Final Fate of a Massive Star

1. Pankaj S. Joshi Final Fate of a Massive Star

2. Science tries to Understandthe Nature & Structure of the Universe What are the Fundamental Laws Governing the Cosmos? The Quest begins with Observations And Experiments

7. The Universe The visible Universe is made of Stars and Galaxies Each Galaxy contains 400 to 500 Billion Stars Universe has Billions of such Galaxies Universe is Expanding NOW, WE FIND THAT THE UNIVERSE ACCELERATES!

8. Dark Energy and Exploding Stars The Observations on Accelerating Universe are intimately related to the Measurements on Exploding Stars, far away in Cosmos This indicates to a great mystery in Cosmology Today, which is the possible Presence of a Dark Energy in the Universe

9. One of the Most Important Key Issues in Modern Cosmology:What Happens when a Massive Star dies? Chandrasekhar's work—Star collapse and Stable Configuration Limit Continual Collapse for Massive Stars What is the Final End state of such a Continual Collapse?

13. Chinese Observations In 185 AD, Chinese astronomers observed Appearance of a bright star in our Milky Way galaxy. It took almost eight months to fade away from the sky. It sparkled like a star in the sky. Today we know it was a `Supernova'.

15. Supernova The core collapses in less than a second, Causing an explosion called Supernova. In which a shock wave blows off the outer layers of the star. The Supernova shines brighter than the entire galaxy for a short time.

17. We are made of Stars! After all the Hydrogen in the star was converted to Helium, for about a Million years other elements such as Carbon And others are cooked within the Star. The Supernova then throws them out in the Faraway Sky. Thus all the elements of which our Human Bodies are made were Cooked in faraway stars once upon a time!

18. Stellar Conception A star’s life begins in darkness, in an optically opaque molecular cloud Shielded by dust and gas from galactic starlight and cosmic rays, the cloud cools In the densest clumps of molecular gas, gravity overcomes internal pressure: clumps contract

19. A zoom-in to a massive star forming region Eagle Nebula (M16) Picture credit: T.A. Rector & B.A. Wolpa

20. Star and Planet Formation Summary Molecular Cloud Rotating Clump Forming Star + disk

22. Big Stars & Small StarsSmall stars like Sun live for Billions of years.But stars which are 10 or 20times the Sun live for only a fewcrores of years.That is because they burn much faster and finish their internal fuelvery quickly.

23. Recall the earlier Chandra comments in 1935!

26. Spacetime Singularities # General Relativity predicts that the gravitationally collapsing star must terminate into a spacetime singularity. # The densities, curvatures and all physical quantities must go to infinity closer to the singularity # Are such singularities of collapse visible to external observers in the Universe? THIS IS ONE OF THE MOST IMPORTANT ISSUES IN BLACK HOLE PHYSICS TODAY

27. This Information on Existenceof Singularities is rather general What we need is a more specific information on What happens When a Massive Star collapses. In particular, we need to know on the Visibility or otherwise of the Super-Ultra-dense regions, or the Singularities forming in Gravitational Collapse

28. Use GR/Homogeneous Dust cloud/Dynamical Collapse/Formation of Event Horizon/Spacetime Singularity and a Black Hole Region in the Spacetime/Collapse settles to a Final Schwarzschild Geometry Oppenheimer-Snyder Gravitational Collapse Scenario

30. The Past Status of Black Holes My Seminar at TIFR more than 20 years ago-- People asked: WHY BLACK HOLES? NOW BLACK HOLES EVERYWHERE! (Why your Talk has No Black Holes!!) There are very many unresolved issues also, associated with Existence and Physics Of Black Holes The Black Hole Conundrum

31. A & A DEVELOPMENTS Discovery of Quasars, Radio Galaxies, and Of several High Energy Phenomena in the Universe No known physics explains such High Energy Observations!! 1960s: Resurgence of Interest

32. Very Many Developments in the Physics & Astrophysics of Black Holes J Wheeler/R Penrose/S Hawking/K Thorne... Investigations in Classical & Quantum Aspects Of Black Holes Interesting Thermodynamic Analogies Astrophysical Applications Result

33. # Will a generic star go the Oppenheimer-Snyder-Datt way only, and make Black Hole only? Because, real stars are Inhomogeneous, have Internal pressure forces... # This is an Unanswered Question. Therefore the above Hypothesis, that Any Star Collapse will make a black hole only, hiding the Singularity And the ultra-dense regions behind an Event Horizon COSMIC CENSORSHIP HYPOTHESIS

41. STUDY GRAVITATIONAL COLLAPSE AS OPPENHEIMER AND SNYDER DID! Over past decade and a half, Numerous Collapse studies carried out... CONCLUSIONS: Black Holes and Naked Singularity Final States develop as The Collapse Outcome Way Out: Back to Basics

49. Small & Big Stars Some times the core survives the explosion. If the surviving core is between 1.5 to 3 Solar masses, it contracts to become a tiny Very dense neutron star. If the core is greater than 3 solar masses, The core contracts to become a Black Hole or a Fire Ball