Special Stars Neutron Stars Black Holes

Massive Star Evolution 4 Massive stars burn hot and bright while on the main sequence, usually as a blue or whitish-blue star. 4 They burn through their hydrogen quickly, lasting only a billion years or so on the main sequence. 4 After expanding into supergiants, their cores collapse to produce supernovas and ultimately neutron stars or black holes.

Supernova 1987

Neutron Stars 4 Contain about 2 solar masses in a size of about 20 miles across. 4 Incredibly dense! (equal to cramming all people on Earth into a sugar cube) 4 Form from the collapse of a massive-star core following supergiant stage. 4 A person would weigh 21 trillion pounds on surface!

Black Holes 4 Form when the core of a super-massive star collapses after supergiant stage. 4 At its center is a singularity, an object of unimaginable density. Could be like taking the mass of our earth and compacting it onto a needle-head. 4 Gravity close to it pulls everything (including light) into it.

How do we “see” them? 4 Matter being pulled into them give off X- rays. 4 We can see the X-rays until it gets to the “event horizon”; once inside this radius light cannot escape. 4 It is believed that they are found at the center of most galaxies.

Evaporation 4 So will black holes “suck up” the universe? 4 Answer: No. They eventually evaporate by changing matter into energy. 4 They radiate energy into space when they reach a critical mass and disappear (according to unproven theory by Stephen Hawking).