Transcript No Slide Title
Today’s Comments
Graded papers – see Raquel to get old papers or tests.
Tests Lab Students: Lab Exam today, Apr. 16 D2L Quiz 10 available Observations Binoculars available for Moon Craters on your own. Fill out loan form.
Sunset Part 2. Work on this. Due Apr. 28 Telescopes, Star Gazing & Moon Craters available at UMN, Macalester and Eagle Lake Observatory – see dates on calendar Apr. 16, 17, 19, 24, 25, 28 & May 1 Space Exhibit at Science Museum of MN on 5:30-9pm, Thursday, May 7; Evite invitation coming tomorrow and you need to RSVP Answer EVITE – if you didn’t get this, see Raquel 3M & STEM free lunch with 3M Speaker, T3850, 12-1pm, Apr. 17
Black Holes
What is a black hole?
Special Theory of Relativity General Theory of Relativity What is gravity? How can it effect light?
How to make a black hole Structure (Singularity and Event Horizon) How to find a black hole
What is a Black Hole?
What is a Black Hole?
A black hole is a mass condensed so tightly that nothing, not even light, can escape from it’s gravitational effects.
Collapsed mass > 3 M Nothing can escape How can that be?
Mass of the star determines its fate mass < 1.4 M 1.4 M < mass < 3 M Possibly 3 to 8 M mass > 3 M Always for > 8 M Know This and the End of Life State
SPEED LIMIT 300 000 km/s
Special Theory of Relativity
Nothing in the universe
it’s the law!
can travel faster than the speed of light
SPEED LIMIT 300 000 km/s
Special Theory of Relativity (Special Relativity, SR) Tested many times in many ways.
http://www.exphy.uni-duesseldorf.de/ResearchInst/FundPhys.html
http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html
Newton’s Gravity
Law of Universal Gravitation
• Every mass attracts every other mass.
• Bigger masses bigger force • Bigger separation smaller force I. Newton D M m F F
F
G mM D
2
V
Launch V
Launch
V Launch =0
Launch Speed
V Launch
V
Launch V Launch
V Launch
V esc
2
GM V esc
2
GM D
Escape Speed
V
esc
2
GM r
Earth V esc = ~ 10 km/s
SUN
Escape Speed
V
esc
2
GM r
V esc = ~ 600 km/s
r ~ Moon size
Escape Speed
V
esc
2
GM r
V esc = ~ 15 000 km/s
3 M
Escape Speed
V
esc
2 – 3 MILES 2
GM r
3 M V esc
= 300 000 km/s
Speed
300 000 km/s
Limit
Nothing Escapes…. Not even light!
How can you crush 3 M into 2-3 miles?
Big Supernovas (hypernovas) Hypernova – explosion from very massive star collapsing into a black hole
Mass of the star determines its fate mass < 1.4 M mass < 3 M Possibly 3 to 8 M mass > 3 M Always for > 8 M Know This and the End of Life State
Mass of the star determines its fate Supernova Ia after white dwarf explodes Supernova II creates neutron star Hypernova creates black hole
How can you crush 3 M into 2-3 miles?
Hypernovas or
Lots of gas condensing
http://antwrp.gsfc.nasa.gov/apod/ap050402.html
Why doesn’t light escape from a black hole?
(or how can gravity pull on light?)
General Theory of Relativity
Gravity is
General Theory of Relativity Gravity is the curvature of space-time This is why masses attract!
Mass deforms space-time.
Sheet demo http://einstein.stanford.edu/content/education/EducatorsGuide/Page7.html
A second mass simply follows the curvature of space-time.
Coin wishing well demo http://einstein.stanford.edu/content/education/EducatorsGuide/Page7.html
Both mass
and light
follow the curvature of space-time.
Space is something!
Light travels at 300 000 km/s in it.
Masses warp it.
Has General Relativity been tested?
Many times – all positive
Tests of General Relativity • Mercury’s orbit precession • Light bent by gravity – Eclipse in 1919
Tests of General Relativity • Mercury’s orbit precession • Light bent by gravity – Eclipse in 1919 – Gravitational lensing - focusing of light from distant galaxy or quasar by an intervening galaxy; produces multiple images – Quasar – energetic black hole core of a distant galaxy
Einstein’s Cross quasar behind the center of a massive galaxy and displayed as a clover leaf http://apod.nasa.gov/apod/ap130102.html
Tests of General Relativity • Mercury’s orbit precession • Light bent by gravity – Eclipse in 1919 – Gravitational lensing - focusing of light from distant galaxy or quasar by an intervening galaxy; produces multiple images – Quasar – energetic core of a distant galaxy • Gravitational redshift – Lengthening of photon wavelength due to leaving a gravity field
Modern Examples of General Relativity – Continual Evidence • Gravity Probe A (1976) • Radio waves sent to Viking, Mars lander (1979) • Radio waves sent to Cassini, Saturn orbiting spacecraft, on other side of Sun (2003)
Cassini verifies General Relativity (space-time is curved).
Einstein’s equations work!
Modern Examples of General Relativity – Continual Evidence • Gravity Probe A (1976) • Radio waves sent to Viking, Mars lander (1979) • Radio waves sent to Cassini, Saturn orbiting spacecraft, on other side of Sun (2003) • Gravity Probe B, in Earth orbit (2011)
Gravity Probe B verifies General Relativity (space-time is curved and twisted).
Einstein’s equations work!
What happens inside a black hole?
As masses get closer, gravity gets stronger!
So the tighter you cram in mass, the stronger gravity gets!
Once 3 M
is crammed into 2-3 miles, no known force can stop further collapse.
All the mass collapses into a point of zero size called the singularity!
Singularity
A word about General Relativity
Weak field case Strong field case And Einstein’s equations
Singularity? All the mass is in 0 size?
Signal that our theories need some modification.
Quantum Gravity?
What is the structure of a Black Hole?
Singularity Event Horizon All mass condensed here 0 size?
Infinite density?
Limit!!!!!!!
Inside here Escape speed > speed of light
How massive are black holes?
• 1. Stellar mass (3-20 M ) • 2. Mid-mass (100-10 000 M ) • 3. Massive (Millions M )
If a black hole is black, how do you “see” one?
1. Binary “stars” Star and black hole orbiting each other.
Look for wobble in the spectral lines of a visible star. http://www.unm.edu/~astro1/101lab/lab9/lab9_C1.html
Example - Cygnus X-1
Super Blue Giant Wobble of spectral lines Indicate an unseen companion ~ 9
M
Source: http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html
If a black hole is black, how do you “see” one?
2. Accretion Disk Gas orbiting just outside the event horizon a. See X-Rays or UV from colliding matter b. See accretion disk
Cygnus X-1 Dark companion ~9 M
Strong X-ray source
Source: http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html
Bloated star Black Hole Accretion Disk http://antwrp.gsfc.nasa.gov/apod/ap080811.html
NGC 4261
X-rays!!!
Optical Image http://chandra.harvard.edu/photo/2003/ngc4261/ngc4261_scale.jpg
http://www.nasa.gov/centers/goddard/news/topstory/2004/0720donutcloud.html
If a black hole is black, how do you “see” one?
3. Jets Perpendicular to accretion disk
http://apod.nasa.gov/apod/ap130312.html
http://www.nasa.gov/centers/goddard/images/content/96922main_ngc426 1_hubble_m.jpg
X-Rays from radio jets in NGC4696
Composite Image Credit:
X-ray in red NASA / CXC /S.Allen (Kavli Inst., Stanford) et al.
; Radio in blue NRAO /G.Taylor ( VLA ); Infrared in green - NASA/ ESA /W.Harris ( McMaster Univ.
) http://antwrp.gsfc.nasa.gov/apod/ap060427.html
M87 center
Centaurus A http://heasarc.gsfc.nasa.gov/docs/cgro/images/epo/gallery/agns/index.html
Centaurus A Colour composite image of Centaurus A, revealing the lobes and jets emanating from the active galaxy’s central black hole. Image: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray).
Hercules A. Image Credit:
NASA , ESA , S. Baum & C. O'Dea ( RIT ), R. Perley and W. Cotton ( NRAO / AUI / NSF ), and the Hubble Heritage Team ( STScI / AURA )
If a black hole is black, how do you “see” one?
4. Gas, dust swirling around black hole (much further out than the accretion disk) – Doppler Effect to measure speed – Kepler’s Laws to calculate mass
~100 000 ly
Sombrero Galaxy
~100 billion stars
Inner 2000 LY contains 1 billion M
Andromeda Galaxy Inner 10 LY contains 20 million M
Milky Way Toward Sagittarius
Swirling gasses imply ~3 million M
at center
If a black hole is black, how do you “see” one?
5. Star near center of Milky Way – Doppler and Kepler
Video clip of S2 orbit around a black hole at Milky Way center: http://www.youtube.com/watch?v=u_gggKHvfGw Article here: http://www.eso.org/public/usa/news/eso0226/
Star S2 near central black hole in Milky Way S2 orbit is 15 years at 5000 km/s Implies central black hole of 3.7 million M
If a black hole is black, how do you “see” one?
6. Binary black holes merging Animation here: http://chandra.harvard.edu/ph oto/2006/a400/animati ons.html
25 000 ly separation 1200 km/s through gas http://antwrp.gsfc.nasa.gov/apod/ap060412.html
If a black hole is black, how do you “see” one?
7. Clumps of hot iron gas orbit at 30 000 km/s ( 1/10 c) Credits: NASA/Dana Berry, SkyWorks Digital http://spaceflightnow.com/news/n0501/10speedracing/
If a black hole is black, how do you “see” one?
8. Star ripped apart by black hole Source: http://chandra.harvard.edu/ photo/2004/rxj1242/
If a black hole is black, how do you “see” one?
9. Ultra Luminous X-Ray sources
If a black hole is black, how do you “see” one?
10. Space-time Dragging (twisting)
Ways to Detect Black Holes
1. Binary stars 2. Accretion disk 3. Jets 4. Gas, dust swirling well outside black hole 5. Star near center of Milky Way 6. Binary black holes merging 7. Clumps of hot iron gas in orbit 8. Star ripped apart by black hole 9. Ultra-luminous x-ray sources 10. Space-time dragging
Next Week
Tuesday: Star Groups, Galaxies and Groups of Galaxies Thursday: Galaxy Motion & Hubble’s Law