Final Fate of a Massive Star

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

2. I. INTRODUCTORY II. A STABILITY ANALYSIS: Introducing Small Pressures in Dust Collapse III. CURRENT PERSPECTIVE AND CONCLUSIONS The talk is divided in the following main parts:

5. One of the Most Important Key Issues in Relativistic Astrophysics and CosmologyWhat 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?

6. The Observations on Accelerating Universe are intimately related to the Measurements on Exploding Stars, far away in Cosmos. This is linked to a great mystery in Cosmology Today, which is the possible Presence of a Dark Energy in the Universe. In Supernovae, the core collapses in less than a Second, causing a Massive Explosion. A shock wave then blows off the outer layers of the star. The Supernova shines brighter than the Entire galaxy for a short time... Dark Energy and Exploding Stars

11. Recall the earlier Chandra comments in 1935!

14. Spacetime Singularities # General Relativity predicts that under reasonable physical conditions the gravitationally collapsing massive 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

15. Use General Relativity/Homogeneous Density Spherical Dust cloud with No Rotation or Pressures Dynamical Collapse/Formation of Trapped Surfaces and Event Horizon/Collapse to a Spacetime Singularity/Formation of a Black Hole Region in the Spacetime Collapse settles eventually to a Final Schwarzschild Geometry Oppenheimer-Snyder-Datt Gravitational Collapse Scenario

17. The Past Status of Black Holes My Seminar on Black Holes at TIFR more than 20 years ago-- Astronomers asked: WHY BLACK HOLES, WHY YOU TALK ON SUCH EXOTIC THINGS? 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

18. 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

19. 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

24. COSMIC CENSORSHIP HYPOTHESIS # Will a generic star go the Oppenheimer-Snyder-Datt way only, and make a Black Hole only? Because, real stars are Inhomogeneous, have Internal pressure forces... # This is an Unanswered Q. Therefore the Hypothesis by Penrose: Any Star Collapse will make a black hole only, hiding the Singularity, the ultra-dense regions, behind an Event Horizon THIS HAS BEEN ONE OF THE MOST FUNDAMENTAL QUESTION IN GRAVITATION THEORY TODAY

25. What we need to know specifically is: What happens When a Massive Star collapses under its own gravity. In particular, we need to know on the Visibility or otherwise of the Super-Ultra-dense regions, or the Singularity that forms in such a Gravitational Collapse TOWARDS THIS PURPOSE, EXPLICIT MODELS NEED TO BE WORKED OUT, IN THE ABSENCE OF ANY GENERAL PROOF The Information given by Singularity Theorems on the Existence Aspect is rather general

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

33. To Understand the Rich Structure allowed by the Einstein Equations in Dynamical Collapse, We studied recently Explicitly the Role of Pressures in Collapse Evolutions, by Introducing Small Pressures in otherwise Pressure-free OSD Model (PSJ & D Malafarina, Physical Review, in Press) Such Studies are Extremely Essential in view of our Failure so far towards any Proof, or even making any possible Mathematical Formulation of the Cosmic Censorship Hypothesis Basically, we need to understand much more Carefully, what all is possible in Gravitational Collapse

34. What happens to the Collapse outcome when arbitrarily small pressure perturbations are introduced within the OSD Collapse Scenario? We obtain here the Explicit Classes of Pressure Perturbations such that introducing a smallest pressure changes the final outcome of collapse from Black Hole Final State to a Naked Singularity What we see is a Very Rich Structure of the Initial Data Space, in terms of the Collapse Outcomes Small Pressure Perturbations in the OSD Dynamical Collapse System

35. Gravitational Collapse in a Comoving Coordinate System

36. Introducing a scaling function R=rv, and F(r,v) = r^3 M(r,v), it is possible to integrate the Einstein equations to get the Equation of Motion of the Collapsing Fluid, the key point is to understand the structure of trapped surfaces. While doing so, one must ensure that the Collapse develops from a Regular initial Data. The Trapped Surfaces and Spacetime Singularity Develop then as the collapse evolves, and the main task then is to examine the Nature of the Singularity, namely whether it is Covered within Horizon, or Visible to External Observers.

37. OSD Model is then given by, The function t(v,r) gives time for a shell at r to reach a coordinate value v, the Spacetime singularity being at v=0

38. For the OSD model, {g_00} is necessarily Unity. We now allow it to be non-zero, this amounts to introducing small non-zero tangential pressures (with M=M_0 only).

39. The Singularity Curve and Apparent Horizon are given by

49. Examples: Dust Collapse, Radiation Collapse... Why Do Naked Singularities Develop in Gravitational Collapse? How Trapped Surfaces are Naturally Delayed due to Inhomogeneities Physically Realistic Collapse implies Naked Singularity always?