Textbook-based subjective questions

Nubra is a beautiful region in Ladakh.

The weather in Nubra is almost cloudless.

Night after night, Yangdol and Dorjay observe the stars and experience an Fig. 12.1: The beauty of night sky from a very dark immense sense of awe. location in Ladakh, India

They have heard how some particular stars in the clear skies helped the caravans passing through Nubra in finding direction in the ancient days. They wonder how far away and how big the stars are.

They also enjoy trying to find some patterns among the stars that remind them of familiar objects. Have you ever looked at the stars in the night sky and tried to connect them with imaginary lines, just like dots and lines in a drawing? 12.2 shows bright stars in one part of the night sky. Look at it carefully and try to imagine a pattern formed by a group of stars. Draw lines to connect the stars and make the pattern. Think of an animal or an object that is similar to the pattern drawn by you.

Write its name near your pattern. Repeat the above steps and make some more patterns. Now think of an interesting story about your patterns. Compare your patterns with the patterns drawn by your Narrate your story to others and listen to their stories.

Narrate your story to others and listen to their stories.

Some stars are bright and others Do we find patterns are dim.

Many cultures had names for patterns based on their own stories. These imaginary shapes helped them in recognising stars in the sky.

Recognising stars and their patterns was a useful skill for navigation in the olden times. Before the arrival of modern technology or even before the invention of the magnetic compass, it helped people, particularly sailors and travellers, in finding directions at sea or on land.

In earlier times, groups of stars forming patterns were called constellations. Currently, the term constellation refers to defined regions of the sky that often include these patterns of stars. However, as the patterns of stars are often the most noticeable feature, the term constellation is still commonly used for these groups of stars.

However, as the patterns of stars are often the most noticeable feature, the term constellation is still commonly used for these groups of stars. Since different cultures denoted the constellation boundaries in different ways, an internationally agreed set of constellation boundaries were defined by the International Astronomical Union (IAU) in the early twentieth century. 88 constellations were officially listed, thus, dividing the entire sky into 88 regions.

More to These regions of sky are now defined as constellations. know!

The constellation Orion is often represented as a hunter.

12.3: Some constellations and stars (The red lines indicate the patterns of stars while the green lines indicate the regions of the sky. The lines are not seen in the sky and have been drawn only for easy identification)

In Indian astronomy, the term nakṣhatra is used to denote either a certain star or a group of stars, such as Ārdrā (a star called Betelgeuse in the Orion constellation) and Kṛittikā (a group of stars called Pleiades in the Taurus constellation). Aldebaran, a star in the constellation More to Taurus, is known as Rohiṇī.

The Pole Star or Polaris, which is part of the Little Dipper is also shown (Fig. The Pole Star appears nearly stationary in the North direction. This helps to locate the North direction in the Northern hemisphere.

Big Dipper The Big Dipper lies in the constellation Ursa Major while the Little Dipper lies in the constellation Ursa Minor. In India, the Big Dipper is known as Saptaṛiṣhi, and the Little Pole Star is known as Dipper Dhruva tārā. 12.4: Big Dipper, Little Dipper How can and Pole Star (The lines are not seen we identify in the sky and have been drawn only for easy identification) some of these constellations in the night sky? sociated fr om co m m on regional stories as Apa rt any forest st ar s in th e constellations, m with so have g co m m un iti es or tribes of India al dwel lin ple, the r ow n st or ie s ab out them.

12.4: Big Dipper, Little Dipper How can and Pole Star (The lines are not seen we identify in the sky and have been drawn only for easy identification) some of these constellations in the night sky? sociated fr om co m m on regional stories as Apa rt any forest st ar s in th e constellations, m with so have g co m m un iti es or tribes of India al dwel lin ple, the r ow n st or ie s ab out them.

12.2 Night Sky Watching If it is a clear cloudless night, a large number of stars may be visible in the sky.

This is due to light pollution, smoke and dust. The presence of excessive artificial light at night time is referred to as light pollution.

Also, your house may be surrounded by tall buildings and trees, which may block your view. The night sky is best viewed from open dark areas.

Light pollution is growing sharply globally. This is reducing our ability to enjoy and study objects in the night sky. Some dark sky reserves and parks have been established around the world.

Light pollution in the reserves is controlled to preserve dark skies for research. There are organisations which are working to educate people Do you about reducing light pollution. know? Not all stars and constellations are visible from all places on Earth and on all nights in a year.

Can we try to find For example, the Pole Star is not visible from any constellation the southern hemisphere of Earth.

To get familiar with the pattern of a constellation

The More to computer version of Stellarium is free for know! download and has many features. Preparation for night sky watching Under the guidance of adults, identify a dark open area for night sky watching.

This should be away from lights, tall buildings and trees. With the help of an app, choose the date and time based upon what you plan to identify in the night sky. Choose a night where neither the Moon nor the clouds are visible particularly for identifying the Pole Star which is not very bright. It may be useful to have access to a mobile app with a map of the sky, or print out images of the constellations you plan to view. You may also carry a magnetic compass to find directions and a notebook to note or draw your observations. On the particular day and time selected, go to the Caution identified place with an adult, where the night sky Do not go to a dark open place watching is to be done. at night time After reaching there, wait for about half an hour for without adults accompanying you. your eyes to get adjusted to the darkness.

Activity 12.2: Let us try to locate Look for the Big Dipper during summer time in the early part of the night, say, around 9 p.m. View the sky towards the northern part of the sky and identify the Big Dipper. Once you identify the Big Dipper, try to locate the Pole Star. Look at the two stars present at the end of the Big Dipper’s cup and imagine a straight line passing through these towards the north.

Look at the two stars present at the end of the Big Dipper’s cup and imagine a straight line passing through these towards the north. At about five times the distance between these two stars, the imaginary line will lead to another star which is not very bright. You may also locate the bright constellation Orion and the star Sirius in the night sky.

Activity 12.3: Let us try to identify In India, Orion is best viewed during the months of December to April after sunset.

12.3 Our Solar System The Sun The Sun is a star.

The Sun gives out a huge amount of energy, and that is why it glows so brightly. The Sun produces heat and light, and is the main source of energy on the Earth (Fig.

And still, it looks so small because it is very far from the Earth. The distance of the Sun from the Earth is about 150 million km.

A useful unit for expressing distances within the solar system is ‘astronomical unit’ (au) which is approximately the distance between the Sun and the Earth. Our the brightest The Sun, being Sun is also a source of light object and the most star. So how is it that t on E ar th , was elevated in the Sun appears big and and h ea a deity. t ci vi li za ti on s to the status of lights up the sky while the ancien rya.

The other stars look like bright ia , th e Su n is w orshipped as Sū In Ind the Earth dots in the night sky and p ro vi d ed b y the Sun keeps heat ossible. are not even visible er at u re th at makes life p at a te m p to grow, during the day time? gh t is es se n ti al for plants Sunli animals, p ro vi d e fo od and oxygen to which sible for d in g h u m an s. The Sun is respon inclu cle, e, se as on s, w eather, water cy climat r al l of w h ic h are important fo wind s— the Earth. sustaining life on Beyond Earth However, the Sun is much closer to us than the other stars hence it appears much bigger than the stars.

However, the Sun is much closer to us than the other stars hence it appears much bigger than the stars.

The star nearest to us after the Sun is Proxima Centauri which lies at a distance of about 269000 au.

There are many more objects Are stars the only in the sky. Our Earth, along objects in the sky? with some of these objects, Or, are there more and the Sun together form objects which our Solar System (Fig.

The movement of an object around the Sun is called revolution. Planets A planet is a large, nearly spherical object that revolves around the Sun.

The Earth takes nearly one year to complete one revolution. Like the Earth, there are other planets that revolve around the Sun. While revolving around the Sun, the Earth is also rotating about its axis.

While revolving around the Sun, the Earth is also rotating about its axis. For one full rotation, the Earth takes about 24 hours which is called a day. Like the Earth, other planets also rotate about their axes while revolving around the Sun.

You More to will learn more about this in the next Grade. know!

The eight planets, in order of their increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (Fig.

From ancient times, various names have been used across India for the planets visible to the naked eye. For example, Budha (Mercury), Śhukra (Venus), Beyond Earth

Pṛithvī (Earth), Mangala (Mars), Bṛihaspati or Guru (Jupiter) and Śhani (Saturn). Venus is usually seen shining brightly at dawn and dusk, and is commonly called the Morning Star or the Evening Star, even though it is not a star.

This is because the soil on Mars is reddish in colour. A large portion of the Earth’s surface is covered with water and thus, it appears blue from the space. Due to this, the Earth is also called the Blue Planet.

The four outermost planets—Jupiter, Saturn, Uranus and Neptune—are much larger compared to the Earth, and are mostly made of gas and ice. These giant planets have large flat ring-like structures around them which are made of dust particles and rocky material. Planets get most of their energy from the Sun.

Planets get most of their energy from the Sun.

That is why Venus, for example, is hotter than Mercury, although it is farther from the Sun.

When it was discovered, it was called a planet of the Solar System. But later, when similar more small objects were discovered, the International Astronomical Union (IAU) in 2006 redefined the requirements of an object to be called a planet.

Among the planets, it is fy i d enti easiest to identify Venus we so, Can lanet al e which is very bright. After a p way w e the Sun and the Moon, Venus the fied th ? is the brightest object in the ti s iden ellation sky.

Mercury, Mars, Jupiter st con and Saturn can also be seen with the naked eye. so far away that they look like shining dots, just like stars. So how can we distinguish between planets and the stars?

Unlike planets, the stars appear to twinkle a lot. Activity 12.4: Let us try to identify With the help of an app, Venus can be located either at dawn or at dusk. How can we When you are viewing at dawn, see the planets which are not look for it near the Eastern visible to the direction before sunrise. naked eye? When you are viewing at dusk, look for it near the Western direction after sunset.

While many of the objects in the sky can be seen with our naked eyes directly, we can see them brighter and larger using a pair of binoculars or an instrument called a telescope (Fig.

You may get an opportunity to view the sky through a telescope whenever a night sky watching event is organised in your region.

There are around the Sun. many Amateur Astronomy Are there any Clubs all over the objects that move country which around planets? organise sky watching events periodically. Natural Satellites Objects that move around planets are commonly called satellites.

They are smaller in size than planets. Moons are natural satellites of planets.

Jupiter, Saturn, Uranus and Neptune have a large number of moons. The Moon In general, any object Earth’s natural satellite, the Moon, that moves around a takes about 27 days to complete much larger object can one revolution around the Earth. also be called a satellite. It is our nearest neighbour in the For example, Earth can space.

It is our nearest neighbour in the For example, Earth can space. Unlike on the Earth, there be considered is hardly any atmosphere on a satellite of the Moon. How big is the Moon the Sun. as compared to the Earth?

The Moon is about a quarter the size More to of the Earth in diameter.

12.9: The Moon (a) Image taken by Cartosat, ISRO.

atmosphere, water or life on the Moon, these features stay on the Moon’s surface for a very long time. Although the Moon is very far, humans have sent spacecrafts to explore and understand more about the Moon.

To improve our understanding of the Moon, India’s first mission to the Moon, Chandrayaan-1, was launched in 2008 and the second mission, Chandrayaan-2, in 2019. The third mission, Chandrayaan-3, was launched in July 2023 and its Vikram lander carrying the Pragyan rover successfully soft-landed on the Moon on 23 August 2023.

With this mission, India became the first country in the world to achieve a landing near the little explored Moon’s south pole. To mark this success, the Government of India declared 23 August to be celebrated as ‘National Space Day’ in India. Do you A fourth mission, Chandrayaan-4, is being planned which know? aims to bring back soil and rock samples from the Moon.

Asteroids The Sun and the planets are nearly spherical in shape. There are many small objects in the Solar System which are rocky and irregular in shape. Many of these asteroids revolve around the Sun in paths that lie between those of Mars and Jupiter.

Many of these asteroids revolve around the Sun in paths that lie between those of Mars and Jupiter.

Sometimes we have visitors from the outer regions of the Solar System!

As a comet approaches close to the Sun, the frozen material in it starts evaporating. Comets appear dim as they move away from the Sun and then, it is not possible to see them with the naked eye.

These comets approach close to the Sun periodically. However, there are a few comets that escape and move out of the Solar System.

We have learnt about the objects which form the Solar One famous comet is the System. Halley’s Comet which appears The Sun, eight planets, their every 76 years. Its last moons, and many smaller appearance was in 1986. objects including asteroids, and comets, together form the Solar System.

Its last moons, and many smaller appearance was in 1986. objects including asteroids, and comets, together form the Solar System. The Sun—our star—is the In Sanskrit and a few other Indian More to largest and the heaviest object in the Solar System. The Sun languages, a comet know! produces almost all the energy in is called Dhūmaketu. the Solar System.

All other objects Various tribes in India also call it Pucchya-Taro in our Solar System shine due to (star with a tail) or Zendya- the sunlight that they reflect from

In many cultures, comets have been feared and it was earlier believed that comets bring What is bad luck.

This is our home galaxy called the Milky Way Galaxy or Ākāśha Gangā. A galaxy has millions to billions of stars.

Our Solar System is part of the Milky Way Galaxy. 12.5 The Universe What is beyond the There are many galaxies in the Milky Way outer space beyond the Milky Galaxy?

We do not know yet if life exists Is there life elsewhere in the Universe. The search anywhere for life has been directed mostly towards else in the exoplanets—the planets discovered Universe? revolving around other stars in our Beyond Earth Till now, scientists have not found any evidence of life but this search is on and continuing.

The sky is divided into regions called constellations, which include groups of stars that appear to form patterns. The Pole Star appears nearly stationary in the North direction. This helps in locating the North direction in the Northern hemisphere. The Sun is a star which produces heat and light. A planet is a large, nearly spherical object that revolves around the Sun. The eight planets, in order of their increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The Earth revolves around the Sun in nearly one year. Objects that move around planets are commonly called satellites. The Moon is Earth’s natural satellite. The Moon revolves around the Earth in nearly 27 days. The Sun, eight planets, their moons, and many smaller objects including asteroids and comets, together form the Solar System. Our Solar System is part of the Milky Way Galaxy.

The eight planets, in order of their increasing distance from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The Earth revolves around the Sun in nearly one year. Objects that move around planets are commonly called satellites. The Moon is Earth’s natural satellite. The Moon revolves around the Earth in nearly 27 days. The Sun, eight planets, their moons, and many smaller objects including asteroids and comets, together form the Solar System. Our Solar System is part of the Milky Way Galaxy.

(ii) Make two similar riddles by yourself.

(i) Sirius (ii) Comets (iii) Asteroids (iv) Pluto Which of the following is not a planet of the Sun?

Which is the brighter star, the Pole Star or Sirius? An artist’s representation of the Solar System is given in Fig.

If not, write the correct order in the boxes in the figure. A portion of night sky with stars is shown in Fig. Look carefully and identify the groups

of stars that form the patterns—the Big Dipper and the Little Dipper. Draw lines to connect the stars for these patterns and label them. Also, identify and label the Pole Star.

A portion of the night sky is shown in Fig.

From Earth, you can see stars fading away at dawn and appearing at dusk.

Also try to locate the Pole Star each time. Draw a rough sketch to illustrate this, mentioning the time in each case.

Try to find out the names of planets in your local language. Also, find out the stories associated with stars and constellations in your region.

If there is a planetarium or a science museum nearby, then Beyond Earth you can visit it, especially if a night sky observation session is scheduled by them. You will get to see the Moon, the planets and the stars through a telescope.

You will get to see the Moon, the planets and the stars through a telescope. If you visit the planetarium during daytime, you can also see their models, pictures and sky shows. Find out if the increasing light pollution is causing problems for humans, wildlife and the environment.

Write an action that you would take at the personal level to control light pollution. Find out the weather conditions due to which the Indian Institute of Astrophysics (IIA) found Hanle, Ladakh a suitable place to set up an observatory. If you enjoy doing embroidery, try to embroider on a dark coloured cloth the constellations that you have seen (Fig.

12.15: Embroidery in multiple other ways using various art and of constellations craft ideas.

One of them is called the Himalayan Chandra Telescope, which has been named after the Nobel Prize winning scientist Subrahmanyan Chandrasekhar. It is an observatory at one of the highest locations in the world.

open to the public throughout the year. Local people have been provided with small telescopes and are trained to be Astronomy Ambassadors for visitors by the Indian Institute of Astrophysics.

It is expected to promote astro-tourism in the region. This might be the last page of this book, but it is certainly not the end of our ‘Curiosity’. The title of this book not only drives our journey through the amazing world of science, but also defines what it means to be human.

We want to find out more about the world we live in and worlds beyond. By now, you have perhaps read a little bit about the world of plants and animals, done some fun activities, learnt about how we measure, wondered about the stars that shine in the night sky, and so on. But remember, this is just the beginning.

But remember, this is just the beginning.

The key lies in that curiosity you have nurtured throughout this journey.

Remember, even the most groundbreaking discoveries often begin with a simple “Why?”. There are countless questions waiting to be answered, and countless answers waiting to be questioned.

You, my young scientist, can find them out. And see you again in the next Grade for more adventures in science!