Stellar Corpses and Other Space Oddities Black Holes, Neutron Stars, Nova and other creatures in the stellar zoo

End of a Massive Star Core contracts and becomes neutronized by reverse Beta decay Collapse either is stopped by degeneracy Or, for very massive core (3M) collapse isn’t halted

Neutron Stars Core Mass 1.4-3M Very dense ( 1 teaspoon= 1billion tons) Small in size (10-30km) STRONG magnetic field Likely spinning rapidly Postulated in 1930’s Not widely accepted until 1968

Neutron Stars and Pulsars Pulsars discovered in 1968 Beaming “pulses” of EM waves at regular intervals LGM at first! Lighthouse Model All Neutron Stars may be Pulsars

Lighthouse Model Rotation Axis Beamed Radiation Magnetic Field Neutron Star

Pulsars Millisecond Pulsars Pulsars are slowing Can be in Binary systems Maybe a source of X-ray Binaries Neutron Star is accreting material from companion

Black Holes If collapse is not halted Mass collapses to a singularity Singularity is a point “Punches a hole” in space-time Curvature of spacetime Gravity is extremely strong

Black Holes Escape Velocity greater than c Like standing on a rubber sheet holding an anvil (2D analogy) Black holes are actually 3D objects Think Flatland! Event horizon-boundary between BH and observable universe Schwarzschild Radius

Black Holes Strong Gravity Tidal Forces Relativity takes over (time slows) No way to get knowledge from interior Much indirect evidence for Black Holes Also form X-ray binaries Use formula to find mass of unseen companion

Black Holes Have No Hair Matter in a black hole becomes simple in form Loses all identifying features except Electric Charge Mass Angular Momentum No protons, electrons, neutron etc

Two Types of Black Holes Schwarzschild Black Hole – “classic” non-rotation Kerr Black Hole- rotating, can escape from (maybe) Black Holes may be evaporating from Hawking Radiation

Black Hole Binary Systems Roche Lobe Overflow Wind X-ray Jets Black Hole Companion Star Accretion Disk

Nova A WD in binary system Accretes matter from companion Gets stellar “indigestion” Flares up and brightens Calms back down Process begins again Doesn’t disrupt star

Type I Supernova Same setup as Nova Accretion occurs much faster Star can’t “burp” off material Exceeds Chandre mass Star begins a rapid collapse w/core bounce Supernova that completely destroys WD

Supernova Comparison Type I much more luminous that Type II Both form Supernova Remnants (SNR) Type I have less material in SNR Material is moving much faster in Type I Type I have no Hydrogen in spectra Type II do

Hypernova and Gamma Ray Bursts New idea Very powerful supernovae Could be generating BH instead of NS Collapse of BH leads to Gamma Ray Burst Gamma Ray bursts are random No one knows what they are!

Summary Massive stars can leave behind unusual corpses Supernova come in different types