km tall, and can be found in the vast upland region Tharsis, which contains several other large volcanoes. Mons Olympus is Latin for “Mount Olympus”, and is believed to have … Read more

How Much Water Is There On Mars and What Are the Most Prominent Features on the Surface of the Planet Mars?

Evidence of water has fed scientific debates on the possibility of life on Mars for centuries. A well-known twentieth-century astronomer, Percival Lowell, spent his career mapping what he believed were irrigation canals built by Martians. His findings have been proven false, but there are dry channels on Mars that look like they were created by … Read more

Is the Southern Hemisphere On Mars Older Than the Northern Hemisphere and What Happened To the Craters There?

More craters are found in the southern hemisphere on Mars. This makes astronomers think that the surface there is older than in the northern hemisphere. Something happened in the north, perhaps volcanic activity or water erosion, to cause craters to disappear. There is further evidence supporting the astronomers’ theory: the surface of the northern hemisphere … Read more

Why Is the Orbit of Mars Around the Sun Not a Perfect Circle and How Long Does Mars Take To Orbit the Sun?

No planet has a truly circular orbit around the Sun. Mars’s orbit is particularly elongated, which affects the planet’s seasons. Mars takes 788 Earth days to orbit the Sun. At its farthest (aphelion), it is about 155 million miles (250 million km) from the Sun. At its closest (perihelion), Mars is some 130 million miles … Read more

What Effect Does Summer Have On Mars and How Do the Ice Caps Cause Dust Storms On the Planet Mars?

Summer in the southern hemisphere causes the most weather activity on Mars. The temperature increase shrinks the southern polar ice cap, at the same time, the northern ice cap, experiencing winter, grows larger, which increases the air pressure. Increased air pressure causes severe winds to blow toward the equator. The winds can reach up to … Read more

What Is Winter Like on Mars and How Low Do Temperatures Get On the Planet Mars During the Winter Season?

During winter in the southern hemisphere on Mars, the polar ice cap grows to cover almost one-quarter of the planet. At the same time, during summer in the northern hemisphere, the northern ice cap is shrinking. Temperatures on Mars can reach as low as –190°F (-123°C). Sometimes a frost consisting of water and dust covers … Read more

Why Aren’t There Many Impact Craters On the Planet Venus and Why Do Most Small Asteroids Burn Up?

If all those planetesimals and asteroids were flying around some 4 billion years ago, colliding, accreting, and taking chunks out of planets, why don’t we see much evidence of them on Venus? Asteroids probably did hit Venus as much as any other planet; they just didn’t leave behind much visible evidence. Venus’s atmosphere would have … Read more

Why Is the Planet Venus Covered In Clouds and How Were the Clouds On Venus Formed From Sulfur Dioxide?

On Earth, clouds are created through water evaporation and condensation. The clouds are water-based. Venus’s clouds are made by a process called photochemistry, whereby the Sun’s ultraviolet rays react with chemicals in Venus’s atmosphere. The clouds around Venus have an acid base, sulfur dioxide. On Earth, sulfur dioxide is released during volcanic activity. It’s what … Read more

How Hot Is the Planet Venus and Why Is Venus Known As the Hottest Planet In the Solar System?

The Planet Venus is very hot indeed. The surface temperature averages almost 900°F (480°C) around the whole planet. This extreme heat results from the greenhouse effect, which occurs when infrared, or heat-producing rays from the Sun enter an atmosphere and cannot get back out. Carbon dioxide, which makes up 96.5 percent of Venus’s atmosphere, lets … Read more

What Is the Atmosphere On the Planet Venus Made Of and Why Is Venus Permanently Covered By Dense Cloud?

The planet Venus has an extremely dense atmosphere. The atmosphere on Venus, the second planet from the Sun, consists primarily of carbon dioxide (96.5 precent). Nitrogen makes up 3.5 percent of the atmosphere. Traces of gases such as sulfur dioxide, carbon monoxide, hydrochloric acid, and oxygen (0.00003 percent) have also been detected. The atmospheric mass … Read more

How Did the Planet Venus Get Its Name and What Does Venus Mean In Latin?

The Romans who derived their religious pantheon from the Greek tradition, named the planet Venus after their goddess of love. On Venus, all topographical features except one are named for women, Venus being a goddess of womanhood. For instance, the main craters include Anna Pavlova (1881-1931), the prima ballerina of her lifetime; Sacajewea (c. 1789-1812), … Read more

What Effect Does the Atmosphere Have On the Planet Venus and Why Is Venus Hotter Than Mercury?

The two major results of Venus’s atmosphere are the amount of pressure it exerts on the planet’s surface and the heat it traps. Carbon dioxide is a heavier gas than nitrogen. Because the atmosphere is more than 96 percent carbon dioxide, the pressure is ninety times greater on Venus than on Earth. Without state-of-the-art, space-age … Read more

How Did Land Form On Other Planets In the Solar System and How Do We Find Evidence of Volcanic Activity?

We look at the way land, terra in Latin, was formed on Earth to understand how the surfaces of other terrestrial planets evolved. Volcanoes created most of Earth’s terrain. Molten material from Earth’s mantle bubbled up 4 billion years ago to form the first continents. On Mercury, land ridges provide evidence of extreme volcanic activity … Read more

How Hot Does the Planet Mercury Get and Does the Planet Mercury Have an Atmosphere?

The planet Mercury is too small for its gravity to retain any significant atmosphere over an extended period of time. However, Mercury does have a “tenuous surface-bounded exosphere” containing hydrogen, helium, oxygen, potassium, and other elements. The hydrogen and helium that make up Mercury’s very thin atmosphere don’t actually originate on the planet. The gases … Read more

How Do Astronomers Know So Many Details About Mercury and When Did the First Spacecraft Visit Mercury?

Just looking at the planet Mercury doesn’t give astronomers very much information. Fortunately, electromagnetic waves, mostly radio waves, from Mercury are picked up around the world. They have helped establish the topography and composition of Mercury. Also, twice in 1974 and once in 1975, the spacecraft Mariner flew by Mercury and photographed as much of … Read more

When Was the Planet Mercury First Discovered, How Did It Get Its Name, and What Does Mercury Mean In Latin?

The earliest known recorded observations of Mercury are from the Mul.Apin tablets around the 14th century BC. The ancient Greeks called the planet Στίλβων (Stilbon), which means “the gleaming”. The Romans named the planet Mercury after the swift-footed Roman messenger god, Mercury, or Mercurius in Latin. Mercury is the smallest planet in the solar system … Read more

Why Are There So Many Impact Craters On the Planet Mercury and How Many Surface Craters Does Mercury Have?

The planet Mercury seems to have been hit by a lot of asteroids. Just under 50 percent of Mercury’s surface has been photographed by spacecraft. The photos show an average of one hundred to one thousand 6-mile (10-km) craters per each 600,000 square miles, or 1 million square kilometers. The appearance of so many craters, … Read more

What Is the Largest Crater Photographed On the Planet Mercury and Who Was the Crater Named After?

The largest crater photographed so far has been named Beethoven, after the famous composer Ludwig van Beethoven. Mercury’s topographic features are named for famous people, such as Shakespeare and Michelangelo; exploration ships, including the Santa Maria; radar installations, such as the Russian (Soviet) Vostok; and other gods, such as the Scandinavian king of gods, Odin. … Read more

What Is the Most Obvious Physical Feature On the Planet Mercury and How Many Impact Craters Does Mercury Have?

What Is the Most Obvious Physical Feature On the Planet Mercury and How Many Impact Craters Does Mercury Have? The largest topographic feature seen on Mercury is the Carolis Basin, a depression as wide as Texas about 800 miles (1,280 km in diameter). It is bordered on one side by tall mountains, called scarps, which … Read more