- (a) Tycho Brahe
- (b) Nicolaus Copernicus
- (c) Ptolemy
- (d) Archimedes
Answer:
(b) Nicolaus Copernicus
- (a) Mercury
- (b) Saturn
- (c) Uranus
- (d) Neptune
Answer:
(a) Mercury
- (a) meteor
- (b) star
- (c) planet
- (d) asteroid
Answer:
(d) asteroid
Ceres is also classified as a dwarf planet.
- (a) 4
- (b) 5
- (c) 2
- (d) 3
Answer:
(a) 4
Using Kepler’s Third Law:
- (a) 13.7 billion years ago
- (b) 15 million years ago
- (c) 15 billion years ago
- (d) 20 million years ago
Answer:
(a) 13.7 billion years ago
Modern estimate is approximately 13.8 billion years.
- Speed of the Sun around the Milky Way is about 250 km/s.
- Rotational period of the Sun near poles is about 36 days.
- India’s first satellite was Aryabhata.
- Kepler’s third law is also called Law of Harmonics.
- Number of planets in Solar System is 8.
If false, correct the statement.
Answer: True
Answer: False
Correct Statement:
Halley’s comet appears approximately every 76 years.
Answer: False
Correct Statement:
Satellites nearer Earth require greater orbital velocity.
Answer: True
Answer:
The Sun and all celestial bodies revolving around it together form the Solar System.
It includes:
- planets
- satellites
- asteroids
- comets
- meteors
Answer:
Orbital velocity is the horizontal velocity required for a satellite to revolve around Earth in circular orbit.
Answer:
Time taken by satellite to complete one revolution around Earth is called orbital period.
Answer:
A body revolving around a planet is called satellite.
Types:
- Natural satellites
- Artificial (man-made) satellites
Answer:
Inner planets are planets close to Sun.
They are:
- Mercury
- Venus
- Earth
- Mars
Features:
- Rocky planets
- High density
- Smaller size
They are also called:
Terrestrial Planets
Answer:
- Comets are made of dust, rock and ice.
- They revolve around Sun in highly elliptical orbits.
- On approaching Sun, they form glowing head and tail.
- Tail always points away from Sun.
Example:
Halley’s Comet
First Law – Law of Ellipses
Planets revolve around Sun in elliptical orbits.
Sun lies at one focus.
Second Law – Law of Equal Areas
Line joining planet and Sun sweeps equal areas in equal intervals of time.
Third Law – Law of Harmonics
Square of orbital period is proportional to cube of semi-major axis.
Answer:
- Suitable distance from Sun
- Suitable temperature
- Presence of water
- Atmosphere
- Ozone layer
# Mercury
- Nearest planet to Sun
- Rocky planet
- Fastest revolution
# Venus
- Hottest planet
- Similar size to Earth
- Rotates opposite direction
# Earth
- Only known life-supporting planet
- Blue appearance due to water
- Revolution period:
# Mars
- Red planet
- Two small moons
# Jupiter
- Largest planet
- Gas giant
- Has Great Red Spot
Correction:
Jupiter has more than 90 known moons, not 65.
# Saturn
- Famous for rings
- Gas giant
# Uranus
- Rotates on its side
- Cold gas giant
# Neptune
- Windiest planet
- Has moon Triton
ISS = International Space Station
Benefits:
- Water purification technology
- Medical advancements
- Robotic surgery techniques
- Vaccine development
- Cancer research
Definition
Minimum horizontal velocity needed to keep satellite in orbit.
Important Points
- Depends on altitude
- Nearer satellites require greater speed
Formula
Where:
- (G) = gravitational constant
- (M) = mass of Earth
- (R) = radius of Earth
- (h) = orbital height
Geostationary Orbit
Satellite appears fixed relative to Earth.
Orbital period:
Answer:
Colour depends on temperature.
- Hot stars → blue/white
- Cooler stars → orange/red
Answer:
Satellite is launched with high horizontal velocity.
Earth’s gravity provides centripetal force needed for circular motion.
Answer:
They revolve around Earth in exactly 24 hours and remain above same location on Earth.
Answer:
Sun’s gravity is about 28 times Earth’s gravity.
Scientifically, this should refer to “weight equivalent,” not mass in kg.
Given:
Using orbital velocity formula:
Answer:
or
Given:
Using orbital period relation:
Answer:
Poster on Astronomers
Aim:
To learn contributions of astronomers.
Examples:
- Copernicus
- Galileo
- Kepler
- Newton
Observe Constellations
Observation:
Groups of stars form recognizable patterns.
Examples:
- Orion
- Ursa Major
Observe Planets
Observation:
Some planets visible to naked eye:
- Mercury
- Venus
- Mars
- Jupiter
- Saturn
Indian Satellites
Example List:
| Satellite | Purpose |
|---|---|
| Aryabhata | Scientific research |
| INSAT | Communication |
| IRS | Remote sensing |
| Chandrayaan | Moon mission |
| Mangalyaan | Mars mission |
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