Neutron Stars, Pulsars, Black Holes

8/2/2019 Neutron Stars, Pulsars, Black Holes

1/30

Death of Stars

(for high mass stars)


2/30

Remember: What a star evolves into depends

on its MASS.

After the main sequence, a star could

become.

White dwarfs (low masssize of sun or smaller)

pulsars (heavier starslike blue giants)

black holes (heaviest starslike blue giants)


3/30

Review

Same as before, but faster

1. intersteller cloud of dust

2. protostar

3. main-sequence starbut as a BLUE GIANT

4. Red Supergiant-- When a high-mass star

exhausts the hydrogen fuel in its core the star leavesthe main sequence and begins to burn helium.


4/30


5/30

The Structure of the Core

of a Star Just Before It

Erupts as a Supernova

When helium is depleted, fusion of

heavier elements begins. This process iscalled nucleosynthesis.

H -> He -> C -> O -> Si -> Fe

(eventually goes to IRON)

When the final product is iron in the core,

no more energyso it collapses.


6/30

Why is iron (mass number = 56) the

last stage?

Atoms will

naturally fuse

into more

stable nuclei

You cant get

more energy

out of fusing

iron


7/30

B. Carbon core

contracts causing

1. Pressure to rise 2. Temp. to rise to 600

million K

C. Higher temps.Cause carbon fusion

cycle that will

eventually end in iron.


8/30

Steps in the Explosion of a Supernova

D. formation of iron ends the fusion cycle and starcontracts one last time and rebounds off the dense

core


9/30

Kaboom!

1. Luminosity--

100 billion times

brighter than thesun

2. produces wave

of neutrinos,

elements heavier

than Fe, shock

waves in nebulae


10/30

SN 1987A


11/30

Supernova

G. Example: SN

1987A

1. Where? --in LargeMagellanic Cloud (S.

hemisphere)

2. When?--1987 (duh)

3. What was found?--

neutrinosas the

theory predicted


12/30

Neutrino detector


13/30

The Brightness of a Typical Type II

Supernova for 100 Days After the Supernova

Reached Maximum Brightness


14/30

Neutron Stars

A. Description

1. Extremely dense star after

shedding outside layers

2. Mass is about 1.4 to 3

solar masses

3. Size is about 10 km

across (small!)

4. Density is about 3 x 1014g/cm3 ( 1cm3 of neutron star

equals 340 m3 of steel!!!)

(artists rendition)


15/30

Pulsars 1. Pulsars are neutron starsthat rotate

a. NOT normal starsthe

rotation period is 0.001 to

10 seconds (fast!)

2. Have extremely intense

magnetic fields

a. result--rips apart particles

at surface

b. accelerated electrons emitsynchotron radiation

c. like a lighthouse

3. Why do they spin?--

because big to small spinsfaster


16/30

A Model of a

Pulsar

We can maybe

see them if we

are lined up

with the

beams of

radiation


17/30

Crab Pulsar Animation


18/30

One Hundred

Consecutive Pulses

fromPSR 1133+16


19/30

Crab Pulsar

Ex. Crab Pulsar inside

the crab nebula

The pulsar is withinthe left over

supernova remnant

from 1054 A.D.


20/30

So What Effect does Gravity

have on spacetime? Spacetime has 4 coordinates:

x-axis, y-axis, z-axis (3-D) and time

Mass bends spacetime in general. (Einstein)

Black holes (supermassive) bend spacetime a

lot !


21/30

Flat and Curved Two-Dimensional Spaces

P th f M bl d th T l i i


22/30

Paths of a Marble and the Television

Image of the Paths for the Cases of

Flat and Curved Space


23/30

Black HolesA. Not really a holeB. A dense star that continues

to collapse

1. So dense and gravity is so

strong that light cant escape

C. Event horizon--ring around

black hole where lightcouldnt escape

D. Scharzshild radius--the

radius a star has to have to

become a black hole


24/30

Black holes

1. For sun to become a black hole--it would

have to collapse to at least 3 km

2. For the earth to become a black hole--it

would have to collapse to 1 cm

Th P th f Li ht R Ai d O t d


25/30

The Paths of Light Rays Aimed Outward

in Different Directions from the

Collapsing Core of a Star


26/30

A visual diagram of

how a black hole may

bend spacetime.

However, you dont

see this (its not like

a waterslide).


27/30

Artists drawing of a black hole If we cant see

them, how do we

know they are there?

1. Accretion disk 2. Galactic jets

3. X-rays from the

disk

4. A companion star

orbiting nothing

Note: The bright center is

not the black hole, justener etic material around it.

Galactic jets

Accretion diskX-rays


28/30

Cygnus X-1

Distance--2500 pc

(8000 ly away)

where?--inconstellation Cygnus

discovered in 1966

a. blue supergiant

companion that orbits

it

b. intense x-rays (as

seen in picture)

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


29/30

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


30/30

http://aspire.cosmic-

ray.org/labs/star_life/hr_interactive.html
http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.htmlhttp://aspire.cosmic-ray.org/labs/star_life/hr_interactive.htmlhttp://aspire.cosmic-ray.org/labs/star_life/hr_interactive.htmlhttp://aspire.cosmic-ray.org/labs/star_life/hr_interactive.htmlhttp://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html

Neutron Stars, Pulsars, Black Holes

Documents

Transcript of Neutron Stars, Pulsars, Black Holes