Announcements • Lecture PowerPoint's are posted on class website as PDF files and as PowerPoint slides • Next time: if we don’t finish The Five Ages of the Universe today, we will finish it next time so start reading the Foundations of Modern Cosmology textbook. • Exam 1 is scheduled for two weeks from today. Will cover Five Ages of the Universe plus first few chapters of Foundations of Modern Cosmology.
The degenerates all start off as stars White dwarf’s, neutron stars and stellar mass black holes all start as stars. There are larger black holes, galactic black holes, that didn’t start as stars, though.
Brown Dwarf Stars are failed stars These are not degenerate. These, planets and any surviving asteroids or comets are the sole reservoirs of ordinary matter left during the degenerate era.
Brown Dwarfs are comparable in size to Jupiter The interiors of brown dwarf’s become highly compressed so they don’t get much larger than Jupiter even with 40 or 50 times the mass. They can become degenerate at their core
Some White Dwarfs “grow” by accreting mass from companions During the Degenerate Era this doesn’t happen any more but it is not uncommon during the Stelliferous Era
In degenerate matter only the highest energy levels are available Degenerate Matter Energy Level Diagram Single atom Energy Level Diagram
Degenerate objects get smaller when mass is added This applies to white dwarf’s and neutron stars but not black holes. Black holes are beyond degenerate
During the Degenerate Era most of the energy may come from dark matter annihilation
Eventually the protons decay There are other possible decay mechanisms. The current best estimate for the half-life of the proton is ~1034years. Once all the protons decay away, there is no ordinary matter, degenerate or non-degenerate, left in the universe
The Black Hole Era To understand black holes, we need to explore Einstein’s General Theory of Relativity
Tidal forces stretch and squeeze anything falling into a black hole The process is called Spaghettification. Watch spaghettification video
Most black holes now are accreting mass and have jets Because the star that formed the black hole was rotating and the mass falling in spirals inward, the black hole is rotating: it is a Kerr black hole
The Binary Pulsar When they finally collide, they will form a black hole. Watch Binary Pulsar and Neutron Star Merger videos On thumb drive
At the end of the Black Hole Era only electrons, positrons, extremely long wavelength photons and a few exotic elementary particles remain. The Dark Era is truly dark
The Dark Era e+ e- e+ e-
Phase Transitions Ice pockets forming in a salt water pool
The probability of tunneling depends on the wave properties of the universe