White Dwarf Stage Stars with masses less than 8 times the sun's cannot fuse carbon and oxygen into heavier elements. These stars collapse into white dwarfs. At the final stage of the collapse, the outer layer's of the star are blown off to form a planetary nebula

White dwarf stars have no internal source of energy; the light they emit comes from stored heat. Because they are so small, the cooling process is very gradual. A white dwarf can exist for about 50 trillion years before becoming to cool to emit light. White dwarfs don't collapse further because of a quantum effect called electron degeneracy pressure. This process cannot support a structure whose mass exceeds 1.44 times the sun's mass.

Descent to White Dwarf

Cooling Embers

Mass-Radius for Degenerate Stars

Mass-Radius for White Dwarf

Mass-Radius for White Dwarfs

MS Mass – W Dwarf Radius

Pre SN core

Pre SN Core to scale

Multiple Shell Burning

Timescales to Supernova

Iron catastrophe

Heavy element synthesis

Cosmic Abundance

Neutron stars If the mass of a supernova remnant is less than 3 solar masses, a neutron star is formed. This object is a neutron ball between 10 and 20 miles in diameter! The structure doesn't collapse further because of neutron degeneracy pressure.

Pulsars Most neutron stars cannot be detected optically. Most are detected because they emit radio waves in short bursts whose period matches their rotation rate. These objects are called pulsars.

Pulsar

Size vs Period

Gravity versus Thermodynamics

Mass-Radius plot

Black Holes Stars with masses greater than 3 solar masses collapse into black holes. The gravity of a black hole is so strong that its escape velocity exceeds the velocity of light. The boundary of a black hole is called the event horizon.

Black Hole Collapse

Space-Time Warp At the Scwarzchild Radius Space-time is warped to such an extent that space and time reverse roles The spatial direction pointing to the centre takes the role of time Once across the Horizon, continuing to the singularity at the centre is as inevitable as going from the past into the future !

Falling in By your watch, you cross the event horizon at 12:00 The light coming from you between 11:58 and 11:59 is so time dilated that someone watching from a great distance sees the light spread out over a hundred years Similarly, you see a hundred years’ worth of light coming from the outside world in that minute. The light coming from you between 11:59 and 12:00 is so time dilated that someone watching from a great distance sees the light spread out over an infinite time ! You see an infinity’s worth of light in that last minute, the whole history of the universe ( perhaps more )

Event Horizon is inside ordinary objects

Black hole Contained within event horizon

Black Hole Observation