1. Formation of
Stars and Galaxies

2. Introduction
1. Timeline and Big Bang

3. The Instruments a) Use different regions of Electromagnetic Spectrum
1. Optical Telescopes
a) Use different regions of Electromagnetic Spectrum
Visible EM region
Infrared EM region
Ultraviolet EM region
Types
i. Refracting
Reflecting
Catadioptric
Radio Telescopes
X-Ray and Gamma-Ray Telescopes

4. The Objects Stars Nabula Galaxies ( More than 100 billion )
i. Have 10 million to one trillion stars
ii. Most galaxies are 1,000 to 100,000 parsecs in diameter and are usually separated by distances of the order of millions of parsecs (mpc).
NGC1300
Types of Galaxy
i. Elliptic
ii. Spiral
iii. Barred-Spiral
iv. Irregular
Hubble’s Tuning Fork ….. more
NGC4414
M87
NGC1427A

5. Elliptical Galaxies are numbered E0 - E7
Elliptical Galaxies are numbered E0 - E7. As we go to larger numbers they are flattened more and more
Spiral Galaxies are categorized into Sa,Sb and Sc on the basis of spiral arms and central bulge
Barred Spiral Galaxies have a bar connecting spiral arms and are categorized into SBa,SBb and SBc on the basis of spiral arms and central bulge
Irregular Galaxies have no particular shape

6. Groups , Clusters and Superclusters
i. Group
A group of galaxies contain about < 50 galaxies, a diameter of 1 to 2 megaparsecs, masses contained in groups is typically ~ 1013 solar masses and the model applied is CDM.
ii. Cluster
A cluster of galaxies contain 50 to 1000 galaxies, hot X-ray emitting gas, clusters typically have masses from to 1015 solar masses and large amounts of dark matter a diameter from 2 to 10 Mpc . A group is a member of cluster
iii. Supercluster
A superstructure can have extents of order 100 Mpc, have masses above 105 solar masses. A cluster is member of supercluster

7. Filaments
of galaxies are 50 to 80 mpc in length
6. Black Holes and Supermassive Black Holes
i. If a collapsing star of over 3 solar masses does not eject matter, it becomes a black hole.
ii. a mass of an order of magnitude between 105 and of solar masses. Most, if not all galaxies, including the Milky Way, contain supermassive black holes at their galactic centers.
7. Dark Matter and Dark Energy ….. more

8. Dark Matter and Dark Energy
Distribution
Dark Matter reflects no light and combined with Dark Energy it is more than 90% of the mass of the universe. Theories of evolution of universe are based on Hot, Warm and Cold characteristics of Dark matter and energy.

9. Voids
A void billion light years across was found in 2007
9. Walls
i. Great Wall (cfA2) of galaxies, a very large structure discovered in1989 is 500 million l years long, 200 million l years wide and 15 million l years thick.
ii. Sloan Great Wall of galaxies , the largest structure discovered in 2003 is 1.37 billion light years but is not a structure in the strict sense

10. Big Bang and Models of Cosmology
Lambda - CDM ( Cold Dark Matter )
It explains cosmic microwave background observations, as well as large scale structure observations and supernova observations of the accelerating expansion of the universe. Cold Dark Matter is explained as being cold its velocity is non-relativistic (v<<c) ,can not cool by radiating photons and collisionless (i.e., the dark matter particles interact with each other and other particles only through gravity).
2. WDM ( Warm Dark Matter )
Recently WDM predicted the Black Hole formation at the centrer at the center of galaxy.
3. HDM (Hot Dark Matter)
It is represented primarily by neutrinos, does not apparently account for the pattern of galaxies observed in the Universe.
Discovery of dim dwarf galaxies filling void negates HDM.
The two models CDM and WDM are still competing with each other and computer simulations don’t discard them.

11. Galaxies Formation Models and Computer Simulations
Primordial Fluctuations
Large clumps of gases and protogalaxies are formed
3. Central Quiescent theory
Inside Dark Matter halos galaxies are formed by slow accretion. Massive galaxies should be bright.
4. Collisional Starburst Scenario
Galaxies are formed quickly by collisions between small clumps of matter , produces could trigger a huge burst of star formation.
5. Supermassive Black Holes at the center
small "seed" black holes, which formed in the very early universe, served as gravitational "roots" for the clouds of gas around them

13. Top-Down Formation
Bottom-Up Formation
Formation of Spiral Galaxies
Lambda-CDM Model supports it. Slow star formation
9. Formation of Elliptical Galaxies
Formed by merger of Galaxies and quick star formation. Have supermassive black holes at the centers.
Formation of Barred-Spiral Galaxies
possible cause of bar creation is tidal disruptions between galaxies. The bar structure decays over time

14. Star Formation
1. Accretion of gases and shrinkage under gravity at 10 kelvin or less forms a protostar.
Shrinkage continues and temperature rises.
At few million kelvin therminuclear reactions of hydrogen start. Protostars less than 0.08 solar masses (0.08M) can never start thermonuclear process.
Time of shrinkage and burning of hydrogen depends on mass of protostar.
After hydrostatic and thermal equibrium star becomes a stable star and occupies the main sequence of H-R diagram. ……. Diagram 1.

15. Star Formation
H-R Diagram

16. Nucleosynthesis of Stars
After consuming hydrogen if the star is less than Chandrashekhar limit of 1.4Mass of the sun, it will become a white dwarf having volume about earth
At 100 million kelvin at the core helium burning starts producing carbon and oxygen.
At 600 million kelvin and mass equl to 4 M carbon burning begins producing neon, oxygen and magnesium
At 1.2 billion kelvin neon burning begins
At 1.5 billion oxygen starts burning. Pricipal prouct is sulpher , it also produces silicon, phosphorus and magnesium
At about 2.7 billion kelvin silicon burning starts it produces iron and further burning stops. Any star with more than 10M can develop iron core.
When density reaches more than 4x1017 kg/m3 a neutron star is born. If mass >3.0M it will become a black hole.
For 25M carbon burns for 600 years, neon for 1 year, oxygen for 6 months and silicon in 1 day.

17. END