BLACK HOLES & NEUTRON STARS

BLACK HOLES IN POPULAR CULTURE

THE LIFE AND DEATH OF STARS

SMALLER STARS (LIKE OUR SUN)

( Don’t worry, we have around 5 billions years left yet … )

CHANDRASEKHAR LIMIT

• Discovered by Subrahmanyan Chandrasekhar • Awarded Nobel Prize for Physics 1983

• Maximum mass of stable white dwarf• 1.4 x mass of our Sun• Above that – Neutron star or Black Hole

TOLMAN–OPPENHEIMER–VOLKOFF LIMIT

• Calculated in 1939, derived from similar equations to the Chandrasekhar limit

• Maximum mass of neutron star• 2 - 3 x mass of our Sun ( from core remnant )• Original star mass 15 – 20 solar masses• Above that – Black Hole

ALL ABOUT MASS OF CORE REMNANT

< 1.4 Solar Masses = White dwarf

1.4 - ~3 Solar Masses = Neutron star

> 3 Solar Masses = Black hole

MASS OF ORIGINAL STAR

< 10 Solar masses = White dwarf

10 – 29 Solar masses = Neutron star

> 29 Solar masses = Black hole

SOME OTHER SCENARIOS….

• Some stars may just vanish to black hole instantly• Some huge stars blow up entirely, leaving NOTHING• Some may form Quark Stars

NEUTRON STAR

• All empty space of atoms squeezed away• Density of an atom core• Tight structure of neutrons• Matchbox of material = 13m tonnes• Cube of Earth 135m square

BLACK HOLE

• Core completely collapses in on itself• Mass compacts down to singularity• Infinite density• 1 dimension only• More on this soon…

• Event Horizon – giving black hole its name

VERY DENSE MASS…..

NON ROTATING BLACK HOLE

• “Schwarzschild Black Hole”• No spin, no electric charge

SINGULARITY

• Infinite density• 1 dimension – no real “size”• Space-time curves infinitely• Physics (esp relativity) breaks down entirely• Combined quantum & relatively MAY explain one day• No information can ever escape from singularity

EVENT HORIZON

• Shwarzschild radius – light can’t escape• = Event Horizon• No information can ever escape• ( Except Hawking radiation! )

• Past this boundary, space time curves inwards ONLY

GRAVITY – SPACETIME CURVATURE

GRAVITY – SPACETIME CURVATURE

GRAVITY – SPACETIME CURVATURE

GRAVITY – SPACETIME CURVATURE

NON ROTATING BLACK HOLE

• “Schwarzschild Black Hole”• No spin, no electric charge

ROTATING BLACK HOLE

• Inner / outer horizon• Static Limit• ”Location at which space-time is flowing at

the speed of light, making stationary particles that would be travelling at the speed of light”

• Ergosphere – region between the two

ROTATING BLACK HOLE

ACCRETION DISK & JETS

• Strong gravity bends light• Large scales, gravitational

lensing of distant galaxies• Similar around black holes• Interstellar

GRAVITATIONAL LIGHT DISTORTION

• Too close to event horizon, yes• At more distance, same pull as

original star• Replacing Sun with black hole

NOT VORACIOUS VACUUM CLEANERS!

• Micro • Solar Mass• Intermediate Mass • Super Massive

TYPES OF BLACK HOLE

• Micro:

TYPES OF BLACK HOLE

• Theoretical, never observed• May have been created shortly after Big Bang• May be created in particle accelerators• Exist for 10th of trillionth of trillionth seconds

• Solar Mass:

TYPES OF BLACK HOLE

• Ghost of massive stars• Size range approx 5 – 64 solar masses• ~ 100m within our galaxy, mostly invisible• Observable when in binary pair with star• Nearest 1600 light years away

TYPES OF BLACK HOLE

• Intermediate Mass:

TYPES OF BLACK HOLE

• Thought at center of some globular clusters

• Supermassive:

TYPES OF BLACK HOLE

• The true monsters!• Centre of all spiral

& elliptical galaxies• Largest 30bn – 40bn

solar masses!

MILKY WAY CENTRE – SAGITTARIUS A*

• 2 ly = 51Bn Km• Nearest star is 37 tr Km• Fits in 730 times!

MILKY WAY CENTRE – SAGITTARIUS A*

• Event horizon estimate 44 M km• 75% of distance of Mercury to Sun• Mass 4m Solar masses• Event Horizon Telescope – imminent!!

MILKY WAY CENTRE – SAGITTARIUS A*

• Avg – 0.1% mass of galaxy• Largest in relation to galaxy 4% – 14%!

SUPERMASSIVE BLACK HOLES

• Scientists not yet sure• Early galaxy gas clouds collapse• Stellar black hole eats and enlarge• Clusters of stellar holes combine• Merging of galaxies combines cores• Mystery how so big so early!

HOW FORMED?

• Ancient and distant• 12 billion light years away• Universe 1.8 bn years old

• But ENORMOUSLY bright!• Dust/Gas rich early galaxies,

accretion disks• > 200,000 known• Blasars are where jets point

at us!

QUASARS & BLASARS

GRAVITATIONAL WAVES

• Orbiting and merging of black holes

• Proposed by Einsten 1916• Detected LIGO 2015• Two 30 solar mass black

holes merging

GRAVITATIONAL WAVES

• eLISA – coming 2030! maybe…..

• Pathfinder sent 2015• Detect supermassive BH

mergers in early Universe• Observe 25k compact

binaries in Milky Way

WHAT HAPPENS TO YOU IF YOU GET CLOSE TO BLACK HOLE?

https://vimeo.com/8723702

Hawking Radiation

Something CAN escape the Event Horizon! .. maybe ……

DEATH OF A BLACK HOLE?

To come….

NEUTRON STARS?

Future talk ( There was so much to talk

about black holes! )

Ran out of time…..

QUESTIONS?