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Online Education for Class 8 Science Chapter 17 Extra Questions and Answers Stars and the Solar System
What is the brightest object in the night sky?
The moon is the brightest object in the night sky.
Moon revolves around, which celestial body?
The moon revolves around the Earth.
Which celestial bodies revolve round the Sun?
Planets along with their satellites, comets, asteroids.
When did man land on the moon for the first time?
Man landed on the moon for the first time on July 21, 1969.
Who was the first human being to set foot on the moon?
Neil Armstrong was the first human being to set foot on the moon.
Who was the second astronaut who landed on the moon after Neil Armstrong?
Edwin Aldrin was the second astronaut who landed on the moon.
What is the speed of light in air?
The speed of light in air is 3 x 105 km per second.
Which direction do stars move?
Stars move from east to west.
Is there any change in the shape of the constellations?
The shape of the constellations does not change.
What is the other name of Orion?
The other name of the Orion is Hunter.
What does Cassiopeia look like?
Cassiopeia looks like a distorted letter W or M.
Planets shine like stars. Do planets have light of their own?
Although the planets shine like stars, but they do not have light of their own.
Do all planets have satellites?
Not all planets, but some of them have satellites.
Does Venus have moon?
Venus does not have moon or satellite of its own.
Name the only planet in the solar system which has life on its surface.
The Earth is the only planet in the solar system where life is known to exist.
What is called equatorial plane of the Earth?
The plane of the equator is called the equatorial plane of the Earth.
Which planet is the first outside from Earth (Orbit) in terms of distance from the Sun?
It is Mars.
Compare the mass of Jupiter with that of Earth.
Mars of Jupiter is about 318 times that of Earth.
Which is the largest planet of the solar system?
The largest planet of the solar system is Jupiter.
Does Jupiter have rings?
Yes, Jupiter has faint rings around it.
Name the outermost planets of the solar system.
Uranus and Neptune are the outermost planets of the solar system.
What is the other name of shooting star?
The other name of the shooting star is meteor.
Why was the village sky so different from the night sky in big cities?
Due to bright lights, smoke and other atmospheric pollution, a clear view of night sky in the big cities is rare, whereas it is possible in the village night sky.
What is meant by the term celestial object? What is the brightest object in the night sky?
The stars, the planets, the moon and many other objects in the sky are called celestial objects. The moon is the brightest object in the night sky.
What is the full moon day? What happens to the moon after full moon day?
The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter, every night the size, of the bright part of the moon decreases.
What is new moon day and the crescent moon?
On the fifteenth day after full moon day, the moon is not visible. This day is known as the new moon day.
The next day of new moon day, only a small part of the moon appears in the sky, which is called the crescent moon.
How many rotations are completed by the moon, when it completes one revolution?
The moon completes one rotation on its axis as it completes one revolution around the Earth.
Why do stars appear to us like points, whereas Sun looks bigger?
The stars are million times farther away than the Sun. That is why the stars appear to us like points. On the other hand, The Sun is nearer to the Earth than other stars, so the Sun looks bigger.
How far is the Sun from the Earth? Which is the next star nearest to the Earth?
The Sun is nearly 150,000,000 kilometres (150 million km) away from the Earth. The next nearest star to the Earth is the Alpha Centauri.
What is the distance of Alpha Centauri from Earth?
The next nearest star to the Earth after the Sun is Alpha Centauri, which is at a distance of about 40,000,000,000,000 km from the Earth.
Does the Pole star move? Is it a star or a planet?
The Pole star is not a planet. It is a star. The Pole star does not appear to move like other stars as it lies close to earth’s axis of rotation.
What is an orbit?
A planet has a definite path in which it revolves around the Sun. This path is called an orbit.
What is the period of revolution? What happens if distance of a planet from the Sun increases?
The time taken by a planet to complete one revolution is called it’s period of revolution. The period of revolution increases as the distance of the planet from the Sun increases.
What is the period of rotation?
The time taken by the planet to complete one rotation is called it’s period of rotation.
What is meant by the term satellite? What is moon?
A body revolving around another body is called a satellite. Generally, we use the term satellite for the bodies revolving around a planet. Moon is the natural satellite of the Earth.
What do you understand by natural satellite?
Any celestial body revolving around another celestial body is called its natural satellite.
What do you understand by artificial satellite?
There are many man-made satellites revolving round the Earth. These are called artificial satellites of the Earth.
What is unusual in the rotation of Venus?
The rotation of Venus on its axis is somewhat unusual. It rotates from east to west while the Earth rotates from west to east.
Why is Venus called a morning or an evening star?
Sometimes Venus appears in the eastern sky before sunrise. Sometimes it appears in the western sky just after sunset. That is why, it is often called a morning or an evening star, although it is not a star.
How is Venus observed in the sky?
Venus cannot be observed very high in the sky. It can be observed either 1-3 hours before sunrise’ or 1-3 hours after sunset.
Does Venus show phases like moon?
If Venus is observed through a telescope, it shows phases just like the moon.
Why does the Earth appear blue-green from space?
From space, the Earth appears blue and green due to the reflection of light from water and landmass on its surface.
Is axis of rotation of the Earth perpendicular to the plane of its orbit? How does the change of seasons take place?
The axis of rotation of the Earth is not perpendicular to the plane of its orbit.
The change of seasons on the Earth is caused due to tilted axis of rotation of Earth.
What are equatorial and orbital planes of the Earth?
The plane of the equator is called the equatorial plane of the Earth while the plane in which the Earth revolves round the Sun is called the orbital plane of the Earth.
Why is Mars called the red planet? How many natural satellites does Mars have?
Mars appears slightly reddish and, therefore, it is also called the red planet. Mars has two small natural satellites.
Which planets are called inner planets?
Mercury, Venus, Earth and Mars are much nearer to the Sun than the other planets. They are, therefore, called the inner or terrestrial planets.
(i) What is the angle (argument) between Earth’s equatorial of orbital plane?
(ii) What is the angle between earth’s axis and orbital plane?
What is light year? Which is nearest star to the sun and how far away it is?
Light year is the distance travelled by light in one year. Large distances in the space are measured in light years. The distance of the Sun from the Earth may be said to be about 8 light minutes.
The nearest star to the sun is Alpha Centauri. The distance of Alpha Centauri is about 4.3 light-years.
Write four uses of artificial satellites.
Uses of artificial satellites :
- They help in television and radio transmission.
- They help in telephonic communication.
- They help to study and forecast the weather by sending cloud pictures to the Earth, taken from space.
- They help in locating mineral elements by remote sensing (collecting information from distance).
- They help the scientists, to explore the universe in a better way. (Any four)
Describe the Sun in brief.
The Sun is the nearest star from us. It is continuously emitting huge amounts of heat and light. The Sun is the source of almost all energy on the Earth. In fact, the Sim is the main source of heat and light to all the planets that revolve around it.
How can you differentiate between planets and stars?
The simplest method of identifying planets from stars is that stars twinkle whereas planets do not. Also, they (planets) appear to change their positions with respect to the stars. A planet has a definite path (orbit) to revolve around the Sun. The stars do not have orbits.
What is meant by outer planets? Describe.
The planets outside the orbit of Mars, namely Jupiter, Saturn, Uranus and Neptune are much farther from the Sun than that the inner planets. So, they are called the outer planets. The masses and sizes of the outer planets are much larger than the masses and sizes of the inner planets. They have ring system around them. The outer planets have a large number of satellites.
(iv) Meteorites and
(v) Meteor showers.
(i) Asteroids: The large number of small objects that revolve around the Sun and occupy the large gaps between the orbits of Mars and Jupiter are called asteroids. These can be seen by large telescopes only.
(ii) Comets: They are also the members of our solar system. They revolve around the Sun in highly elliptical orbits. The period of their revolution around the Sun is very large.
The comet has a bright head with a long tail. The length of comet’s tail grows in size as it approaches the Sun. The tail of a comet is always directed away from the Sign. There are many comets which appear only after a definite time period. One of such comets is the Halley’s comet, which takes 76 years to reappear. It was last seen in 1986. The next time it will reappear in 2062.
(iii) Meteors: Bright streaks of light seen at night in the sky are called shooting stars or meteors. Meteors are usually small heavenly bodies which enters the Earth’s atmosphere with a very high speed, a friction is produced due to which the meteor heats up to such an extent that it burns out in a very short time. That is why the bright streak of light appears for a very short while.
(iv) Meteorites: Sometimes meteors are so large that a part of them reaches the surface of the Earth before they burn off completely. These are called meteorites. These help the scientists in investigating the nature of the material from which the solar system was formed.
(v) Meteor showers: When Earth crosses the tail of a comet, swarms of meteors are seen. These are known as meteor showers. Some meteor showers occur at regular times each year.
Write a brief note on the planet ‘Earth’.
Earth is the only planet in the solar system where life is known to exist. Life exists on Earth because Earth is situated just at the right distance from the Sun. Certain environmental conditions are also responsible for the existence and continuation of life on the Earth. These include presence of water and suitable atmosphere, right temperature range, and a blanket of ozone.
From the space, the Earth appears blue-green due to the reflection of light from water and landmass on its surface. The axis of rotation of the Earth is not perpendicular to the plane of its orbit. The change in seasons on the Earth is caused, due to this tilt. The Earth has only one satellite, namely moon. The equatorial plane and orbital plane of earth are inclined to each other at an angle of 23.5°. This means that the axis of the Earth is inclined to its orbital plane at and angle of 66.5°. So, the axis of the Earth makes an angle of 23.5° with the perpendicular to the orbital plane.
Multiple Choice Questions (MCQs)
1. Which one is not a part of solar system?