Black Holes v2

8/7/2019 Black Holes v2

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Black Holes in a Different LightDr. Jim Lochner (NASA/GSFC)



Outl ine

y Why Teach Black Holes?y If Black Holes Are Black, How Do We

See Them? ± Getting to Know Your X-ray Binary

y How Do We Know They are BlackHoles?

y Are There Any Web Resources Available?



Concep ts in Teaching B l ack Ho l e s

y The escape velocity of light from a star depends upon the star¶s mass and radius.

y Gravity is a basic force of nature created

between objects that have mass.y The speed of light, 300,000 km/s, is the

universal "speed limit."y The laws of motion and gravitation are utilized

to study the effects of black holes on their immediate environment.



(F rom: National Science Education Standards , National Academy Press,1998.)

Black Holes touch on topics in:y M otions and Forcesy Conservation of Energy and Increase in

Disorder y Interactions of M atter and Energyy The Origin and Evolution of the Universe

Con t en t S t andard s for Grade s 9-12:



S t andard s U s ed in Teaching Abo ut B l ack Ho l e s

(F rom: B enchmarks for Science Literacy , American Association for the Advancement of

Science, Oxford University Press, 1993. )

By the end of Grade 12, students should know that:

Increasingly sophisticated technology is used to learnabout the universe. Visual, radio, and x-ray telescopescollect information from across the entire spectrum of electromagnetic waves ; computers handle an avalancheof data and increasingly complicated computations to

interpret them; space probes send back data andmaterials from the remote parts of the solar system; andaccelerators give subatomic particles energies thatsimulate conditions in the stars and in the early history of the universe before stars formed.



If Black Holes are Black,How do We See Them ?





EM Spec t r u m

Electromagnetic Spectrum



O p t ica l

Optical images peer into central regions of other galaxies.







R adio

Radio tells us about motions of particles inmagnetic fields.

A portion of the Very Large Array, Socorro N M

Using many radiodishes allows us tosee small details



R adio Je ts from B l ack Ho l e s

M any black holes emit jets.y M aterial in jet moving at 0.9c.y Jet likely composed of electrons and positrons.

M agnetic fields surrounding black hole expelmaterial and form the jet.

y Interaction of jet material with magnetic fieldgives rise to Radio emission.



M87 - An E ll ip t ica l Ga l axy

With a curious feature



R adio s how s t he origin of t he Je t



Ou r pic tu re of wha t¶s happening

M agnetic field from surrounding disk funnelsmaterial into the jet





X -ray s from B l ack Ho l e s

In close binary systems, material flows from normal star toblack hole. X-rays are emitted from disk of hot gas swirlingaround the black hole.



P ower of Accre t ion

M aterial in Disk gains energy as it falls intoblack hole.y Gravitational energy is converted to kinetic

energy. ± Kinetic Energy is converted to heat and x-rays.

Up to 42% of the mass of infalling material isconverted into energy.y That¶s 10 38 erg/s ! (100,000x more than sun)



Ge tt ing t o Know yo u r X -ray Binary

The Groovy X-ray Binary M odel



How W e ll Do Know yo u r X -ray Binary ?

What force causes material to be pulled toward the black hole ?Gravity

Why is there a disk surrounding the black hole ?Gas flows according to rotational motion from orbit of star

What happens to the mass of the black hole as it takes inmaterial from the companion ?Black hole mass increasesHow much material is it ? (alot or a little ?)

A little (compared to mass of Companion Star)What makes it possible for us to ³ see´ the black hole ?

The disk emits X-rays



X -ray: A R o t a t ing B l ack Ho l e

We expect everything in the Universe to rotate. Non-rotating black holes are different from rotating ones.

Non-rotating black hole Rotating black hole

In GRO J1655-40, a 2.2 ms period was discovered. Thisimplies an orbit that is too small to be around a non-rotating black hole. This means the black hole is rotating.



X -ray: Frame Dragging

Detection of a periodin GRO J1655-40 dueto precession of thedisk.

This precessionperiod matches thatexpected for framedragging of space-time around the blackhole.

Credit: J. Bergeron, Sky & Telescope Magazine



X -ray: Je ts

Cen A is known to be a peculiar galaxy with strong radio emission.

Optical image of Cen A

Chandra image of Cen A

But it is also a strong X-rayemitter, and has an X-ray jet.



X -ray: M id ma ss b l ack ho l e s

Black Holes with massesa few hundred to a fewthousand times the mass of the sun have been found

outside the central regionsof a number of galaxies.

Often found in Starburstgalaxies.

� M ay be precursors to Active Galaxies.

Optical and X-ray images of NGC 253



Gamma ray

Compton Gamma-Ray Observatory

Gamma Rays reveal the highestenergy phenomena

Jets in active galaxiesemit gamma-rays as wellas radio.



Gamma ray

Active GalaxiesSeyferts - viewing the jet sidewaysy Gamma rays are extension of thermal

emission seen in X-ray.Blazars - looking down the jety Highly variable gamma-ray luminosity

y Gamma rays arise from lower energy photonsgaining energy from fast moving electrons inthe jet.



Differen t view s of s ame phenomena



How do we know t hey are b l ack ho l e s ?

M iddle mass black holes



B l ack Ho l e s in Binary S t ar Sy st em s

Black holes are often part of a binary star system - twostars revolving around eachother.What we see from Earth is a

visible star orbiting aroundwhat appears to be nothing.We can infer the mass of theblack hole by the way thevisible star is orbiting aroundit.The larger the black hole,the greater the gravitationalpull, and the greater theeffect on the visible star.

Chandra illustration





S u perma ss ive B l ack Ho l e s

Stars near the center of a galaxy have varied speeds and directionsof their orbital motions - that is termed their ³ v elocity dispersion.´

The cause of all this chaotic behavior appears to be a super-massiveblack hole that lurks at the galactic center!



M a ss e s of S u perma ss ive B l ack Ho l e s

Hubble Space Telescopecan precisely measure thespeed of gas and starsaround a black hole.It discovered a correlationbetween a black hole's massand the average speed of the stars in the galaxy'scentral bulge.The faster the stars are

moving, the larger the blackhole.



W eb R e s o u rce s, page 1

Imagine the Universe ± ³ An Introduction to BlackHoles´http://imagine.gsfc.nasa.gov/docs/science/know_l1/black_holes.html

Amazing Space ± ³ The Truth About Black Holes´http://amazing-space.stsci.edu/

Hubble Space Telescope Institutehttp://hubble.stsci.edu/news_.and._views/cat.cgi.black_holes

Adler Planertarium - ³ Astronomy Connections -Gravity and Black Holes´http://www.adlerplanetarium.org/education/ac/gravity/index.html

Gravity Probe B http://einstein.stanford.edu/



Constellation X-ray Observatoryhttp://constellation.gsfc.nasa.gov/ga/black_holes.html#what

Imagine the Universe: ³ You be the Astrophysicist´ -Determine the M ass of Cygnus X-1http://imagine.gsfc.nasa.gov/YBA/cyg-X1-mass/intro.html

Imagine the Universe ± ³ Taking a Black Hole for a Spin´http://imagine.gsfc.nasa.gov/docs/features/movies/spinning_blackhole.html

Starchild ±³Black Holes´http://starchild.gsfc.nasa.gov/docs/StarChild/universe_level2/black_holes.h

tml

³ Virtual Trips to Black Holes and Neutron Stars´http://antwrp.gsfc.nasa.gov/htmltest/rjn_bht.html




Universe! ± ³ Voyage to a Black Hole´http://cfa-www.harvard.edu/seuforum/explore/blackhole/blackhole.htm

Falling Into a Black Holehttp://casa.colorado.edu/~ajsh/schw.shtml

M assive Black Hole Information Center http://arise.jpl.nasa.gov/arise/infocenter/info-center.html

Everything you need to know about Black Holeshttp://www.astro.keele.ac.uk/workx/blackholes/index3.html

Black Holes in a Different Light (this presentation)http://imagine.gsfc.nasa.gov/docs/teachers/blackholes/blackholes.html


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Black Holes v2

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