Transcript Black Holes
Black Holes This one’s green. I like green. What happens after a SN? • Material remaining after a supernova is 3 times more massive than the sun or more • Pressure is strong enough to collapse the star beyond the neutron-degeneracy pressure. • Star remnant collapses and vanishes. Characteristics of a black hole • MATTER IN A BLACK HOLE LOSES ALMOST ALL OF ITS ORIGINAL CHARACTERISTICS! • Retains only: – Mass (therefore the gravity) – Its angular momentum *** All other characteristics no longer exist! • concepts like protons, electrons, neutrons, molecules, compounds etc. no longer apply. ??? I have a headache. • Escape Speed- speed needed for an object to escape the gravity of another. – Bigger mass= bigger grav, then bigger ES – Smaller radius= bigger grav, then bigger ES • The escape speed for a black hole is greater than the speed of light. • Nothing can exceed the speed of light (except Bause when he runs towards the lunch line) SO nothing can escape a BH Singularity • General relativity (Einstein) predicts that in creating a black hole, matter compresses to infinite density. • ALL known laws of physics are invalid. • Recall Relativity explains the behavior of the really massive, quantum mechanics explains the behavior of the really small (subatomic stuff). A black hole is both REALLY massive and REALLY small. Schwarzschild radius • The radius that matter (any matter, does it matter?) must be compressed for it to have an escape speed equal to the speed of light. • All objects have a SR – Earth = 1 cm or a grape – Jupiter = 3 cm or 3 grapes (I’m not creative) – Sun = 3 km Event Horizon • The location around a black hole where the escape speed EQUALS the speed of light. • Everything in the EH is lost forever. No information can be gathered from within. • Outside of the EH, everything appears to “slow”… called gravitational redshift Gravitational Redshift • Speed of light is CONSTANT through constant medium. • In order for light to escape gravity it must work (use energy). Greater the grav, more energy. • SO, light will lose energy and shift towards red portion of electromagnetic spectrum (longer wavelength) Gravitational Lens • Gravity can bend light rays. • This can allow us to see objects normally too far for us to see. • Bause diagram. All galaxies… ranging from 3 bill. ly to 9 bill ly. Sphagettification? Infalling Matter • Matter closest to the BH will be pulled greater, stretching the matter. • Eventually pulled apart, atom by atom. Does a black hole last forever? • Nope. • They can evaporate through Hawking Radiation (more in your lab). • Process takes a LONG time. A 5 solar mass black hole would take 1062 years to evaporate. So, black holes that have formed, still exist today. Supermassive Black Holes • All elliptical and spiral galaxies seem to have one in the center. Irregular galaxies (aka dwarf galaxies) do not. • A black hole with the mass of millions to billions of Suns!