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ASTRONOMY SOLAR SYSTEM GALAXIES ABSOLUTE ZERO ASTROBIOLOGY
ESCAPE VELOCITY SATELLITE METEROIDS KUIPER BELT STARS
SUN MOON MARS MERCURY VENUS
SATURN NEPTUNE JUPITER NEBULA BEYOND THE SOLAR SYSTEM

ASTRONOMY

UNIVERSE
Universe means all existing things i.e. the whole creation. The branch of the science that deals with the study of universe is called astronomy. The universe consist of , the solar system, Stars, Galaxies

SOLAR SYSTEM

The part of the universe in which the sun occupies the central position of the system holding together all the heavenly bodies that revolve around it, is called solar systems.

The solar systems consists of nine planets. They are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

What is the solar system?
The solar system is the sun and everything that orbits around it. It includes the nine planets and their moons, numerous asteroids and comets. These are all held in orbit around the sun by the sun's strong gravity.
What is the order of the planets in the solar system?
Our solar system has nine planets which orbit the sun. In order of distance from the sun they are; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
Why are all of the planets round?
All of the planets are round because of gravity. When our solar system was forming, gravity gathered billions of pieces of gas and dust into clumps which grew larger and larger to become the planets. The force of the collision of these pieces caused the newly forming planets to become hot and molten. The force of gravity, pulled this molten material inwards towards the planet's center into the shape of a sphere. Later, when the planets cooled, they stayed spherical. Planets are not perfectly spherical because they also spin. The spinning force acts against gravity and causes many planets to bulge out more around their equators.
How many planets in the solar system have rings?
Four out of the nine planets in the solar system have rings. They are the four giant gas planets Jupiter, Saturn, Uranus and Neptune. Saturn, which has by far the largest ring system, was know to have rings for a long time. It was not until the 1970's that rings were discovered around the other gas planets. The rings around Jupiter, Uranus and Neptune are much smaller, darker and fainter than the rings of Saturn.
How did the planets get their names?
All of the planets, except for Earth, were named after Greek and Roman gods and godesses. Jupiter, Saturn, Mars, Venus and Mercury were given their names thousands of years ago. The other planets were not discovered until much later, when telescopes were invented. The tradition of naming the planets after Greek and Roman gods and goddesses was carried on for the last three planet discovered as well. Mercury was named after the Roman god of travel. Venus was named after the Roman goddess of love and beauty. Mars was the Roman god of War. Jupiter was the king of the Roman gods, and Saturn was the Roman god of agriculture. Uranus was named after an ancient Greek king of the gods. Neptune was the Roman god of the Sea and Pluto was the Roman god of the underworld. The name Earth is an English/German name which simply means the ground.
How do the planets stay in orbit around the sun?
The solar system was formed from a rotating cloud of gas and dust which spun around a newly forming star, our sun, at its center. The planets all formed from this spinning disk-shaped cloud, and continued this rotating course around the sun after they were formed. The gravity of the sun keeps the planets in their orbits. The stay in their orbits because there is no other force in the solar system which can stop them.
Are moons always smaller than planets?
Moons are always smaller than the planet that they orbit (move around). A smaller body always orbits around a larger body rather than the other way around because the larger body has more gravity. However, not all of the moons are smaller than all of the planets. There are seven moons in our solar system, including our own moon, that are larger than the planet Pluto. Jupiter's moon Ganymede, the largest moon in the Solar System, and Saturn's moon Titan are both larger than the planets Mercury and Pluto. Earth's moon, Jupiter's moons Callisto, Io, and Europa, and Neptune's moon Triton are all larger than Pluto, but smaller than Mercury.
Where is the highest mountain in our solar system?
The highest mountain and volcano in the solar system is on the planet Mars. It is called Olympus Mons and is 16 miles (24 kilometers) high which makes it about three times higher than Mt. Everest. In addition to being very tall, it is also very wide (340 miles or 550 kilometers) and covers an area larger than the entire chain of Hawaiian islands. Olympus Mons is a very flat mountain which slopes by only 2 to 5 degrees. It is a shield volcano built up by eruptions of lava.
Which planet spins the fastest?
Jupiter is the fastest spinning planet in our solar system rotating on average once in just under 10 hours. That is very fast especially considering how large Jupiter is. This means that Jupiter has the shortest days of all the planets in the solar system. Since Jupiter is a gas planet, it does not rotate as a solid sphere. Jupiter's equator rotates a bit faster than its polar regions at a speed of 28,273 miles/hour (about 43,000 kilometers/hour). Jupiter's day varies from 9 hours and 56 minutes around the poles to 9 hours and 50 minutes close to the equator.

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GALAXIES

A large group of stars is called galaxy. The galaxies are the building blocks of the universe. There are billions of galaxies having different sizes and regular and irregualer shapes. The shapes of regualer galaxies may be elliptical, spiral and barred spiral.

We belong to a galaxy called Milky way (Akash Ganga).



ABSOLUTE ZERO

What is absolute zero?
Absolute zero is the lowest temperature possible. At a temperature of absolute zero there is no motion and no heat. Absolute zero occurs at a temperature of 0 degrees Kelvin, or -273.15 degrees Celsius, or at -460 degrees Fahrenheit.

ASTROBIOLOGY

What is astrobiology?
Astrobiology is the study of life within the universe. Astrobiologists study how life forms and develops, and where life can be found. Astrobiology involves the search for life outside Earth, the study of planets and moons within our solar system, and the search for habitable planets around other stars. Astrobiologists also study life here on Earth (especially extreme life) to help them learn about the environments in which life can survive.
What is an astrobiologist?
An Astrobiologist is a person who studies the possibility of life beyond Earth. Astrobiologists try to understand how life originates and how life can survive in many different types of environments. This often involves the study of extreme life right here on Earth. They study different planets and moons to see if conditions there might support life. Some astrobiologist are involved in projects which seach for radio signals from intelligent life in the universe, while others look for places where the simplest forms of life may exist. An astrobiologist is usually an expert in biology as well as in astronomy.

ESCAPE VELOCITY

What does escape velocity mean?
Escape velocity is the speed at which an object (like a rocket) has to travel to completely overcome a planet or moon's gravity and make it into space.

SATELLITE

What is a satellite?
A satellite is a smaller object in space which orbits around a larger object in space. Satellites can be either artificial, like the communications and weather satellites that orbit the Earth, or they can be natural, like our moon.

METEROIDS

"Shooting stars" or meteors are bits of material falling through Earth's atmosphere; they are heated to incandescence by the friction of the air. The bright trails as they are coming through the Earth's atmosphere are termed meteors, and these chunks as they are hurtling through space are called meteoroids. Large pieces that do not vaporize completely and reach the surface of the Earth are termed meteorites.

Scientists estimate that 1,000 tons to more than 10,000 tons of meteoritic material falls on the Earth each day. However, most of this material is very tiny - in the form of micrometeoroids or dust-like grains a few micrometers in size. (These particles are so tiny that the air resistance is enough to slow them sufficiently that they do not burn up, but rather fall gently to Earth.)

Where do they come from? They probably come from within our own solar system, rather than interstellar space. Their composition provides clues to their origins. They may share a common origin with the asteroids. Some meteoritic material is similar to the Earth and Moon and some is quite different. Some evidence indicates an origin from comets.

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KUIPER BELT

The Kuiper (pronounced Ki-Per) Belt is often called our solar system's 'final frontier.' This disk-shaped region of icy debris is about 12 to 15 billion kilometers (7.5 billion to 9.3 billion miles) from our Sun. Its existence confirmed only a decade ago, the Kuiper Belt and its collection of icy objects - KBOs - are an emerging area of research in planetary science.

The most recent exciting discovery to come out of the Kuiper Belt is "Quaoar" (Kwa-whar), officially known as 2002 LM60, a frozen world orbiting our sun about a billion miles beyond the orbit of Pluto. The tiny world's diameter is 1,300 km (800 miles) - about half the size of Pluto. It is the largest of the more than 500 Kuiper Belt Objects discovered in the last decade. Quaoar/2002 LM60 orbits our Sun in a near circle, more so than any of the other planets or bodies in our solar system.

Quaoar is still an unofficial name. The two scientists who discovered 2002 LM60 have asked the International Astronomical Union to name the tiny world "Quaoar" in honor of a Native American creation god.

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STARS

The sun is the nearest star to the earth. The heavenly bodies which shine like the sun due to their own energies are called stars.

A star looks bright because it is intrinsically bright. A star looks bright because it is intrinsically bright. On a clear night about 5000 stars can be seen in the sky with naked e3ye are such stars called naked eye stars.

The bright stars in the sky have been named as Sirius (Vyadha), Canopos (Agasti), Spica ((chitra), Arcturus (Swati), Polaris (Dharuva), etc.


SUN

Our Sun has inspired mythology in almost all cultures, including ancient Egyptians, Aztecs, Native Americans, and Chinese. We now know that the Sun is a huge, bright sphere of mostly ionized gas, about 4.5 billion years old, and is the closest star to Earth at a distance of about 150 million km. The next closest star - Proxima Centauri - is nearly 268,000 times farther away. There are millions of similar stars in the Milky Way Galaxy (and billions of galaxies in the universe). Our Sun supports life on Earth. It powers photosynthesis in green plants and is ultimately the source of all food and fossil fuel. The connection and interaction between the Sun and the Earth drive the seasons, currents in the ocean, weather, and climate.

The Sun is some 333,400 times more massive than Earth and contains 99.86 percent of the mass of the entire solar system. It is held together by gravitational attraction, producing immense pressure and temperature at its core (more than a billion times that of the atmosphere on Earth, with a density about 160 times that of water).

At the core, the temperature is 16 million degrees kelvin (K), which is sufficient to sustain thermonuclear fusion reactions. The released energy prevents the collapse of the Sun and keeps it in gaseous form. The total energy radiated is 383 billion trillion kilowatts, which is equivalent to the energy generated by 100 billion tons of TNT exploding each second.

In addition to the energy-producing solar core, the interior has two distinct regions: a radiative zone and a convective zone. From the edge of the core outward, first through the radiative zone and then through the convective zone, the temperature decreases from 8 million to 7,000 K. It takes a few hundred thousand years for photons to escape from the dense core and reach the surface.

The Sun's "surface," known as the photosphere, is just the visible 500-km-thick layer from which most of the Sun's radiation and light finally escape, and it is the place where sunspots are found. Above the photosphere lies the chromosphere ("sphere of color") that may be seen briefly during total solar eclipses as a reddish rim, caused by hot hydrogen atoms, around the Sun. Temperature steadily increases with altitude up to 50,000 K, while density drops to 100,000 times less than in the photosphere. Above the chromosphere lies the corona ("crown"), extending outward from the Sun in the form of the "solar wind" to the edge of the solar system. The corona is extremely hot - millions of degrees kelvin. Since it is physically impossible to transfer thermal energy from the cooler surface of the Sun to the much hotter corona, the source of coronal heating has been a scientific mystery for more than 60 years. Scientists believe that energy transfer has to be in the form of waves or magnetic energy. Likely solutions have emerged from recent SOHO and TRACE satellite observations, which found evidence for the upward transfer of magnetic energy from the Sun's surface toward the corona above. Researchers in NASA's Sun-Earth Connection Space Science theme study these myserious phenomena.

Ulysses is the first spacecraft to study the unexplored region of space above our Sun's poles.

The spacecraft was launched aboard the Space Shuttle Discovery and sent towards Jupiter with powerful booster rockets. After studying Jupiter for 17 days, Ulysses used the giant planet's gravity to hurl it into an orbit out of the Ecliptic Plane, where planets orbit our Sun. No manmade vehicle has the power to break out of the ecliptic plane, but with the help of Jupiter's powerful gravity Ulysses settled into an orbit that allows it to fly over the Sun's polar regions.

Now well into an extended mission, Ulysses continues to send back valuable information on the inner working of our star, especially its magnetic field and how it influences our solar system.

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MOON

Earth's Moon:

The regular daily and monthly rhythms of Earth's only natural satellite, the Moon, have guided timekeepers for thousands of years. Its influence on Earth's cycles, notably tides, has also been charted by many cultures in many ages. More than 70 spacecraft have been sent to the Moon; 12 astronauts have walked upon its surface and brought back 382 kg (842 pounds) of lunar rock and soil to Earth.

The presence of the Moon stabilizes Earth's wobble. This has led to a much more stable climate over billions of years, which may have affected the course of the development and growth of life on Earth.

How did the Moon come to be? The leading theory is that a Mars-sized body once hit Earth and the resulting debris (from both Earth and the impacting body) accumulated to form the Moon. Scientists believe that the Moon was formed approximately 4.5 billion years ago (the age of the oldest collected lunar rocks). When the Moon formed, its outer layers melted under very high temperatures, forming the lunar crust, probably from a global "magma ocean."

How far away is the moon?
The moon is at an average distance of 238,855 miles (384,400 kilometers) away from Earth. That is about the width of 30 Earths. Because the moon does not orbit Earth in a perfect circle, but instead travels in a slightly elliptical orbit, its distance from Earth varies between 225,700 miles (363,300 kilometers) and 252,000 miles (405,500 kilometers).




How small is the moon compared to Earth?
The moon has a diameter of 2,159 miles (3,476 kilometers) and is about one-quarter the size of Earth. The moon weighs about 80 times less than Earth.




Why is the moon covered with craters?
All of the moons and planets in our solar system have been hit by a lot of meteorites. This was especially true in the past when there were many more meteoroids traveling in our solar system than there are today. On Earth, we only see a few of these craters because they have been eroded away by wind, rain and other forces. On the moon, where there is no atmosphere, there is no weather to erode away the craters. Even the footprints of the astronauts who landed on the moon over 30 years ago are still there.

What is the temperature on the moon?
The temperature on the moon varies from -387 Fahrenheit (-233 Celsius), at night, to 253 Fahrenheit (123 Celsius) during the day. Because the moon has no atmosphere to protect it from some of the sun's rays or to help trap heat at night, its temperature varies greatly between day and night.

How many astronauts have walked on the moon?
A total of 12 astronauts have walked on the moon. The first two astronauts landed on the moon in 1969 and the last astronauts landed on the moon in 1972. These astronauts were part of the six Apollo missions which sent astronauts to the moon's surface. Each mission landed two astronauts.




Which astronauts walked on the moon?
The tweleve astronauts who walked on the moon were:

Neil Armstrong - Apollo 11 - July, 1969
Edwin "Buzz" Aldrin - Apollo 11 - July, 1969
Charles "Pete" Conrad - Apollo 12 - November, 1969
Alan Bean - Apollo 12 - November, 1969
Alan Shepard - Apollo 14 - February, 1971
Edgar Mitchell - Apollo 14 - February, 1971
David Scott - Apollo 15 - July, 1971
James Irwin - Apollo 15 - July, 1971
John Young - Apollo 16 - April, 1972
Charles Duke - Apollo 16 - April, 1972
Eugene Cernan - Apollo 17 - December, 1972
Harrison Schmitt - Apollo 17 - December, 1972




How does the moon shine?

The moon does not make its own light.
The light we see from the moon is really sunlight that is being reflected from the moon's surface.





How much would I weigh on the moon?

Because the moon has one sixth the gravity of Earth, you would weigh six times less than what you weigh on Earth. This is why the astronauts were able to move easily in their heavy space suits. In the photo to the right, John Young, commander of the Apollo 16 lunar landing mission, jumps up from the lunar surface as he salutes.




What causes a ring around the moon?
Rings around the moon are caused when moonlight passes through thin clouds of ice crystals high in Earth's atmosphere. As moonlight passes through the ice crystals, it is bent in a way similar to light passing through a lens. The shape of the ice crystals causes the moonlight to be focused into a ring. This is similar to the way water droplets in the lower atmosphere can bend sunlight to create a rainbow.



What is a blue moon?
A blue moon is what people call the second of two full moons that appear during the same month. A second full moon can appear within the same month because full moons occur about every 29.5 days. So if a full moon occurs in the first day or two of a month, except for February, a second full moon can occur during one of the last days of that month as well.



When did astronauts get to drive lunar rovers on the moon?
Between 1969 and 1972 the astronauts who landed on the moon were able to use lunar rovers. By driving around in the lunar rovers, astronauts were able to travel much farther and explore more of the moon. Before the use of lunar rovers, the astronauts could only travel by foot. Lunar rovers were used during the last three Apollo missions to the moon (Apollos 15, 16 and 17).



How many pounds of moon rocks were brought back to Earth?
842 pounds (382 kilograms) of rocks were brought back from the moon by the Apollo astronauts



How long does it take to travel to the moon?
It takes about 3 days for a spacecraft to reach the moon. During that time a spacecraft travels about 240,000 miles (386,400 kilometers) which is the distance between Earth and the moon.



How long is a day on the moon?
A day on the moon is 27.32 Earth days or 655.72 hours long.

How fast does the moon travel around Earth?
The moon orbits Earth at a speed of 2,288 miles per hour (3,683 kilometers per hour). During this time it travels a distance of 1,423,000 miles (2,290,000 kilometers).
Why does the moon follow me when I move?
The moon appears to follow you because it is very far away and objects like trees and houses that you pass by are really close by comparison. As you walk or drive along, things close like trees and houses appear to move between the moon and you. Because the moon is so far away, it doesn't seem to move at all and appears to be following you.
Information source :NASA Kids section

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MARS



Why is Mars reddish?
The surface of Mars has an orange-reddish color because its soil has iron oxide or rust particles in it. The sky on Mars often appears pink or light orange because the dust in the soil is blown into Mars' thin atmosphere by winds on Mars.




What is the highest mountain on Mars?
The highest mountain on Mars is also the highest mountain and volcano in the entire solar system. It is called Olympus Mons and is 16 miles (24 kilometers) high which makes it about three times higher than Mt. Everest. In addition to being very tall, it is also very wide (340 miles or 550 kilometers) and covers an area larger than the entire chain of Hawaiian islands. Olympus Mons is a very flat mountain which slopes by only 2 to 5 degrees. It is a shield volcano built up by eruptions of lava.


When did we first land a spacecraft on Mars?
The Viking landers were the first spacecraft to land on Mars in the 1970s. Viking 1 and Viking 2 each had both an orbiter and a lander. On July 20, 1976 the Viking 1 Lander separated from the Orbiter and touched down on the surface of Mars. Less than two months later, on September 3, 1976, the Viking 2 lander touched down on Mars. These two landers took images of the Martian surface, studied soil samples, and studied the atmosphere of Mars.




How large is Mars compared to Earth?
Mars has a diameter of 4,222 miles (6,794 km) which makes it a little more than half (about 53%) the diameter of Earth. It has about one-ninth the mass of Earth.


How strong is the gravity on Mars?
Since Mars has less mass than Earth, the surface gravity on Mars is less than the surface gravity on Earth. The surface gravity on Mars is only about 38% of the surface gravity on Earth, so if you weigh 100 pounds on Earth, you would weigh only 38 pounds on Mars.
How long is a day on Mars?
A planet's day is the time it takes the planet to rotate or spin once on its axis. Mars rotates at almost the same speed as the Earth so a day on Mars is about as long as a day on Earth. A day on Mars is 24.62 hours long while a day on Earth is 23.934 hours long.
How long does it take Mars to go around the sun?
Mars revolves or orbits around the sun once every 1.88 Earth years, or once every 686.93 Earth days. Mars travels at an average speed of 53,979 miles per hour or 86,871 kilometers per hour in its orbit around the sun.


How bad are the dust storms on Mars?
Mars is famous for its large, planet-wide dust storms. Mars has an atmosphere which is much thinner than the atmosphere on Earth, but which still creates winds. When these winds pick up the fine, dry particles of dust on Mars a dust storm can occur. Most dust storms cover an area for a few days and carry small particles of dust at speeds of 33 to 66 miles per hour. Sometimes, though rarely, dust storms on Mars can be fierce enough to cover the entire planet in a dusty haze for weeks.



Does Mars have any moons?
Yes, Mars has two small moons named Phobos and Deimos. Their names mean fear and panic in Latin. Phobos and Deimos are not round like our moon. They are much smaller and have irregular shapes. Phobos is 13.8 miles (22.2 km) across and Deimos is only 7.8 miles (12.6 km) across. Both moons are covered with craters and are made of rock and iron. It is possible that Phobos and Deimos were two asteroids which were captured by the gravity of Mars.



Is there water on Mars?
Yes, there is water on Mars but it is frozen under the north and south polar ice caps. The polar ice caps, which were once thought to be made up of only dry ice (frozen carbon dioxide), are now known to have water ice beneath a top layer of dry ice. Mars has a lot of flood and river channels suggesting that a long time ago liquid water flowed on Mars during a time when Mars was a warm and wet planet with a thicker atmosphere. There is recent evidence that there may also be liquid water at or near the surface on Mars in some places, but this has yet to be proven.




Does Mars have an atmosphere?
Yes, Mars does have an atmosphere. The Martian atmosphere contains about 95.3% carbon dioxide (CO2) and 2.7% nitrogen, with the remainder a mixture of other gases. However, it is a very thin atmosphere, roughly 100 times less dense than Earth's atmosphere. Note: If Mars did not have an atmosphere images taken from the surface of Mars (like the one to the right) would show a black sky, even during the day.




Can we breath on Mars?
Mars does have an atmosphere, but it is about 100 times thinner than Earth's atmosphere and it has very little oxygen. The atmosphere on Mars is made up of mainly carbon dioxide. An astronaut on Mars would not be able to breath the martian air and would need a spacesuit with oxygen to work outdoors.



What is the temperature on Mars?
The temperature on Mars ranges between about -125 and 23 Fahrenheit (-87 to -5 Celsius).

Is there life on Mars?
This is a question which scientists and others have been asking for a long time because Mars is more similar to Earth than any other planet in the solar system. There is also evidence that liquid water flowed on Mars in the past and that there is frozen water under the poles of Mars. Spacecraft have been sent to Mars to either orbit or land on the planet since the 1960's. In 1976, NASA's two Viking landers touched down on the surface of Mars. Part of their mission was to collect soil with a robotic arm and study it to see if there were any signs of life, such as bacteria. Thousands of images were taken of the surface of Mars as well, but so far no evidence of life has been found. Future missions are being planned to continue the search for life on Mars. These missions will land at different locations and dig deeper in the soil to look for signs of life.

When did the first robot rover go to Mars?
The first robot rover to land and travel on Mars was the Mars Pathfinder's Sojourner Rover. It rolled onto Mars' surface on July 6, 1997. The Sojourner Rover was a six-wheeled vehicle that was controlled remotely by an operator here on Earth. Because of the distance to Mars, commands sent to the rover from Earth took about 10 minutes to reach it. Also, information sent back by the rover took another 10 minutes to reach Earth. The rover's mission was to gather information about the soil and rocks of Mars. Information on Sojourner Rover's performance on Mars has been used to help design even better robot rovers for future missions.


Is there really a giant canyon on Mars?
Yes, Mars has the largest canyon in the entire solar system. It is called Valles Marineris which means Valley of the Mariners (Mariner is another word for sailor or navigator). It is about 2,500 miles (4,000 km) long, 125 miles (200 km) wide, and about 4 miles (7 km) deep. Valles Marineris is about as long as the United States and it covers about 1/5 the distance around Mars. The canyon runs along the Martian equator and is thought to have formed from a giant crack that expanded as Mars cooled after its formation.



Who discovered Mars?
There is no single person who is credited with the discovery of Mars. Mars is one of the five planets that can be seen in the night sky without using a telescope or binoculars. Since Mars is bright and has a reddish color, it stands out and is easily noticed. The planet Mars has been known since ancient times and was observed for thousands of years by the people of many different cultures.



How long does it take to get to Mars from Earth?
The distance between Earth and Mars varies depending on where the two planets are in their orbits around the sun. So the time it takes to travel to Venus from Earth depends on the distance between the two planets at the time of launch. It also depends on the speed of the spacecraft and the path chosen. Below is a list of launch and arrival times between Earth and Mars for some past missions.
MISSION LAUNCHED MARS ARRIVAL
Spirit June 10, 2003 Jan 3, 2004
Pathfinder Dec 4, 1996 July 4, 1997
Viking 1 Aug 20, 1975 June 19, 1976
Viking 2 Sept 9, 1975 Aug 7, 1976
Mariner 9 May 30, 1971 Nov 14, 1971
How did Mars and its moons get their names?
The Romans knew of seven bright objects in the sky, the sun, the moon and the five brightest planets. They named them after their most important gods. The Romans were great soldiers and thought Mars, the god of war, was very important. Mars, the red planet, was named after this god of war. According to Roman myth, Mars rode on a chariot pulled by two horses named Phobos and Deimos (meaning fear and panic). The two small moons of Mars are named after these two mythical horses.


Was life discovered in a meterorite from Mars?
In 1984, a meteorite which was ejected from Mars about 16 million years ago was found by a group of scientists in Antarctica. It traveled for a long time in space before hitting Earth about 13 thousand years ago. The meteorite, called meteorite ALH84001, was carefully studied. Scientists discovered that the meteorite was about 4.5 billion years old and could have been on Mars when Mars had liquid water and possibly life. Studies showed that the Mars meteorite had grains of carbonate minerals which needed liquid water to form. Also, scientists discovered tiny tube-like structures within the meteorite which looked like fossilized microbial life (life that is so small that you can only see it through a microscope) and organic molecules. This may be evidence that Mars once had life. However, there are also some scientists who think that the tube-like structures cannot be ancient mircroscopic life because they are too small.


How old is Mars?
Mars was formed at the same time as the rest of the solar system, from a large spinning disk of gas and dust. Astronomers think that all this happened about 4.6 billion years ago! So Mars is about 4.6 billion years old.

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MERCURY



How hot is Mercury?
Since Mercury is the closest planet to the sun, spins slowly, and does not have much of an atmosphere to trap heat, its temperature varies greatly. Mercury's temperatures can go between -300 Fahrenheit (-183 Celsius) at night to 872 Fahrenheit (467 Celsius) during the day (This is hot enough)



Why does Mercury have more craters than the other planets?
All of the planets in our solar system have had a lot of craters. This was especially true in the past when there were many more meteoroids traveling in our solar system than there are today. On planets like Venus, Earth and Mars, we do not see as many craters because most of them have been eroded away by wind, rain, volcanic activity and other forces. On the giant gas planets, Jupiter, Saturn, Uranus and Neptune, we do not see any craters because there is no visible solid surface for the meteors to hit. The planet Pluto is probably also covered by craters, but we do not yet have good enough pictures to see them because Pluto is so far away. On the Mercury, where there is no atmosphere, there is no weather to erode away the craters, so most of the craters are still visible.


How small is Mercury compared to Earth?
Mercury is the second smallest planet in the solar system (only Pluto is smaller). Mercury has a diameter of 3,025 miles making it about one third the size of Earth. If Earth were the size of a baseball, Mercury would be about the size of a golf ball. Mercury is only a little larger than the moon.


How strong is the gravity on Mercury?
Since Mercury has less mass than Earth, the surface gravity on Mercury is less than the surface gravity on Earth. The surface gravity on Mercury is only about 38% of the surface gravity on Earth, so if you weigh 100 pounds on Earth, you would weigh only 38 pounds on Mercury.

How close is Mercury to the sun?
Mercury is the closest planet to the sun. It's orbit around the sun is very elliptical, like a stretched out circle. Mercury's distance from the sun ranges from 28.6 million miles (46 million km) to 43.4 million miles (69.8 million km).


Is there any water on Mercury?
Recent radar data shows that water ice may exist in the bottoms of craters at Mercury's poles. Although Mercury is the closest planet to the sun, and can be extremely hot over most of its surface, ice may exist at the bottoms of some polar craters because the crater floors are permanently shadowed by the crater rims. Mercury's axis has almost no tilt, so its poles receive very little direct sunlight.



How fast does Mercury orbit the sun?
Mercury circles the sun in only 88 days, compared to 365 days for Earth, at at a speed of nearly 31 miles (50 kilometers) per second. This is faster than any other planet in the solar system.
How did Mercury get its name?
The Romans knew of seven bright objects in the sky, the sun, the moon and the five brightest planets. They named them after their most important gods. Because Mercury was the fastest planet as it moved around the sun, it was named after the Roman messenger god Mercury. Mercury was also the god of travelers. According to myth, he had a winged hat and sandals, so he could fly.


How long does it take to get to Mercury from Earth?
How long it would take to travel to Mercury would depend on where Earth and Mercury were in their orbits at the time a spacecraft started its journey from Earth, and also on the path chosen. For example, Mariner 10 was launched on November 3, 1973 and it arrived at Mercury on March 29, 1974.





How many spacecraft have been to Mercury?
Only one spacecraft has ever visited the planet Mercury. It was called Mariner 10. During 1974 and 1975, Mariner 10 flew by Mercury three times and mapped about half of the planet's surface. Mariner 10 also discovered Mercury's thin atmosphere and detected its magnetic field.



What is the inside of Mercury made of ?
Mercury is a rocky planet with a huge iron core which makes up a large part of its interior. The core takes up more than 3/4 of the planet's diameter. Mercury's iron core is about the size of the moon. Iron makes up about 70% of Mercury's total weight making Mercury the most iron-rich planet in the solar system. On top of this core is a 430 mile (700 kilometer) thick layer of rocky crust.


What does the sun look like from Mercury?
Since Mercury is the closest planet to the sun, the sun would look much larger from Mercury than it would from any other planet in the solar system. From Mercury the sun would appear to be about 2 1/2 times larger than it appears from Earth.


How long is a day on Mercury?
A planet's day is the time it takes the planet to rotate or spin once on its axis. Mercury rotates very slowly compared to Earth so a day on Mercury is much shorter than a day on Earth. A day on Mercury is 58.646 Earth days or 1407.5 hours long while a day on Earth is 23.934 hours long.
How long is a year on Mercury?
A year on Mercury is about 88 Earth days long. Mercury has the shortest year of any planet in the solar system.
How far is Mercury from Earth?
Mercury is the first planet from sun and Earth is the third planet from the sun. Mercury is an average distance of 48 million miles (77 million km) from Earth.
Does Mercury have an atmosphere?
Mercury has an extremely thin atmosphere which is made up of atoms blasted off its surface by the solar wind, a constant stream of particles coming from the outer layer of the sun. Because Mercury is so hot, these atoms quickly escape into space. Unlike the stable atmospheres of Earth and Venus, Mercury's atmosphere is constantly being replenished.
What is the weather like on Mercury?
Since Mercury has hardly any atmosphere, it does not have weather like storms, clouds, winds or rain. Its surface temperature can reach 873 Fahrenheit (because it is so close to the Sun) and can drop to -297 Fahrenheit at night (because there is no atmosphere to trap the daytime heat).

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VENUS


Why is Venus sometimes called Earth's twin?
Venus is sometimes called Earth's twin because Venus and Earth are almost the same size, have about the same mass (they weigh about the same), and have a very similar composition (are made of the same material). They are also neighboring planets. However, Venus and Earth are also very different. Venus has an atmosphere that is about 100 times thicker than Earth's and has surface temperatures that are extremely hot. Venus does not have life or water oceans like Earth does. Venus also rotates backwards compared to Earth and the other planets.




Why is Venus so hot?
Venus is so hot because it is surrounded by a very thick atmosphere which is about 100 times more massive than our atmosphere here on Earth. As sunlight passes through the atmosphere it heats up the surface of Venus. Most of this heat cannot escape back into space because it is blocked by the very thick atmosphere of Venus. The heat becomes trapped and builds up to extremely high temperatures. This trapping of heat by the atmosphere is called the greenhouse effect because it is similar to how the glass in a greenhouse traps heat. The greenhouse effect on Venus causes the temperatures at its surface to reach 864 degrees Fahrenheit (462 degrees Celsius), making Venus the hottest planet in the entire solar system!





Could life exist on Venus?
Most astronomers feel that it would be impossible for life to exist on Venus. Today, Venus is a very hostile place. It is a very dry planet with no evidence of water, its surface temperature is hot enough to melt lead, and its atmosphere is so thick that the air pressure on its surface is over 90 times that on Earth. Even the spacecraft which have landed on Venus only survived for about an hour before being crushed and melted. There are however, a few scientists who think that it is possible for life to exist in the clouds of Venus.



Who discovered Venus?
There is no single person who is credited with the discovery of Venus. Venus is the brightest of the five planets that can be seen in the night sky without the use of a telescope or binoculars. Since Venus is so bright and noticable in the sky, it was probably seen by the first groups of humans.
How did Venus get its name?
The Romans knew of seven bright objects in the sky, the sun, the moon and the five brightest planets. They named them after their most important gods. Venus, the brightest planet in the night sky, was named after the Roman goddess of love and beauty.


Why is Venus so bright in the night sky?
Venus is one of the brightest objects in the night sky. Venus is so bright because its thick clouds reflect most of the sunlight that reaches it (about 70%) back into space, and because it is the closest planet to Earth. Venus can often be seen within a few hours after sunset or before sunrise as the brightest object in the sky (other than the moon). It looks like a very bright star. Venus is the brightest planet in the solar system.



What is the atmosphere of Venus like?
The atmosphere of Venus is very thick and is about 90 times more massive than Earth's atmosphere. It is mostly carbon dioxide gas (about 96%), with some nitrogen (about 3%) and a very small amount of water vapor (0.003%). Venus also has a thick layer of sulfuric acid clouds. The sulfur in the clouds gives Venus its yellowish appearance. The clouds in Venus's atmosphere also move very fast, reaching speeds of 220 miles per hour (350 km per hour).




Has a spacecraft ever landed on Venus?
Yes, several landers from the former Soviet Union have landed on Venus. They were only able to send us information for a short time because the extremely high temperature and pressure on the surface of Venus melted and crushed the landers. On December 15, 1970 an unmanned Soviet spacecraft, Venera 7, became the first spacecraft to land on another planet. It measured the temperature of the atmosphere on Venus. In 1972, Venera 8 gathered atmospheric and surface data for 50 minutes after landing. On Oct. 22, 1975, Venera 9 landed on the surface of Venus. It took the first close-up photograph of the planet's surface. Three days later Venera 10 landed on Venus. Venera 10 took photographs of its surface and studied its rocks. In December 1978, Venera 11 and Venera 12 landed on Venus and sent back more data on the atmosphere of Venus. Venera 12 sent back data for 110 minutes (the longest of any Venera lander) before the effects of heat and pressure ended its mission. In March 1982 two more Soviet spacecraft landed on Venus - Venera 13 and Venera 14. They sent back images and studied soil.

What is the surface of Venus like?
The surface of Venus is a very hot and dry place. Most of the surface is made up of gently rolling plains. Venus has several large lowlands and two large highland areas which are about the size of Australia and South America. Venus has several mountains and volcanoes and much of its surface is covered with old lava flows. The highest mountain on Venus is Maxwell Montes. It is more than 7 miles high and is higher than Mt Everest. Venus does not have many craters because most meteors burn up in its thick atmosphere and many of the meteor craters which did exist have been covered by lava flows. The images above are computer generated views of the surface of Venus using information from radar maps of the surface. The atmosphere of Venus is too thick for us to see its surface, however, radar can pass through the thick atmosphere of Venus, allowing us to find out what the surface is like.

How strong is the gravity on Venus?
Since Venus and Earth are almost the same size and have about the same mass, the surface gravity on Venus is almost the same as the surface gravity on Earth. The surface gravity on Venus is about 91% of the surface gravity on Earth, so if you weigh 100 pounds on Earth, you would weigh 91 pounds on Venus.
How old is Venus?
Venus was formed at the same time as the rest of the solar system, from a large spinning disk of gas and dust. Astronomers think that all this happened about 4.6 billion years ago! So Venus is about 4.6 billion years old.
Does Venus really spin backwards?
Yes, Venus spins backwards compared to most of the other planets. It spins or rotates in the opposite direction that Earth rotates. This means that on Venus the sun rises in the west and sets in the east. On Earth the sun rises in the east and sets in the west. Venus also spins very slowly - only once every 243 Earth days. Venus is the slowest spinning planet in the solar system. Actually, a day on Venus is longer than a year on Venus! A year on Venus (the time it takes for it to orbit the sun) is 225 Earth days.
How far is Venus from the sun?
The average distance of Venus from the sun is 67,237,910 miles or 108,208,930 km. Since Venus travels in an elliptical orbit around the sun, its distance from the sun varies throughout its year from 66,782,000 miles (107,476,000 km) to 67,693,000 miles (108,942,000 km).
How far away is Venus from Earth?
The planet Venus is the second planet from the sun and Earth is the third. Venus is the closest planet to Earth. It is about 25 million miles (40 million kilometers) away from Earth.

How long does it take to get to Venus from Earth?
The distance between Earth and Venus varies depending on where the two planets are in their orbits around the sun. So the time it takes to travel to Venus from Earth depends on the distance between the two planets at the time of launch. It also depends on the speed of the spacecraft and the path chosen. Below is a list of launch and arrival times between Earth and Venus for some past missions.
MISSION   LAUNCHED   VENUS ARRIVAL  
Mariner 2 Aug 27, 1962 Dec 14, 1962
Mariner 5 June 14, 1967 Oct 19, 1967
Mariner 10 Nov 3, 1973 Feb 5, 1974
Pioneer May 20, 1978 Dec 4, 1978
Magellan May 4, 1989 Aug 10, 1990


How long is a day on Venus?
A planet's day is the time it takes the planet to rotate or spin once on its axis. Venus rotates much more slowly than Earth does, so a day on Venus is much longer than a day on Earth. A day on Venus lasts for 243 Earth days or 5,832 hours! A day on Earth is 23.943 hours. Venus also rotates backwards compared to the Earth and most of the other planets.
How long does it take Venus to go around the sun?
Venus revolves or orbits around the sun once every 0.615 Earth years, or once every 224.7 Earth days. Venus travels at an average speed of 78,341 miles per hour or 126,077 kilometers per hour in its orbit around the sun.

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SATURN


How big is Saturn?
Saturn is the second largest planet in our solar system. Only Jupiter is larger. Saturn is 72 thousand miles (120,000 km) in diameter and is almost ten times the diameter of Earth. About 755 Earths could fit inside Saturn. If you had a ball that was the size of a dime, Saturn would be a little bigger than a soccer ball.



How did Saturn get its rings?
Saturn's rings probably formed when objects like comets, asteroids or even moons broke up in orbit around Saturn due to Saturn's very strong gravity. The pieces of these objects kept colliding with each other and broke into even smaller pieces. These pieces gradually spread around Saturn to form its rings.



How large are Saturn's rings?
Saturn's rings are about 168,000 miles (250,000 km) across, but only about 5 miles (9 km) thick. If you had a model of Saturn that was a meter stick wide (3 feet), its rings would be 10,000 times thinner than a razor blade! Saturn and its rings would just fit in the distance between Earth and the moon. If all of the pieces of the rings were put together, they would make a ball that would be between 55 to 115 feet (100 to 200 km) wide.




What are Saturn's rings made of?
Saturn's rings are made of billions of pieces of ice, dust and rocks. Some of these particles are as small as a grain of salt, while others are as big as houses. These chucks of rock and ice are thought to be pieces of comets, asteroids or even moons which were torn apart by the strong gravity of Saturn before they could reach the planet.




How many rings does Saturn have?
Saturn has four main groups of rings and three fainter, narrower ring groups. These groups are separated by gaps called divisions. Close up views of Saturn's rings by the Voyager spacecrafts, which flew by them in 1980 and 1981, showed that these seven ring groups are made up of thousands of smaller rings. The exact number is not known.


What holds Saturn's rings together?
Saturn's rings are held together by gravity. Saturn also has several shepherd moons, small moons that orbit near the outer edges of rings or within gaps in the rings. The gravity of shepherd moons serves to maintain a sharply defined edge to the ring.
How strong is the gravity on Saturn?
Although Saturn is much larger than Earth, its surface gravity is less than the surface gravity on Earth. This is because Saturn is made up of gases and is not solid like Earth. This makes Saturn very light for its size. Actually, Saturn has the lowest density of all the planets in our solar system! The surface gravity on Saturn is about 74% of the surface gravity on Earth, so if you weigh 100 pounds on Earth, you would weigh 74 pounds on Saturn.


Can Saturn really float on water?
Yes, if you could find a big enough body of water for it to float on. Saturn is very large and is the second largest planet in the solar system. However, it is made up mostly of gas and is less dense than water. Since it is lighter than water, it can float on water. None of the other planets in our solar system can do this because they have a higher density and are heavier than water. Saturn has the lowest density of all the planets, which means that it does not weigh as much for its size as the other planets do.


How did Saturn get its name?
The Romans knew of seven bright objects in the sky, the sun, the moon and five brightest planets. They named them after their most important gods. Saturn was named after the Roman god of agriculture. According to myth, Saturn introduced agriculture to his people by teaching them how to farm the land. Saturn was also the Roman god of time and this is perhaps why the slowest (in orbit around the sun) of the five bright planets was named after him. In Roman mythology Saturn was the father of Jupiter. Saturday is also named after the Roman god Saturn (Saturn's Day).
What is Saturn made of?
Saturn is not solid like Earth, but is instead a giant gas planet. It is made up of 94% hydrogen, 6% helium and small amounts of methane and ammonia. Hydrogen and helium are what most stars are made of. It is thought that there might be a molten, rocky core about the size of Earth deep within Saturn.
If I stood on Saturn would I sink?
The outer part of Saturn is made of gas and the very top layers have about the same pressure as the air does on Earth. So, if you tried to walk on this part of Saturn, you would sink through its atmosphere. Saturn's atmosphere is very thick and its pressure increases the deeper you go. After a while, you would stop sinking and unfortunately be crushed by the high pressure deeper in Saturn's atmosphere.
How many moons does Saturn have?
Saturn has 31 known moons. The largest ones are shown above. Saturn's largest moon Titan is bigger than both Mercury and Pluto. Titan has a very thick atmosphere which is mostly nitrogen. Earth's atmosphere is also mostly nitrogen. Saturn also has many icy moons like Mimas which has a large crater that is 1/4 the diameter of the moon, and Enceladus which has very dark material covering one side and very bright material on the other side. Some of Saturn's smaller moons help keep Saturn's rings stable by orbiting in or near the rings. These moons are called "shepherd moons" and use their gravity to keep the small ring particles in a stable orbit. Some of the gaps in Saturn's rings are caused by these moons.
Where is Saturn?
Saturn is the 6th planet from the sun in our solar system. It is about 870 million miles (1.4 billion km) from the sun and about 780 million miles (1.3 billion km) from Earth. Saturn is about 9.6 times farther from the sun than Earth is. Saturn is almost twice as far from the sun as Jupiter, the 5th planet, is.
How long is a day on Saturn?
A planet's day is the time it takes the planet to rotate or spin once on its axis. Saturn rotates faster than Earth so a day on Saturn is shorter than a day on Earth. A day on Saturn is 10.656 hours long while a day on Earth is 23.934 hours long.


How many spacecraft have been to Saturn?
Three spacecraft have flown by Saturn so far, and a forth is scheduled to visit Saturn in 2004. In 1979, Pioneer 11 became the first spacecraft to fly by and study Saturn up close. Voyager 1 flew by in 1980 and Voyager 2 in 1981. These spacecraft studied many of the moons of Saturn as well. The Pioneer and Voyager missions made many important discoveries and sent back wonderful close-up images of Saturn and its moons. In July 2004, the Cassini spacecraft, which was launched in October 1997, will reach Saturn and send back even more information and images.


How long does it take to get to Saturn from Earth?
The distance between Earth and Saturn varies depending on where the two planets are in their orbits around the sun. So the time it takes to travel to Saturn from Earth depends on the distance between the two planets at the time of launch. It also depends on the speed of the spacecraft and the path chosen. Below is a list of launch and arrival times between Earth and Saturn for some past missions.
MISSION   LAUNCHED   SATURN ARRIVAL  
Voyager 1 Sept 5, 1977 Nov 12, 1980
Voyager 1 Aug 20, 1977 Aug 26, 1981
Pioneer 11 April 5, 1973 Sept 1, 1979

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NEPTUNE


Why is Neptune blue?
Neptune's atmosphere is made up of hydrogen, helium and methane. The methane in Neptune's upper atmosphere absorbs the red light from the sun but reflects the blue light from the sun back into space. This is why Neptune appear blue.


How did Neptune get its name?
The Romans named the five planets closest to the sun after their most important gods. These were the only planets that were bright enough for them to see. Later, when telscopes were used, other planets were discovered. Astronomers decided to continue naming the Planets after Roman Gods. Neptune, a blueish planet, was named after the Roman god of the Sea.



How many moons does Neptune have?
Neptune has thirteen moons that we know of. The largest moon is Triton (shown to the left). Triton is slightly smaller than Earth's moon and has active volcanoes which erupt like geysers and eject nitrogen frost over the surface. The other moons of Neptune are Nereid, Proteus, Larissa, Despina, Galatea, Thalassa, and Naiad. These moons are much smaller than Triton and except for Nereid, were not discovered until the Voyager spacecraft flew by them in 1989.




How big is Neptune?
Neptune is the fourth largest planet in our solar system and it is the smallest of the giant gas planets. Neptune has a diameter of 34,503 miles (55,528) kilometers. Its volume is 57.7 times the volume of Earth which means that 57 Earths could fit inside of Neptune with a little room left over.


How strong is the gravity on Neptune?
Although Neptune is much larger than Earth, its surface gravity is about the same as the surface gravity on Earth. This is because Neptune is made up of gases and is not solid like Earth. This makes Neptune very light for its size. The surface gravity on Neptune is about 110% of the surface gravity on Earth, so if you weigh 100 pounds on Earth, you would weigh 110 pounds on Neptune.


How long does it take to get to Neptune from Earth?
How long it would take to get to Neptune from Earth would depend on the path chosen and on where Neptune and Earth were in their orbits when the mission was launched. For example, the Voyager 2 spacecraft was launched on Aug 20, 1977 and it reached Neptune on Aug 24, 1989. So, Voyager 2 took about twelve years to reach Neptune.


How far away is Neptune from the sun?
The average distance of Neptune from the sun is 2,795,084,800 miles or 4,498,252,900 kilometers. Because its orbit is elliptical, its distance from the sun changes depending on where it is in its orbit. The closest Neptune gets to the sun is 2,771,087,000 miles or 4,459,630,000 kilometers. The farthest it gets from the sun is 2,819,080,000 miles or 4,536,870,000 kilometers.
How long is a day on Neptune?
A planet's day is the time it takes the planet to rotate or spin once on its axis. Neptune rotates faster than Earth so a day on Neptune is shorter than a day on Earth. A day on Neptune is about 16 Earth hours while a day on Earth is about 24 hours.
When was Neptune discovered?
Neptune was the first planet to be discovered by using mathematics. After the discovery of Uranus in 1781, astronomers noticed that the planet was being pulled slightly out of its normal orbit. John Couch Adams of Britain and Urbain Jean Joseph Leverrier of France, used mathematics to predict that the gravity from another planet beyond Uranus was affecting the orbit of Uranus. They figured out not only where the planet was, but also how much mass it had. A young astronomer, Johann Gottfried Galle, decided to search for the predicted planet and observed Neptune for the first time in 1846.


Does Neptune have rings?
Yes, Neptune has several faint rings around it. There are three main rings which are very thin and dark. The rings are made up of small rocks and dust. Neptune's rings are not the same thickness all around. There are areas of the rings which are much thicker than other areas of the rings. These thicker parts are called ring arcs. Some of these ring arcs are also twisted. Because Neputune's rings are so dark and faint, they were not discovered until the 1980s.



What is the Great Dark Spot?
The Great Dark Spot was a hugh spinning storm in the southern atmosphere of Neptune which was about the size of the entie Earth. Winds in this storm were measured at speeds of up to 1,500 miles per hour. These were the strongest winds ever recorded on any planet in the solar system! The Great Dark Spot was first discovered when the Voyager 2 spacecraft flew by Neptune in 1989. When the Hubble Space Telescope looked at Neptune in 1994, the Great Dark Spot was gone and a different dark spot was in the northern atmosphere of Neptune.




What is the weather like on Neptune?
Neptune has the wildest and strangest weather in the entire solar system. It has huge storms with extremely high winds. Its atmosphere has dark spots which come and go, and bright cirrus-like clouds which change rapidly. Neptune has an average temperature of about -350 Fahrenheit (-212 Celsius). On Earth sunlight drives our weather, but Neptune is so far away that it receives a thousand times less sunlight than Earth does. How Neptune gets the energy for such intense weather is still a mystery.




Is Neptune sometimes the farthest planet?
Because Pluto has an orbit around the sun which is very elliptical, there are times when it crosses Neptune's orbit and becomes the 8th planet from the sun instead of the 9th. When this happens, Neptune becomes the 9th and farthest planet in the solar system. For 20 years, from 1979 to 1999, Neptune was actually farther from the sun than Pluto. For now, Pluto is back to being the 9th and farthest planet from the sun. It will be more than 230 years before Neptune and Pluto trade places again. Pluto slips inside of Neptune's orbit once every 248 Earth years for a period of twenty years.


JUPITER


How long is a day on Jupiter?
Jupiter is the fastest spinning planet in our solar system rotating on average once in just under 10 hours. That is very fast especially considering how large Jupiter is. This means that Jupiter has the shortest day of all the planets in the solar system. Since Jupiter is a gas planet, it does not rotate as a solid sphere. Jupiter's equator rotates a bit faster than its polar regions at a speed of 28,273 miles/hour (about 43,000 kilometers/hour). Jupiter's day varies from 9 hours and 56 minutes around the poles to 9 hours and 50 minutes close to the equator.


How long does it take Jupiter to go around the sun?
Jupiter revolves or orbits around the sun once every 11.86 Earth years, or once every 4,330.6 Earth days. Jupiter travels at an average speed of 29,236 miles per hour or 47,051 kilometers per hour in its orbit around the sun.

What is the Great Red Spot on Jupiter?
The Great Red Spot is a giant, spinning storm in Jupiter's atmosphere. It is like a hurricane on Earth, but it is much larger. Jupiter's Great Red Spot is more than twice the size of Earth! Winds inside this storm reach speeds of about 270 miles per hour. Nobody knows when the Great Red Spot first appeared on Jupiter, but it has been seen on Jupiter ever since people started looking through telescopes about 400 years ago.




How large is Juptier compared to Earth?
Jupiter has a diameter of about 88,695 miles (142,800 kilometers) which is more than 11 times the diameter of Earth. It's volume is over 1,300 times the volume of Earth. This means that Jupiter is so big that over 1,300 Earths could fit inside of it. Jupiter is so big that it weighs two and a half times the weight of all of the other eight planets put together!


How strong is the gravity on Jupiter?
The gravity on Jupiter is greater than the gravity on Earth because Jupiter is more massive. Although Jupiter is a great deal larger in size, its surface gravity is just 2.4 times that of the surface gravity of Earth. This is because Jupiter is primarily made up of gases. If you weigh 100 pounds on Earth, you would weigh 214 pounds on Jupiter.

Does Jupiter have rings?
Yes, Jupiter does have faint, narrow rings. Unlike Saturn, which has bright ice rings, Jupiter has dark rings which are made up of dust and tiny pieces of rock. Jupiter's rings were discovered by NASA's Voyager 1 mission in 1980.


What are the stripes of color on Jupiter?
The stripes of color on Jupiter are its bands. There are two types of bands on Jupiter. The light colored bands are called zones. These are regions where gas in Jupiter's atmosphere is rising upwards. The dark bands are called belts. These are regions where the gas in Jupiter's atmosphere is sinking downwards. The colors in the bands are caused by slight differences in their temperatures and their composition (what chemicals are in them). Bands which are next to each other, have winds which move in opposite directions. In this false-colored image, the blue colored bands are the ones lowest in altitude, followed by the brown and white colored bands. The red colored bands are at the highest altitudes.



How long does it take to get to Jupiter from Earth?
The distance between Earth and Jupiter varies depending on where the two planets are in their orbits around the sun. So the time it takes to travel to Jupiter from Earth depends on the distance between the two planets at the time of launch. It also depends on the speed of the spacecraft and the path chosen. Below is a list of launch and arrival times between Earth and Jupiter for some past missions.
MISSION   LAUNCHED   JUPITER ARRIVAL  
Cassini Oct 15, 1997 July 1, 2004
Voyager 1 Sept 5, 1977 March 5, 1979
Voyager 2 Aug 20, 1977 July 9, 1979
Ulysses Oct 6, 1990 Dec 8, 1992
Pioneer 11 April 5, 1973 Dec 2, 1974

How did Jupiter get its name?
The Romans knew of seven bright objects in the sky, the sun, the moon and the five brightest planets. They named them after their most important gods. Jupiter, the largest planet, was named after the king of the Roman gods.

Did a comet really crash into Jupiter?
Yes, between July 16 and July 22, 1994, several pieces of Comet Shoemaker-Levy 9 collided with Jupiter. It was the first collision of two solar system objects ever observed. The comet had been captured and broken apart by Jupiter's strong gravity. More than 20 fragments of the comet crashed into Jupiter's southern hemisphere at speeds of about 130,000 miles (210,000 km) per hour. The impacts released a lot of energy and created several large, dark scars in Jupiter's atmosphere which lasted for several weeks.




How many moons does Jupiter have?
Jupiter has at least 61 known moons. The largest four are called Io, Europa, Ganymede and Callisto. These four moons are called the Galilean satellites because they were first seen in 1610 by the astronomer Galileo Galilei. Ganymede is the largest moon in the solar system, with a diameter of 3,260 miles. Io has a lot of active volcanoes and is covered with sulfer. Callisto may have a water ocean beneath its heavily cratered icy, rocky surface. Europa, which is covered by a cracked, icy surface, may also have a liquid water ocean. The other moons are smaller and have irregular shapes. Most of these small moons are thought to be asteroids which were caught by Jupiter's strong gravity.




Why does Io have so many volcanoes?
Io has hundreds of volcanoes, many of which are active. It is one of the most volcanically active bodies in the solar system. Io is heated up by the strong gravitional pulls of Jupiter on one one side and the large moons Europa, Ganymede and Callisto on the other. This gravitational tugging stretches and bends Io causing it to heat up. Io's surface is covered by large sulfur lava flows and irregularly shaped mountains. It is about the size of our moon.




What is the largest moon in the solar system?
One of Jupiter's moons, Ganymede, is the largest moon in the solar system. Ganymede has a diameter of 3270 miles (5,268 km) and is larger than the planets Mercury and Pluto. It has a rocky core with a water/ice mantle and a crust of rock and ice. Ganymede has mountains, valleys, craters and old lava flows.



Does Jupiter have a solid surface?
We do not yet know if a solid surface exists on Jupiter. Jupiter's clouds are thought to be about 30 miles (50 km) thick. Below this there is a 13,000 mile (21,000 km) thick layer of hydrogen and helium which changes from gas to liquid as the depth and pressure increase. Beneath the liquid hydrogen layer is a 25,000 mile (40,000 km) deep sea of liquid metallic hydrogen. Beneath this, there might be a solid core which is about one and a half times the size of Earth, but thirty times more massive. The temperature here would be about 55,000 Fahrenheit (30,000 Celsius) and the pressure would be tremendous because of the weight of the atmosphere above.
How old is Jupiter?
Jupiter was formed at the same time as the rest of the solar system, from a large spinning disk of gas and dust. Astronomers think that all this happened about 4.6 billion years ago! So Jupiter is about 4.6 billion years old.

Could there be life on Jupiter's moon Europa?
Europa is the fourth largest moon of Jupiter. Scientists think that life may exist on Europa because there is evidence that liquid water may exist beneath its icy surface. Europa is pushed and pulled by the high gravity of Jupiter as well as by the gravity of Jupiter's other moons. This makes Europa expand and contract and causes it to heat up and this heat may cause some of Euorpa's icy crust to melt under the surface. So, there may be lakes and oceans of liquid water on Europa. Water is a major requirement for life. If there is liquid water on Europa, there may be life.





NEBULA

What is a nebula?
A nebula is a cloud of gas and dust in space. Some nebulas are regions where new stars are being formed, while others are the remains of dead or dying stars. Nebulas come in many different shapes and sizes. There are four main types of nebulas: Planetary nebulas, Reflection nebulas, Emission nebulas, and Absorption nebulas. The word nebula comes from the Latin word for cloud.


What is a planetary nebula?
A planetary nebula is created when a star blows off its outer layers after it has run out of fuel to burn. These outer layers of gas expand into space, forming a nebula which is often the shape of a ring or bubble. About 200 years ago, William Herschel called these spherical clouds planetary nebulae because they were round like the planets. At the center of a planetary nebula the glowing, left-over central part of the star from which it came can usually still be seen.




What is a reflection nebula?
A reflection nebula is a cloud of gas and dust which does not create its own light, but instead shines by reflecting the light from nearby stars. The brightest reflection nebulas are places where new stars are being formed. Here the gas and dust is thick and shines by the light of new, bright stars. Sometimes the gas is so thick that the new stars cannot be seen.




What are the glowing clouds in space?
The glowing clouds that you see in pictures from space are called emission nebulas. A emission nebula is a cloud of hot, glowing cloud of gas and dust in space. These nebulas absorb the light of nearby stars and reach very high temperatures. The high temperature causes them to glow. Emission nebulas are often found in regions of space where new stars are forming.




What are the dark clouds in space?
The dark clouds in space are called absorption nebulas or dark nebulas. An absorption nebula is a cloud of gas and dust which blocks light from the regions of space behind it. As light from space reaches an absorption nebula it is absorbed by it and does not pass through. Absorption nebulas do not create their own light. It is hard to find an absorption nebula unless it is silhouetted against much brighter region of space.



BEYOND THE SOLAR SYSTEM

In 1991, the nine worlds of our own solar system were the only known planets. Astronomers did not believe that our Sun's environment was the only planet producer in the universe. But they had no evidence of planets outside our solar system.
How quickly things change.
In 1991 radio astronomers detected the first extrasolar planets orbiting a dying pulsar star. Although the deadly radiation from the pulsar is not condusive to life, it was the first example of a star other than our Sun producing planets.
Since then more than 100 planets have been found orbiting other stars. Some of them are orbiting extremely close to their parent star like the 51 Pegasi planetary.

Information source :NASA Kids section

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