1. Evolution of stars, 1 solar and massive. Supernovae pulsars,
Phys 1830: Lecture 32
Making images! Wednesday April 8!!! 5:30pm Allen 536
M82 by Remi Lacasse
SEEQ
Images from the workshop!
Galactic wind i.e. fountain
Previous Classes:
Evolution of stars, 1 solar and massive.
Supernovae pulsars,
This Class
Light echos
gamma-ray bursts
Black holes
Upcoming classes
Galaxies – please review previous lectures
Cosmology.
Friday April 24 1:30pm
Frank Kennedy Gold Gym
Seats 1-135
ALL NOTES COPYRIGHT JAYANNE ENGLISH
Password?

2. Announcements w.r.t. Exam
1 more Office Hour Mon 3:00pm Allen 514
Contact me to see other times.
e.g. go over missed classes, review images
Exam:
1:30-3:30pm Friday April 24
Frank Kennedy Gold Gym seats 1-135
check Registrars’ website
about 70 questions
includes images
Pseudo-cumulative
doesn’t include planetarium exercise

3. Left is x-ray. Right is visual. Pulses 30 times a second.
Crab Nebula Movie
click audio speaker for pulses.
Also see the Vela pulsar at
Left is x-ray. Right is visual.
Pulses 30 times a second.
Formed in 1054 A.D.

4. Discovered by UM alumnus Ian Shelton. The first SN in the year 1987.
Supernova 1987a
Discovered by UM alumnus Ian Shelton. The first SN in the year 1987.
First naked-eye SN in ~380 years.
Occurred in a neighbouring satellite galaxy called the Large Magellanic Cloud.

5. Recall giant stars eject their outer envelopes!
We saw this in Antares.
Here’s some recent material.
Observations using the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed an unexpected spiral structure in the material around the old star R Sculptoris. This spiral is probably caused by a hidden companion star orbiting the star. This new ALMA video shows a series of slices through the data, each taken at a slightly different frequency. These reveal the shell around the star, appearing as a circular ring, that seems to gets bigger and then smaller, as well as a clear spiral structure in the inner material that it best seen about half-way through the video sequence.Credit:ALMA (ESO/NAOJ/NRAO)/M. Maercker et al./L. Calçada (ESO)
Slicing through the ejected shell.
Note spiral structure

6. SN 1987a
Recall giant stars like Antares eject their outer envelopes!
The movie is an HST 20th anniversary release at Hubblesite.
The ring consists of material ejected from the progenitor star thousands of years before it blew up.
The brightening of the ring occurs as the blast from the supernova interacts with the ejected material.

7. Light from SN 1987a interacts with dust in ISM.
Supernova light echo
AAT; David Malin
Light from SN 1987a interacts with dust in ISM.
Picture was made by photographically subtracting negative and positive images of plates of the region taken before and after the supernova appeared.

8. Supernova light echo Light moving outwards at constant speed.
CTIO/SuperMacho Team
AAT; David Malin
And
Also see Malin article in Sky and Telescope magazine for January, 1990 (p22)
Light moving outwards at constant speed.
Consider the light paths not along our line of sight.
Some of these intersect dust.
The light is reflected off the dust into our telescopes.
How the echo occurs for us on Earth can be derived using an ellipse with Earth at one focus and the SN at the other focus.

9. Supernova light echo
Patrick Tisserand and the EROS2 collaboration
The movie has been compiled with real images (it is not a simulation) : we used our 2 bands (called Red (~I filters) and Blue (V and R filter)) and a third colour has been created (linear association of the 2 others) to make a "true" colour movie. Many details, other than the light echoes, can be seen : a variable star in the top left corner (a Mira), clouds in the LMC, a Bok globul that is visible during a short time (north of SN87a) due to a higher surface brightness. The red colour that appears in the bottom right corner is due to a CCD artefact in the Red band.
Note that they make an “average” image out of their 2 filters which they colour green.
1200 images from July 1996 to February 2002 (~6.7 yrs)
Studies of light echos  accurate positions and dates of explosions.

10. Review
A light echo is light from a sudden burst that is reflected off of material such as dust. It occurs sometime after the direct light from the burst is received. The photons have not been absorbed by the dust and re-emitted.
True
False

11. Long Gamma Ray Bursts: Super Duper Supernovae
High energy burst lasting longer than about 2 seconds.
GRB are observed ubiquitously over the sky at a rate of about 1 a day.
Have occurred simultaneously, at the same position, with SNe in galaxies.
Formation scenario:
Stellar mass greater than solar masses.
Core collapses to form a black hole!
Core produces relativistic jets which punch their way through the imploding star  generating gamma rays.
“relativistic” == close to the speed of light.

12. Scientific American Diagram
Short Burst
Several scenarios- requres compact Merging neutron stars,
Several scenarios are possible - requires compact object, e.g. scenarios: merging binary neutron stars; merging black holes; merging black hole with neutron stars; flare from magnetar (SN core like neutron star with a very strong magnetic field); etc.
Long Burst

13. What kind of star will blow up?
Not all very massive stars create black holes – some are totally destroyed as matter and anti-matter annihilate.
Roughly 100 solar masses  gamma-ray burst. Actually a binary system.
Note the material ejected along the poles.
Roughly 7000 ly from Earth.

14. Eta Carina Simulations
Watch at:

15. What kind of stellar systems will blow up?
V445 Puppis: ESO Adaptive Optics
Not neutron stars merging, white dwarfs.
European Southern Observatory.
Double star system with bi-polar shells expanding at about 24 million kilometres per hour.
Changes in shell as some material from companion is accreted.
Recall one SN formation scenario is of white dwarfs merging.
Correct abundances of elements
 SN Type I

16. Which object above is most likely to form a black hole?
Review: a) b)
Which object above is most likely to form a black hole?
Object in image a)
Object in image b)

17. Review:
a) SN 1a progenitor
b) SN II progentior
b) is likely to become a gamma-ray burst due to a black hole forming in its core.

18. Discuss with your neighbour what you think a black hole is:
Black holes:
Discuss with your neighbour what you think a black hole is:
How do they form?
What is their structure?
How do we detect them?
Can anything escape from them?
What is gravity like near them? Are they a cosmic vacuum cleaner or not?
What are their sizes?
Puzzles?

19. What do you believe?
Nothing can escape from a black hole. No energy of any kind, no matter of any kind. Therefore once a black hole forms it can grow larger, by matter falling in, but it can never shrink.
True
False

20. What do you believe?
A black hole is like a cosmic vacuum cleaner, sucking things into it from exceedingly large distances away.
True
False

21. Black Holes: Definition
As an illustration, we collapse 4-D space-time to 2-D and embed it in 3-D space to show a shape; this is instead of using Einstein’s field equations equations which incorporate all dimensions and energy tensor (for energy + pressure).
Light needs to follow space-time, so it follows curved paths as well.
A region of space-time where the gravitation becomes overwhelming and the curvature of space-time is so great that space “folds” over on itself.

22. Black Holes: Definition:
Photon just outside a black hole.
These also lose energy.
Escape velocity is equal to or greater than the speed of light.
The escape velocity is the energy of motion required to overcome gravity and go into orbit.
 Matter and light cannot escape.
Even in the vicinity of a black hole, a photon moving away from it must give up energy. It does this, not by losing speed (that stays at 3 * 10**5 km/s), but by increasing its wavelength. (The energy of photon is E = h * frequency , where h is a constant. Contrast this with the energy of mass which is E= m c**2.)

23. Black Hole: components
Singularity: A point in the universe where the density of matter and the gravitational field are infinite.
Event Horizon: An imaginary spherical surface with a radius equal to the Schwarzschild radius, Rsch. Rsch is the distance from the centre of an object such that, if all the mass were compressed within that region, the escape speed would equal the speed of light.

24. Hold rubber sheet up high
Recall GR Table Demo:
Hold rubber sheet up high
collapse 4D spacetime into 2D and embed in 3D space to represent mathematics
GR reduces to Newton’s laws
A tennis ball gives a curve that generates gravitational pull well-represented by Newton’s laws.
nice orbits
Ball bearing on a handle represents dense object
Event Horizon plus curves described by Newton’s laws.

25. Black Hole: Components
Consider friction experienced by gas moving at relativistic speeds (i.e. close to the speed of light). This generates heat that radiates at X-ray wavelengths.
Can also have:
Accretion disk
Jets
Magnetic field lines

26. Black Holes: Accretion Disk
Tidal forces stretch stars apart or a companion star’s outer layers flow towards the black hole.
The stellar material orbits in a disk.
Crashing into itself, the stellar gas loses energy and orbits closer and closer to the event horizon.
Some material falls through the Event Horizon while some particles travel along the magnetic field lines, creating bi-polar jets.
How does it acquire an accretion disk? Tidal stretching approaching objects.
W.r.t. loss of energy, consider friction experienced by gas moving at relativistic speeds (i.e. close to the speed of light). This generates heat that radiates at X-ray wavelengths.
Note that tidal forces occur even in regions of space with only Newtonian gravity effects. So the splitting up of the star happens because such tidal forces are strong even before the star encounters the curvature of spacetime near the event horizon.

27. Black Holes: The size of the Event Horizon
Only depends on mass!
M of Jupiter/ M of Sun
= 2 * 10**27 kg/2 * 10**30 kg
= 10**(27-30)
= 10 ** -3 solar masses.
Rsch of Jupiter ~ 3 km * 10**-3
= 3 * 10**3 m/km * 10**-3
= 3 m
i.e. roughly the height of a room.
G is the gravitational constant, c is the constant speed of light. M is the mass.
You have to be very close to fall through the event horizon! The tidal radius is somewhat larger so you’d have started to stretch before this (like Comet Shoemaker-Levy) - the stretching near a black hole is called the toothpaste effect, since it is like squeezing a tube of toothpaste.
DO THIS CALCULATION FOR THE SUN!

28. Black Holes:
If our Sun became a black hole right now, what would happen to the orbit of the Earth.
a) Earth would get sucked into the black hole because black holes act like Cosmic Vacuum Cleaners.
b) Nothing since the force of gravity doesn’t change until one is close to the event horizon.

29. Black Holes: Inside the Event Horizon
According to General Relativity, time isn’t a particularly special dimension. This means it can be swapped with another dimension.
Outside the event horizon you can move in any direction in space but only 1 direction in time (towards the future).
Inside the event horizon you can only move forward in space towards the singularity but you can move backwards and forwards in time!
Moving backwards in time won’t get you out of the black hole anymore than me going to my home tonight will move me back to this morning when I left.

30. Place a black hole between you and a star:
Alain Riazuelo, IAP/UPMC/CNRS
Also check out the
“WIRED” article on “Interstellar” movie.
Note a very faint star in the middle of the image – place an intervening BH  2 images of the star.
Note the Milky Way and the Large Magellanic Cloud (LMC)

31. Black Holes: Can anything escape a black hole?
1. E.g. Roger Blandford: Mechanical energy can escape.
Threaded through the gas, in the accretion disk and falling into the black hole, are magnetic field lines.
The lines twist around the rotating black hole, slowing it down.
The energy of rotation travels out along the lines and is deposited in the disk  explains X-ray hot spots.
Use a scarf and tug on it. The energy of the tug travelling through the scarf is mechanical energy.