Presentation on theme: "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."— Presentation transcript:
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
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
Heavy element synthesis
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.
Size vs Period
Gravity versus Thermodynamics
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 )