• What happens to space-time near a black hole?

• Why are black holes black?• What observational evidence

do we have for black holes?

Black Hole Questions

Few SolarMasses

>106

Solar Masses

Core-collapse supernovae: for M > 3Msolar neutron degeneracy pressure cannot support a star against gravity

Supermassive black holes that form in the centers of galaxies as they form

Black Holes: Formation

Newton (1687)

F = GM1M2/R2

Einstein

Special Relativity (1905) -Relates space and time in a 4-dimensional spacetime (nothing can move faster than the speed of light)

General Relativity (1915)-Gravity is the curvature of space by mass⇒Even light is bent by gravity!

What if M1=0?

A New Theory of Gravity

Spacetime around the Sun Spacetime around a 1Msolarwhite dwarf

Fig.

S3-

15A

Fig.

S3-

15B

Spacetimearound the Sun compressed to a black hole

The Curvature of Space

What would happen to the Earth’s orbit if the Sun were replaced with a 1 Msolar black hole?

A)The Earth would spiral into the black hole.B)NothingC)The Earth would escape from the solar

system.

Concept Question

What would happen to the Earth’s orbit if the Sun were replaced with a 1 Msolar black hole?

A)The Earth would spiral into the black hole.B)NothingC)The Earth would escape from the solar

system.

Concept Question

Viewgraph

The Event Horizon

Are black holes sucking everything into the Universe into them?—No talking to neighbors on this one.

A)YesB)No

Concept Question

Are black holes sucking everything into the Universe into them?—No talking to neighbors on this one.

A)YesB)No!—This is a popular

misconception

Concept Question

Fig. 18.12

Fig. 18.13

Time slows downThere are strong

gravitational gradients

Strange Things that Happen Near the Event Horizon

Cygnus X-1

Fig.

18.

14A

Fig.

18.

03

•Discovered in the 1970s by UHURU•2 kpc distant•Companion 8.5 ≤ M ≤ 20 Msolar, Black hole 3.3 ≤ M ≤ 5.5 Msolar•Variable X-ray emission (radius ≤ 300 km)

Observational Evidence for Solar-Mass-Scale Black Holes