Universe Flashcards
Number of natural satellites in our solar system
59
Planets that don’t have any natural satellite
Mercury
Venus
Planet having maximum satellites and number of satellites it has
Saturn
Has 21 satellites
Ways in which stars can occur
Single stars
Binary stars
Clusters
Type of galaxies
Spiral
Elliptical
Irregular
Mass of Milky Way galaxy
M = (v^2 x r) / G
= 3 x 10^41 kg
=150 billion solar masses
What are asteroids
It is believed that asteroids are pieces of planets possibly due to gravitational effect of Jupiter
Comets?
Are small rock like material surrounded by large masses like water, ammonia and methane revolving in highly elliptical orbits around the sun
Meteors and meteorites?
Objects that get completely burned and blazing through the atmosphere are called meteors
While objects that aren’t completely burned are called meteorites
Hottest star
Blue star
Coolest star
Red Star
Observations in favour of Big Bang theory
Expanding universe
Red shift
Pulsating theory
States that the boundary of universe moves in and out with a time period of 8 x 10^9 years
Steady state theory
States that total number of galaxies present in the universe has attained a steady value.
Thus if one galaxy is lost another is lost due to annihilationa new ones formed
This theory is based on conservation of energy and mass
Hubble’s law
States that speed of recession(v) is related to distance(r) of Galaxy by the relation
v=Hr
H-Hubble’s constant = 10^17 kms-1/million light years
Formation of stars
Dust particles, Hydrogen and helium gas molecules in interstellar space combine together at -173 C
to form a cloud.
Try then start to contract and as a result of compression heating of cloud takes place.
At about 10^7 K fusion of H atoms is initiated with release of energy which keeps the stars shining for millions of years.
Death of star
After H in the core is exhausted the core starts contracting which increases the temperature
As a result the outer layer starts contracting which brings about a cooling effect
This process continues till the outer layer’s temperature drops to a point where the star appears red and the star is then called a Red Giant
This is followed by a violent explosion called nova/supernova in the star which throws the outer layers into interstellar space.
The left core may then convert into any one of the following before ultimately dying
1] white dwarf
2] Neutron star
3]Black Hole
White dwarf?
Was discovered by S. Chandrasekhar
The core which is made of protons and electrons dies as white dwarf of star’s original mass was 1.4 solar masses. This called Chandrasekhar limit.
Stars colour changes from white to yellow to red and finally black.
It then becomes invisible.
Neutron star
The core made up of neutrons finishes up as neutron star if it’s original mass is between 1.5 to 5 solar masses
These stars produce very high magnetic fields
What’s a Pulsar
A spinning neutron star emitting electromagnetic waves is called Pulsar
Black Hole
If the original mass of star is greater than 5 solar masses it dies as a black hole
Why does black hole have large gravitational pull?
Because mass of black hole is greater than that of sun but it has a small size and hence large gravitational pull
Composition of Milky Way
It is composed of a few hundred billion stars i.e. 150 billion stars
When and by whom was the Milky Way discovered
In 18th century by William Herschel
