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Formation of Stars and Galaxies. Introduction 1.Timeline and Big Bang.

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Presentation on theme: "Formation of Stars and Galaxies. Introduction 1.Timeline and Big Bang."— Presentation transcript:

1 Formation of Stars and Galaxies

2 Introduction 1.Timeline and Big Bang

3 The Instruments 1. Optical Telescopes a)Use different regions of Electromagnetic Spectrum i.Visible EM region ii.Infrared EM region iii.Ultraviolet EM region b)Types i.Refracting ii.Reflecting iii.Catadioptric 2.Radio Telescopes 3.X-Ray and Gamma-Ray Telescopes

4 The Objects 1.Stars 2.Nabula 3.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 Hubbles Tuning Fork ….. moremore NGC4414 M87 NGC1427A

5 i.Elliptical Galaxies are numbered E0 - E7. As we go to larger numbers they are flattened more and more ii.Spiral Galaxies are categorized into Sa,Sb and Sc on the basis of spiral arms and central bulge iii.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 iv.Irregular Galaxies have no particular shape

6 4.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 ~ 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 solar masses and large amounts of dark mattera 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 10 5 solar masses. A cluster is member of supercluster

7 5.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 10 5 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 ….. moremore

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 8.Voids A void billion light years across was found in 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 1.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<

11 Galaxies Formation 1.Models and Computer Simulations 2.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 6.Top-Down Formation 7.Bottom-Up Formation 8.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. 10.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. 1.Accretion of gases and shrinkage under gravity at 10 kelvin or less forms a protostar. 2.Shrinkage continues and temperature rises. 3.At few million kelvin therminuclear reactions of hydrogen start. Protostars less than 0.08 solar masses (0.08M) can never start thermonuclear process. 4.Time of shrinkage and burning of hydrogen depends on mass of protostar. 5.After hydrostatic and thermal equibrium star becomes a stable star and occupies the main sequence of H-R diagram. ……. DiagramDiagram

15 Star Formation H-R Diagram

16 1.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 2.At 100 million kelvin at the core helium burning starts producing carbon and oxygen. 3.At 600 million kelvin and mass equl to 4 M carbon burning begins producing neon, oxygen and magnesium 4.At 1.2 billion kelvin neon burning begins 5.At 1.5 billion oxygen starts burning. Pricipal prouct is sulpher, it also produces silicon, phosphorus and magnesium 6.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. 7.When density reaches more than 4x10 17 kg/m 3 a neutron star is born. If mass >3.0M it will become a black hole. 8.For 25M carbon burns for 600 years, neon for 1 year, oxygen for 6 months and silicon in 1 day. Nucleosynthesis of Stars

17 END

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