Recent advances in the study of black holes include: 1. The first image of a black hole was captured in 2019 using the Event Horizon Telescope, showing the shadow of the supermassive black hole at the center of the Messier 87 galaxy. 2. Gravitational waves detected in 2015 by the LIGO observatory provided direct evidence of black holes from the merger of two stellar-mass black holes. 3. Observations of stars orbiting Sagittarius A* provided evidence of a supermassive black hole at the center of the Milky Way galaxy. 4. X-ray binaries, where matter falls from a donor star onto a compact object like a neutron star or black hole

1. Recent advances in study of
BLACK HOLEPresented By:
Banuprakash M
ll year M.Sc Physics
Alva’s Centre for PG Studies,
Moodabidri

2. 1. History:
Pre-General theory of Relativity:
The idea of a body so massive that even light could not escape was briefly
proposed by astronomical pioneer John Michell in a letter published in November
1784.
 same density as the Sun.
 star's diameter exceeds the Sun's by a factor of 500.
 the surface escape velocity exceeds the usual speed of
light.
 non radiating bodies.
 They are detectable through their gravitational effect on
nearby visible bodies.

3. Post-General theory of Relativity(1915):
 Schwarzschild, Johannes Droste, a student of Hendrik Lorentz,
independently gave the same solution for the point mass in
Einstein field equation.
 This solution indicates Schwarzschild radius, where it became
singular, means some of the terms in the Einstein equations
became infinite.
 Subrahmanyan Chandrasekhar(1931) calculated, using special
relativity a non-rotating body of electron-degenerate matter
above a certain limiting mass has no stable solutions.
that is presently called Chandrasekhar limit at 1.4 M☉.
 In 1958, David Finkelstein identified the Schwarzschild surface as
an event horizon.
 In 1963, Roy Kerr found the exact solution for a rotating blackhole.
 Ezra Newman found the ax symmetric solution for a black hole
that is both rotating and electrically charged.
Stephan Hawking, in 1974, showed that quantum field theory
implies that black holes should radiate like a black body now it is
called Hawking radiation.

4. 2. Definition:
A black hole is a region of space time exhibiting gravitational acceleration so
strong that nothing, no particles or even electromagnetic radiation such as
light can escape from it.

5. 3. Formation and Evolution of Black hole:
Formation:
A. Gravitational collapse:
Gravitational collapse occurs when star’s internal pressure is
insufficient to resist it’s own gravity.
Reasons:
Star has little fuel left to maintain its temperature through the stellar nuclear
synthesis or a star would receives extra matter in a way that does not raise its core
temperature.
The condensation of matter into an exotic dense state.
The gravitational collapse of heavy stars is assumed to
Be responsible for the formation of stellar mass black
Hole.
A star with a mass greater than 20 times the mass of
our Sun may produce a black hole at the end of its life.

7. B. Primordial Black hole:
Primordial black holes are a hypothetical type of Black holes that formed soon
after Big bang.
In early universe shortly after Big bang densities are much high , this creates
possible formation of Black hole.
their masses can be far below stellar mass. Hawking calculated that primordial black
holes could weigh as little as 10−8 kg to hundreds of thousands of solar masses.

8. C. High Energy Collision:
By high energy collision that should achieve sufficient density.
Einstein's theory of general relativity, actually predicts that a black hole can be made
by particle collision.
By computer simulation, If the two particles collide with a total energy of about one-
third of the Planck energy*
No such events are observed directly or indirectly
* Choptuik and Pretorius Physical Review Letters.

9. 4. Structure and properties
Black Hole:
1. Quiet Region: negligible gravitational
Influence:
2. Ergo sphere:
3. Event horizon:
4. Gravitation space time distortion:
5. Singularity:
6. Photon sphere:

10. 5. Types of Black hole:
Black holes are commonly classified according to their mass and it does not depend
on angular momentum. Where Schwartz child radius depends on mass.
CLASS APPRX MASS APPRX RADIUS
Super massive black hole(SMBH) 105–1010 MSun 0.001–400 AU
Intermediate-mass black
hole(IMBH)
103 MSun 103 km ≈ REarth
Stellar black hole 10 MSun 30 km
Micro black hole up to MMoon up to 0.1 mm

11. 6. Observation evidence of Black hole:
6.1 First image of Black hole:
The image was took by Indirect Observations, Using Event Horizon telescope(EHT), in
April 2017 data is collected, after two years of processing in April 2019 first image of the
Super massive Black hole is released. The super massive black hole at the core of
supergiant elliptical galaxy Messier 87, with a mass ~7 billion times the Sun's.
s:Event Horizon Telescope, The (2019). "First M87 Event Horizon Telescope
Results. I. The Shadow of the Supermassive Black Hole".
The Astrophysical Journal. 87 (1): L1.

12. 6.2 Detection of Gravitational waves from merging Black hole:
On 14 September 2015 the LIGO gravitational observatory made first ever successful
direct observation of gravitational waves which are produced by the merger of two
Black holes.

13. 6.3 Proper motion of stars orbiting Sagittarius A*:
Sagittarius A* is a bright and very compact astronomical radio source at the center
of the Milky Way, Since 1995, astronomers have tracked the motions of 90 stars
orbiting an invisible object coincident with the radio source Sagittarius A*. It is
around 4.3 million M☉.
Ghez, A. M.; Klein, B. L.; Morris, M.; et al. (1998). "High Proper‐Motion Stars in the Vicinity of
Sagittarius A*: Evidence for a Supermassive Black Hole at the Center of Our Galaxy". The
Astrophysical Journal. 509 (2): 678–686.

14. 6.4 X-ray Binaries:
X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are
produced by matter falling from one component, called the donor, to the other
component, called the accretor, which is very compact: a neutron star or black hole.
Celotti, A.; Miller, J. C.; Sciama, D. W. (1999). "Astrophysical evidence
for the existence of black holes" (PDF). Classical and Quantum

15. References:
1. Introduction to Astrophysics by VidyanathBasu.
2. https://science.nasa.gov/astrophysics/focus-areas/black-holes
3. https://www.ligo.caltech.edu/page/what-is-ligo
4. https://space.mit.edu/~nss/binaries.html
5. Swayam course on Stars and stellar system conducted by IUCAA.