Announcements Next time: finish reading The Five Ages. Exam 1 is scheduled for next Wednesday. Will cover Five Ages of the Universe only.

Colored Card Question The Stelliferous Era begins in which cosmological decade? a)The 14 th b)The 25 th c)The 6 th d)The 10 th

Another Colored Card Question During the Degenerate Era, most of the unburned hydrogen can be found a)in cool white dwarfs b)as cool gas between the galaxies c)in giant molecular clouds in the galaxies d)in brown dwarfs

One More Colored Card Question The Black Hole Era begins in which cosmological decade? a)The 40 th b)The 10 th c)The 75 th d)The 25 th

The Stelliferous Era The first generation stars may have been mostly dark matter: Dark Stars These stars may have had several thousand solar masses 6<  <14

CMB shows seeds of first galaxies The variation in temperature is only ~ one part in That’s enough to give rise to structure.

First galaxies were small irregular galaxies which slowly became spirals

Which came first: the black hole at the center of the galaxy or the galaxy?

Stellar formation today takes place in giant clouds of gas & dust

The gestation period depends on the mass

The fate of a star depends almost entirely on its mass

Death by planetary nebula formation

Death by supernova

Death by Hypernova

The current population of stars

Eventually only low mass stars are left The smallest red dwarf stars may live for tens of trillions of years but eventually even they die. At the end of the stelliferous era only supermassive black holes and stellar corpses are left.

The Degenerate Era White Dwarfs and planets Black Holes Brown Dwarfs

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 They are not entirely degenerate. These, planets and any surviving asteroids or comets are the sole reservoirs of ordinary matter left during the degenerate era.

There are currently many more stars than brown dwarfs

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

White Dwarfs are the size of planets with the mass of stars

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 Single atom Energy Level Diagram Degenerate Matter 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

Neutron Stars aren’t entirely neutrons

Eventually the protons decay There are other possible decay mechanisms. The current best estimate for the half-life of the proton is ~10 34 years. Once all the protons decay away, there is no ordinary matter, degenerate or non-degenerate, left in the universe

At the end of the Degenerate Era only black holes are left