PHYS-CHAP17-STARS Flashcards
What is a Celestial Body? Give Examples
Any natural body outside earth’s atmosphere is called a celestial bodies
Example
Stars, Planets, Moon, Asteroids, Moons etc. are Celestial Bodies
https://www.teachoo.com/10517/3036/Celestial-Bodies/category/Concepts/
What is Astronomy?
Study of Celestial objects and their phenomena is called as astronomy
What is solar system?
Sun and all celestial bodies around it form the solar system
It includes -
Sun + Planet + Satellites + Asteroids + Comets + Meteors
Note: It does not include Stars except the Sun
What are different phases of moon ?
Various shapes of moon seen during the month is called Phases of moon
The day on which the whole moon is visible is known as the full moon day.
After the full moon day, the size of bright part of moon reduces everyday.
On the 15th day, there is no moon. This is called no moon day.
After no moon day, only a small portion of the moon appears in the sky. This is known as the crescent moon.
And then, it increases everyday
After about 29 days, we see the full moon again
Why do we see different phases of moon?
- Moon does not produce its light
- But sun and other stars do produce light
- We see the moon because the sunlight falling on it gets reflected towards us.
- We therefore, see only that part of the moon, from which the light of the Sun is reflected towards us
What is the Significance of phases of the moon ?
Almost all festivals in India are celebrated according to the phases of the moon.
For example, Diwali is celebrated on the new moon day;
Budh Poornima and Guru Nanak’s birthday are celebrated on full moon day
Eidul-Fitr is observed on the day following the sighting of crescent moon.
Why do we see only one side of moon?
1.We only see one side of the moon because,
the moon rotates around the Earth at the exact same speed as it rotates around its own axis
- So, it takes equal time to rotate and revolve
- This is why we see only one side of moon
https: //www.teachoo.com/10518/3036/Moon/category/Concepts/
What is time period between 2 full moons?
It is little more than 29 days
In some calendars, this period is called month
What is in the Moon’s Surface ?
- When astronauts landed on the moon, they found that the moon’s surface is dusty and barren.
- There are many craters of different sizes.
- It also has a large number of steep and high mountains.
- First astronaut to land on moon was Neil Armstrong.
What are Stars?
Star is a celestial body
They are extremely hot and emit light of their own
Example
Sun is the nearest star to us
Alpha Centauri is second nearest star to us
Why are stars not visible during daytime?
Stars are present during day also
They are not visible due to bright sunlight
Why do stars appear from east to west?
Actually stars do not move
Because earth rotates from west to east on its axis ,it appears that stars appear to move from east to west
(Just like when we sit in moving train,it appears that all the nearby trees and buildings are moving backwards,but they are actually not moving)
Which star does not appear to move?Why?
Pole star does not appear to move
It is because it lies close to axis of rotation of earth
So even when earth rotates,it does not seem to change
Do stars in the sky move?
No they dont move in the sky
Since earth rotates from east to west direction, the stars appear to move from west to east direction.
This is like when we travel in train, it appears all places move behind us
What is light year?
Distance travelled by light in one year is called as light year.
Light travels 3 * 10^8 Km/s in one year or 300,000 kms per year
What is the light year distance in one year?
Speed of Light = 3 × 10 8 m/s
Time = 1 Year = 365 days = 365 × 24 hours = 31536000 seconds
Now,
1 Light Year = Speed × Time
= 3 × 10 8 × 31536000 m = = 94608000 × 10 8 m = 94608000 × 10 8 × 1/000 km
= 94608 × 10 8 km = 9.4608 × 10 4 × 10 8 km = 9.4608 × 10 12 km
How much time will it take for light to reach from sun to earth?
Distance of sun to earth = 150000000 km
Speed of Light = 300000 km/second
Time taken = 150000000/300000 seconds
= 500 seconds
Time taken in minutes = 500 second/60
= 8.33 minutes
So, it takes around 8 minutes for Sunlight to reach earth
What are Constellations?
Constellation is a group of stars forming a recognizable shape or pattern.
Which is the brightest star in solar system.How to identify it?
https://www.teachoo.com/10521/3036/Constellations/category/Concepts/
What are the planets in our solary system?
There are 8 planets.
Note: Pluto is not a planet. it is a dwarf planet.
https://www.teachoo.com/10522/3036/Planets-in-our-Solar-System/category/Concepts/
Name the inner planets of the solar system
Planets which are close to the sun are known as the inner planet
They are Mercury,Venus,Earth,Mars
Inner planets have very few moons
Name the outer planets of the solar system
Planets which are far away from sun are known as the outer planets
They are Jupiter,Saturn,Uranus,Neptune
Outer planets have large number of moons
How does Earth appears from Moon
Earth appears to be of blue-green color because of the reflection of water and land on its surface
What causes change of season on Earth
It is due to rotational axis of earth which is tilted
Part of earth which is nearer to sun has summers
Part of earth which is far from sun have winters
Example
In Northern Hemisphere(India,England) we have summers in May-june and winters in Dec-Jan
In Southern Hemisphere (Australia,New Zealand) there are winters in may-June and summers in Dec -Jan
https://www.teachoo.com/10522/3036/Planets-in-our-Solar-System/category/Concepts/
