Beyond Earth

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A–5, B–1, C–4, D–2, E–3

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Constellations are groups of stars that appear to form patterns, like shapes of familiar things. Currently, the term refers to defined regions of the sky that include these patterns.

88 constellations were officially listed by the International Astronomical Union (IAU) in the early twentieth century, dividing the entire sky into 88 regions.

Orion is represented as a hunter. The three stars in the middle represent the belt of the hunter.

Sirius is the brightest star in the night sky, and it belongs to the constellation Canis Major.

Betelgeuse = Ārdrā (in Orion); Pleiades = Kṛittikā (in Taurus); Aldebaran = Rohiṇī (in Taurus).

The Pole Star (Polaris) appears nearly stationary in the North direction. It helps to locate the North direction in the Northern hemisphere.

The Big Dipper is known as Saptaṛiṣhi (in Ursa Major), and the Pole Star is known as Dhruva tārā.

Light pollution is the presence of excessive artificial light at night. It reduces the number of stars visible and our ability to enjoy and study the night sky; fewer stars are seen in cities due to light pollution, smoke and dust.

Sky Map and Stellarium are apps used for identifying stars, constellations and planets.

The Sun is a star—the star closest to us, an extremely hot spherical ball of gases. It appears bigger than other stars because it is much closer to us than the other stars.

An astronomical unit (au) is a unit for expressing distances within the solar system; it is approximately the distance between the Sun and the Earth.

Proxima Centauri is the nearest star after the Sun, lying at a distance of about 269000 au.

A planet is a large, nearly spherical object that revolves around the Sun. The Earth is a planet.

Revolution is the movement of the Earth around the Sun (taking about one year). Rotation is the spinning of the Earth about its axis (taking about 24 hours, called a day).

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Venus is usually seen shining brightly at dawn and dusk, so it is commonly called the Morning Star or the Evening Star, even though it is not a star.

Mars appears red because its soil is reddish in colour. The Earth appears blue from space because a large portion of its surface is covered with water.

Jupiter, Saturn, Uranus and Neptune are much larger than the Earth and are mostly made of gas and ice; they have large flat ring-like structures of dust and rocky material.

When Pluto was discovered it was called a planet, but later when similar small objects were found, the IAU in 2006 redefined the requirements for a planet. Pluto and these smaller objects are now called dwarf planets.

The Moon is Earth's natural satellite and our nearest neighbour in space. It takes about 27 days to complete one revolution around the Earth.

Introduction: Long ago, watching the night sky was a favourite pastime, and our ancestors identified patterns among the stars.
Key Points:
1. Identifying patterns — Some groups of stars appeared to form shapes of familiar animals, things or story characters.
2. Different names — Many cultures gave the star patterns their own names based on their own stories.
3. Use in navigation — Recognising stars and their patterns helped sailors and travellers find directions before the compass was invented.
Conclusion: Constellations helped people recognise stars in the sky, and star patterns are still used as a backup method in emergencies.

Introduction: Orion is a well-known constellation often represented as a hunter, with related constellations and bright stars near it.
Key Points:
1. The hunter — Orion is imagined as a hunter, with three middle stars representing the belt of the hunter.
2. Canis Major and Sirius — Canis Major, the hunter's dog, contains Sirius, the brightest star in the night sky.
3. Taurus and nakshatras — Taurus is imagined as a bull; Betelgeuse is called Ārdrā, Aldebaran is Rohiṇī, and Pleiades is Kṛittikā.
Conclusion: In India, Orion is best viewed from December to April after sunset, making it easy to identify in the night sky.

Introduction: The Big Dipper and Little Dipper are two well-known star patterns, and the Pole Star lies in the Little Dipper.
Key Points:
1. Big Dipper — It is a distinct pattern of stars that lies in the constellation Ursa Major.
2. Little Dipper — It is another star pattern that lies in the constellation Ursa Minor.
3. Pole Star — The Pole Star (Polaris) is part of the Little Dipper and appears nearly stationary in the North.
Conclusion: In India, the Big Dipper is known as Saptaṛiṣhi and the Pole Star is known as Dhruva tārā.

Introduction: The Pole Star is not very bright, but it can be easily located with the help of the Big Dipper.
Key Points:
1. Find the Big Dipper — Look towards the northern part of the sky in early summer nights to spot the Big Dipper.
2. Use the cup stars — Look at the two stars at the end of the Big Dipper's cup.
3. Draw the line — Imagine a straight line through them towards the north, about five times the distance between them.
Conclusion: This imaginary line leads to the Pole Star, which helps us locate the North direction.

Introduction: The Sun is the star closest to us, an extremely hot spherical ball of gases that glows brightly.
Key Points:
1. The Sun is a star — It produces a huge amount of heat and light energy, which is why it glows so brightly.
2. Its size and distance — The Sun is about 100 times bigger than the Earth in diameter and about 150 million km away.
3. Why sizes look different — The Sun appears big because it is nearest to us; other stars are so far away that they appear as bright dots.
Conclusion: Even though some stars are much bigger than our Sun, their great distance makes them look like points.

Introduction: The eight planets of the Solar System are divided into inner and outer planets based on their distance from the Sun.
Key Points:
1. Inner planets — Mercury, Venus, Earth and Mars are the four planets nearest to the Sun.
2. Nature of inner planets — They are smaller in size and have solid surfaces with rocks on them.
3. Outer planets — Jupiter, Saturn, Uranus and Neptune are the four outermost planets.
4. Nature of outer planets — They are much larger than the Earth, made mostly of gas and ice, and have ring-like structures.
Conclusion: The inner planets are small and rocky, while the outer planets are giants of gas and ice with rings.

Introduction: Generally, planets farther from the Sun are colder, but Venus is an exception to this rule.
Key Points:
1. General rule — Planets get most of their energy from the Sun, so farther planets are usually colder.
2. Venus's atmosphere — Venus has an atmosphere that can trap heat.
3. Trapped heat — This trapped heat significantly raises the temperature of Venus above that of Mercury.
Conclusion: The heat-trapping atmosphere of Venus makes it hotter than Mercury even though it is farther from the Sun.

Introduction: The Moon is the Earth's natural satellite and our nearest neighbour in space.
Key Points:
1. Basic facts — The Moon is about 3,84,000 km away and takes about 27 days to revolve around the Earth.
2. Size and atmosphere — It is about a quarter the size of the Earth and has hardly any atmosphere.
3. Craters — Its surface shows circular bowl-like structures called craters, formed by the impact of asteroids and rocks.
Conclusion: Since there is no atmosphere, water or life on the Moon, its surface features stay unchanged for a very long time.

Introduction: Asteroids are small rocky objects that are part of our Solar System along with the planets.
Key Points:
1. What they are — Asteroids are small objects that are rocky and irregular in shape.
2. Where they are found — Many asteroids revolve around the Sun in paths that lie between Mars and Jupiter, called the asteroid belt.
3. Their sizes — The sizes of asteroids range from about 10 m to about 500 km.
Conclusion: Occasionally, some asteroids pass very close to the Earth as they revolve around the Sun.

Introduction: Comets are icy-rocky visitors from the outer regions of the Solar System that have long tails.
Key Points:
1. What comets are — Comets are made up of dust, gases, rocks and ice.
2. How the tail forms — As a comet approaches close to the Sun, its frozen material starts evaporating, forming the tail.
3. Their brightness — Comets appear dim as they move away from the Sun and then cannot be seen with the naked eye.
Conclusion: Halley's Comet is a famous comet that appears every 76 years; in Sanskrit, a comet is called Dhūmaketu.

Introduction: Our Solar System is made up of the Sun and many objects that move around it.
Key Points:
1. Main members — The Sun, the eight planets and their moons together form the Solar System.
2. Smaller objects — Many smaller objects, including asteroids and comets, are also part of it.
3. Revolution — Most of these objects move around the Sun, and this movement is called revolution.
Conclusion: The Sun is the largest and heaviest object of the Solar System and produces almost all its energy.

Introduction: Beyond our Solar System lies our home galaxy, the Milky Way, and beyond it, the vast Universe.
Key Points:
1. The Milky Way — On moonless nights, a faint band of light seen across the sky is our galaxy, the Milky Way.
2. Its Indian name — The Milky Way Galaxy is known in India as Ākāśha Gangā.
3. What a galaxy is — A galaxy has millions to billions of stars, and our Solar System is part of the Milky Way Galaxy.
4. The Universe — There are many galaxies in outer space beyond the Milky Way, and together they make up the Universe.
Conclusion: Scientists study these galaxies to understand the stars, galaxies and the Universe.

Introduction: India has launched three Chandrayaan missions to explore and understand the Moon, with a fourth planned.
Key Points:
1. Chandrayaan-1 and 2 — India's first Moon mission, Chandrayaan-1, was launched in 2008, and Chandrayaan-2 in 2019.
2. Chandrayaan-3 — Launched in July 2023, its Vikram lander with the Pragyan rover soft-landed on the Moon on 23 August 2023.
3. A world first — With this landing near the Moon's south pole, India became the first country in the world to do so.
Conclusion: 23 August is now celebrated as National Space Day, and Chandrayaan-4 is planned to bring back Moon samples.

Introduction: Planets look like shining dots, just like stars, but there are ways to tell them apart.
Key Points:
1. Twinkling — Unlike planets, the stars appear to twinkle a lot in the night sky.
2. Steady shine — Planets shine steadily, which helps us distinguish them from twinkling stars.
3. Use of a telescope — A telescope shows objects brighter and larger, and helps us view dim objects not visible to naked eyes.
Conclusion: With binoculars or a telescope, we can see many sky objects that our naked eyes cannot see directly.

Introduction: Night sky watching needs careful preparation to be enjoyable and safe for everyone.
Key Points:
1. Choose the place — With adults, identify a dark open area away from lights, tall buildings and trees.
2. Choose the night — Use an app to pick the date and time; choose a night without Moon or clouds.
3. Carry the aids — Carry a sky map app or printed images, a magnetic compass and a notebook.
4. Eye adjustment — After reaching, wait about half an hour for your eyes to adjust to the darkness.
Conclusion: Never go to a dark open place at night without adults accompanying you — safety comes first.

(a) The weather is almost cloudless with almost no air or light pollution. (b) Constellations. (c) Star patterns helped sailors and travellers find directions for navigation before the magnetic compass; they are still used as a backup. 88 constellations were officially listed by the IAU.

(a) Orion. (b) Sirius, in the constellation Canis Major. (c) Betelgeuse = Ārdrā (in Orion); Pleiades = Kṛittikā (in Taurus).

(a) The Pole Star (Polaris). (b) Big Dipper—Ursa Major; Little Dipper—Ursa Minor. (c) Big Dipper = Saptaṛiṣhi; Pole Star = Dhruva tārā. The Pole Star appears nearly stationary in the North direction and helps locate the North direction in the Northern hemisphere.

(a) Because the Sun is much closer to us than the other stars. (b) An astronomical unit (au) is approximately the distance between the Sun and the Earth. (c) During daytime, the extreme brightness of the Sun makes it impossible to view other stars. The nearest star after the Sun is Proxima Centauri (about 269000 au away).

(a) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. (b) Inner four (Mercury, Venus, Earth, Mars) have solid rocky surfaces; outer four (Jupiter, Saturn, Uranus, Neptune) are mostly gas and ice. (c) Venus's atmosphere traps heat, making it hotter than Mercury; the Earth is called the Blue Planet because a large part of its surface is covered with water and it appears blue from space.

(a) About 27 days. (b) Craters are circular bowl-like structures on the Moon's surface, formed due to the impact of asteroids or rocks from space hitting the surface. (c) Because there is hardly any atmosphere, water or life on the Moon, nothing wears away the features quickly, so they stay for a very long time.

(a) Vikram lander and Pragyan rover. (b) India became the first country in the world to achieve a landing near the Moon's south pole. (c) 23 August is celebrated as National Space Day. Chandrayaan-4 aims to bring back soil and rock samples from the Moon.

(a) Dust, gases, rocks and ice. (b) As a comet approaches close to the Sun, the frozen material in it evaporates, forming the tail. (c) Halley's Comet appears every 76 years (last seen in 1986). As comets move away from the Sun, the evaporating stops and they appear dim, so they cannot be seen with the naked eye.

(a) The Sun, eight planets, their moons, and many smaller objects including asteroids and comets. (b) Ākāśha Gangā. (c) The Sun is the largest and heaviest object in the Solar System and produces almost all the energy in it. All other objects shine due to the sunlight they reflect from their surfaces.

(a) During daytime, the extreme brightness of the Sun makes it impossible to view other stars from Earth. (b) A telescope. (c) (i) Identify a dark open area away from lights, tall buildings and trees, and go only with an adult. (ii) Choose a clear, cloudless, moonless night (especially for the faint Pole Star) and wait about half an hour for your eyes to adjust to the darkness.

Introduction: The night sky is full of stars, and groups of them form patterns that people have named constellations.
Key Points:
1. Stars — Stars shine with their own light; some are bright and others are dim.
2. Constellation patterns — Some groups of stars appear to form shapes like familiar animals, things or story characters.
3. Naming by cultures — Long ago, ancestors identified these patterns, and many cultures named them after their own stories.
4. Division of the sky — The International Astronomical Union defined 88 constellation boundaries, dividing the entire sky into 88 regions.
5. Why they were useful — Recognising star patterns helped sailors and travellers find directions before the magnetic compass was invented.
Conclusion: Constellations are still used to recognise stars in the sky and as a backup method of navigation in emergencies.

Introduction: Orion is a bright constellation represented as a hunter, with several stars and constellations linked to it.
Key Points:
1. The hunter's belt — Orion is imagined as a hunter; three bright stars in a straight line form its belt.
2. Canis Major and Sirius — The hunter's dog, Canis Major, contains Sirius, the brightest star in the night sky.
3. Taurus — Some people imagine the hunter battling a bull, which is the constellation Taurus.
4. Nakshatra names — Betelgeuse in Orion is Ārdrā; Aldebaran in Taurus is Rohiṇī; the Pleiades group in Taurus is Kṛittikā.
5. Locating Sirius — A straight line through Orion's three belt stars, extended towards the east, leads to Sirius.
Conclusion: Orion is best viewed in India from December to April after sunset, and its belt is the easiest way to find it.

Introduction: The Sun is the star closest to us, and along with the planets and other objects, it forms our Solar System.
Key Points:
1. The Sun is a star — It is an extremely hot spherical ball of gases that gives out huge amounts of heat and light energy.
2. Size and distance — The Sun is about 100 times bigger than the Earth in diameter and about 150 million km away.
3. What a planet is — A planet is a large, nearly spherical object that revolves around the Sun.
4. The eight planets — In order of increasing distance, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
5. Earth's movements — The Earth takes nearly one year for one revolution around the Sun and about 24 hours for one rotation.
Conclusion: The Sun is the main source of energy on the Earth, and most objects of the Solar System revolve around it.

Introduction: The Moon is the Earth's natural satellite, and India has sent three missions to explore it.
Key Points:
1. Basic facts — The Moon is about 3,84,000 km from the Earth and takes about 27 days to revolve around it.
2. Size and atmosphere — It is about a quarter of the Earth's diameter and has hardly any atmosphere.
3. Craters — Circular bowl-like craters formed by asteroid and rock impacts stay long because there is no atmosphere, water or life.
4. Chandrayaan-1 and 2 — India's first Moon mission was launched in 2008 and the second in 2019.
5. Chandrayaan-3 — Its Vikram lander with the Pragyan rover soft-landed near the Moon's south pole on 23 August 2023, a world first.
Conclusion: 23 August is now National Space Day in India, and Chandrayaan-4 is planned to bring back soil and rock samples.

Introduction: Asteroids, comets and natural satellites are different kinds of smaller objects found in the Solar System.
Key Points:
1. Asteroids — These are small rocky objects of irregular shape, from about 10 m to 500 km across.
2. Asteroid belt — Many asteroids revolve around the Sun between the paths of Mars and Jupiter.
3. Comets — Comets are made of dust, gases, rocks and ice, and develop long tails when they approach the Sun.
4. Halley's Comet — It is a famous comet that appears every 76 years; its last appearance was in 1986.
5. Natural satellites — Moons are natural satellites of planets; the Earth has one Moon, Mars has two, and the outer planets have many.
Conclusion: These objects, together with the Sun, the planets and their moons, form the Solar System.

Introduction: The Sun is a star like the others, but it looks very different in our sky because of its distance.
Key Points:
1. The Sun is nearest — The Sun is the star closest to us, at about 150 million km from the Earth.
2. Why it appears big — Being much closer than other stars, the Sun appears much bigger and lights up the sky.
3. Why stars appear as dots — Other stars are so far away that they appear like points, though some are bigger than our Sun.
4. Nearest star after the Sun — Proxima Centauri lies at about 269000 times our distance to the Sun.
5. Stars during the day — During daytime, the extreme brightness of the Sun makes it impossible to view other stars from Earth.
Conclusion: The Sun's nearness makes it appear big and bright, while its glare hides the other stars during the day.

Introduction: The eight planets are divided into four inner and four outer planets with very different features.
Key Points:
1. Inner planets — Mercury, Venus, Earth and Mars are smaller and have solid surfaces with rocks on them.
2. Venus — It shines brightly at dawn and dusk and is called the Morning or Evening Star; its atmosphere traps heat, making it hotter than Mercury.
3. Mars — Mars is called the Red Planet because its soil is reddish in colour.
4. The Earth — A large portion of its surface is covered with water, so it appears blue from space and is called the Blue Planet.
5. Outer planets — Jupiter, Saturn, Uranus and Neptune are much larger, made mostly of gas and ice, and have flat ring-like structures.
Conclusion: The inner planets are small and rocky, while the outer ones are giant, gaseous and ringed.

Introduction: Light pollution and city conditions hide most stars, so night sky watching needs careful planning.
Key Points:
1. What light pollution is — The presence of excessive artificial light at night time is called light pollution.
2. Its effect — In cities, light pollution, smoke and dust hide the stars; dark sky reserves are being set up to preserve dark skies.
3. Choosing the place — With adults, identify a dark open area away from lights, tall buildings and trees.
4. Choosing the night and aids — Pick the date and time with an app, choose a Moon-free, cloudless night, and carry a sky map, compass and notebook.
5. Eye adjustment and safety — Wait about half an hour for your eyes to adjust to darkness, and never go out at night without adults.
Conclusion: Good preparation and safety precautions make night sky watching both successful and enjoyable.

Introduction: Our Solar System lies in the Milky Way Galaxy, which is just one among many galaxies in the Universe.
Key Points:
1. The Milky Way — On moonless nights from dark places, a faint band of light across the sky is our home galaxy.
2. Its Indian name — The Milky Way Galaxy is known as Ākāśha Gangā in India.
3. What a galaxy contains — A galaxy has millions to billions of stars, and our Solar System is part of the Milky Way Galaxy.
4. The Universe — There are many galaxies beyond the Milky Way, and scientists study them to understand the Universe.
5. Search for life — The search is directed mostly towards exoplanets, planets revolving around other stars; no evidence of life has been found yet.
Conclusion: The search for life elsewhere in the Universe is still on and continuing.

Introduction: The Solar System is a family of objects bound together by the Sun, its largest member.
Key Points:
1. Members of the Solar System — The Sun, eight planets, their moons, and smaller objects including asteroids and comets form the Solar System.
2. Revolution — Most of these objects move around the Sun, and this movement is called revolution.
3. The Sun's size — The Sun is the largest and the heaviest object in the Solar System.
4. The Sun's energy — It produces almost all the energy in the Solar System.
5. Why others shine — All other objects in the Solar System shine due to the sunlight they reflect from their surfaces.
Conclusion: The Sun's heat and light sustain life on Earth and control the movement of every object in the Solar System.