Saturn’s moons

At least 46 moons orbit Saturn. Each moon is unique. Enceladus is among the shiniest objects in space. Titan’s atmosphere is thicker than Earth’s. Here are the big moons, seen from behind the moon Dione.

The solar system

The relative sizes of the eight planets and the three dwarf planets are shown in this diagram of the solar system. Jupiter is the largest planet. The Sun, of course, is much larger than any of the planets.

Jupiter’s moons

Jupiter, the largest planet in the solar system, has so many moons that we are constantly discovering new ones. This image shows some of the bigger moons and the gossamer rings around the planet.

What are the distinguishing features of each of the rocky planets?

Mercury is the closest to the Sun and therefore its temperature can be as high as 467 °C (873 °F). Venus is covered with carbon dioxide containing droplets of sulphuric acid. This traps the Sun’s heat and makes Venus hotter than even Mercury. Mars, the red planet, is considered to be the only planet after Earth where life could exist. As far as we know, the Earth is the only planet that supports life.

What makes gas giants unique?

The gas giants are bigger in size but lighter, as they are mainly made up of gases and ice particles. In fact, Saturn is so light that it would float if placed in water! Gas giants also spin extremely quickly and they have rings around them. These planets do not have a hard surface. Jupiter and Saturn have a semi-liquid centre that is covered by a layer of liquid gas.

What are the features of a rocky planet?

The rocky planets are made up of rocks and metals like iron and nickel. They are smaller than the gas giants but are very heavy. It is because of their weight that rocky planets rotate much slower than the gas giants.

How were the planets formed?

After the gaseous cloud called the solar nebula collapsed upon itself due to the strength of its own gravity and formed the Sun, the dust and particles around it clumped together to form the planets. The heat of the Sun melted the ice particles nearby and eventually these rocks grew larger to form the four rocky planets. Some ice particles were too far away from the Sun to be melted. These ice pieces combined with gases to form the planets called the gas giants.

How were the planets formed?

After the gaseous cloud called the solar nebula collapsed upon itself due to the strength of its own gravity and formed the Sun, the dust and particles around it clumped together to form the planets. The heat of the Sun melted the ice particlesnearby and eventually these rocks grew larger to form the four rocky planets. Some ice particles were too far away from the Sun to be melted. These ice pieces combined with gases to form the planets called the gas giants.

What are the Planets?

Planets are large masses of matter that orbit around a star. Our solar system consists of eight planets – Mercury, Venus, Earth, Mars, which are called inner or rocky planets, and Jupiter, Saturn, Uranus and Neptune, which are the outer planets, or gas giants.

What are the Planets?

Planets are large masses of matter that orbit around a star. Our solar system consists of eight planets – Mercury, Venus, Earth, Mars, which are called inner or rocky planets, and Jupiter, Saturn, Uranus and Neptune, which are the outer planets, or gas giants.

How did we learn about the Sun?

We have sent several solar missions into space to study the Sun and its characteristics. The first detailed observations were made by NASA’s Pioneer missions that were launched between 1959 and 1968. The Solar Maximum mission of 1980 made a detailed study of solar flares. The Solar and Heliospheric Observatory (SOHO) launched in 1995, has been continuously collecting data regarding the Sun for the last ten years.

The Sun takes about 26 days on average to rotate on its axis. Since it is made up of gas, different parts of the Sun rotateat different speeds. The surface closest to the equator rotates faster than that closest to the polar regions. The Sun’ssurface near the poles takes almost 36 days to complete one rotation.

Is the Sun really a star?

The Sun is a medium-sized star known as a yellow dwarf. It is younger and smaller than most stars in the universe, but is very bright and extremely hot. In about five billion years, when all the hydrogen in its core has been used up, the Sun will change into a red giant star. After that, the Sun will evolve into a white dwarf before finally dying out.

What is a solar flare?

Sometimes the Sun produces a huge amount of magnetic energy that sends out jets of gas into space. These jets of gas arecalled solar flares and cause a sudden increase in the brightness of the Sun. Solar flares are often followed by the release of electrically charged particles like protons and electrons. These are called solar winds and are known to travel at a speed of about 500 kilometres (300 miles) per second.

What is a solar eclipse?

A solar eclipse occurs when the Moon comes between the Sun and the Earth, blocking the Sun from our view. In a total solar eclipse, the Moon blocks out the Sun from our view completely. In a partial eclipse, however, a part of the Sun is visible. During an annular eclipse, we can see a small ring of the Sun glowing around the Moon. When the Moon is nearer to the Earth it appears larger and therefore covers the Sun completely, although it is actually much smaller than the Sun. However, in an annular eclipse the Moon is too far away from the Earth to block the Sun out totally and therefore a ring of sunlight is seen.

How was the Sun created?

Before it was formed, the Sun and the rest of the solar system was a huge mass of hot gas and dust called a solar nebula. This nebula spun faster and faster until the clouds of gases, dust and ice particles clumped together and exploded, forming the sun.

What is Sun?

Our solar system is made up of the Sun, eight planets, three dwarf planets and many asteroids, comets and other space rocksThe Sun is the largest object in the solar system and is located right at its centre. The planets, dwarf planets, asteroids and comets travel around the Sun in an ellipse. Our solar system was formed about 5 billion years ago, and the surface of the Sun is about 4.6 billion years old.

What are Heavenly pictures?

By drawing imaginary lines between the stars in the sky, you will notice the shapes of animals or objects familiar to you. You might see a crab, a dragon, a bear or other patterns. These star patterns are called constellations. Astronomers haveidentified 88 constellations in all. The more famous ones are the Great Bear, the Little Bear and Orion, also known as theHunter. The constellations also include characters from Greek mythology and the 12 signs of the zodiac.

What is a black hole?

Black holes are extremely compact space objects that were once massive stars. Sometimes a huge star begins to shrink until it is smaller than an atom. This is called a black hole. The centre of the black hole is called ‘singularity’.

The gravity near this point is so strong that any object that gets too close to the black hole is pulled into it. Even light gets sucked into it, which is why we can’t see a black hole. Scientists use special instruments to detect a black hole’spresence. They examine the effects it has on the objects near it.

Nobody can actually see a black hole, because the extremely strong gravity inside them does not even allow any light to escape, let alone anything else.This is an artist’s impression of what a black hole may be like.

What is a white dwarf?

A small star usually shrinks to form a dense white dwarf. The size of a white dwarf is similar to the size of Earth. There are many white dwarfs in our galaxy but they are too dim to be seen. Sirius B is one of them.

How long does a star live?

A star glows for millions of years until the gases in its outer layer begin to cool, and the hydrogen in the inner core is slowly used up. The cool outer layer starts to glow red. When this happens the star is called a red giant. The red giant continues to lose its brightness until it fades away. Depending on its size, a red giant may die in an explosion, get compressed to form a black hole or become a white dwarf.

What is a protostar?

Stars are born in clouds of dust and gases, mainly hydrogen. More and more gas is pulled together by gravity to form a cloud. After a while the cloud begins to spin. This makes the gas atoms bump into each other at high speeds, creating a great deal of heat. As the cloud becomes hotter a nuclear reaction takes place inside, and the cloud begins to glow. This glowing cloud is called a protostar. The protostar continues to contract until it becomes a star.

What is a Star?

A star is a huge ball of gas and dust that gives out both heat and light. When the gases in the star burn out, it dies. A star can live for millions, even billions, of years depending on its size. Each galaxy in the universe is made up of several billion stars.

A galactic crash

Sometimes, galaxies crash into one another due to the force of gravity. But the stars in them are too far apart to cause any real damage. Our own galaxy is on a collision course with its neighbour Andromeda. The collision will take place in about five billion years and the two will merge to form an elliptical (oval) galaxy.

Is the Milky Way a part of a cluster of galaxies?

The Milky Way and three of its neighbouring galaxies are part of a larger cluster known as the Local Group (because they are closest to Earth). The neighbouring galaxies in the Local Group are calledAndromeda, and the Large and Small Magellanic Clouds. Of the 35 galaxies in the Local Group, only these three can be seen with the naked eye.

How did the Milky Way get its name?

In ancient Greek and Roman myths, it was believed that the goddess Hera (Juno) spilt milk across the sky and called the white streak it left a ‘river of milk’. The Romans called it Via Lactea or a ‘road made of milk’. This is how our galaxy came to be named the Milky Way.

What is Messier Object 31?

The Andromeda Galaxy is also known as Messier Object 31 or M31. This galaxy is more than twice thesize of Milky Way. But it is still not the large galaxy we know of.

How big is the Milky Way?

The Milky Way is huge. It takes the Sun about 250 million years to orbit once around the centre of theMilky Way.

Which is the largest galaxy?

Scientists do not know exactly. The largest galaxies we know of a giant elliptical (oval) galaxies located in the middle of a whole group of galaxies. One of the largest is in the central galaxy in the cluster Abell 2029.

What is the Big Bang theory?

The Big Bang theory suggests that the universe as we know it today was created after a huge explosionor ‘bang’. Georges Lemaitre proposed the theory of the Big Bang in 1927, and in 1929 Edwin Hubbleexpanded on his work.

What is Galaxy?

A galaxy is a group of billions of stars, dust and gas bound together by gravitational force. A galaxy can either be on its own or in a cluster. Galaxies come in different shapes and sizes. Scientists have divided them into three categories based on their shapes – spiral, elliptical (oval) and irregular (no shape).

The universe is a huge open space made up of billions of galaxies and an even larger number of stars. Our galaxy is called the Milky Way. Our solar system, including the Sun, the planets and their moons, forms just a tiny part of the Milky Way.