BLACK HOLES:The Other Side of Infinity Presented by: Sarah Silva (SSU NASA) And Phil Plait
The show content • The Search for Black Holes • The Formation of Stellar-Mass Black Holes • Supermassive Black Holes • Travel Inside the Black Hole at the Center of the Milky Way
BLACK HOLES for educators • Section 1 - The Formation of Black Holes • Activity 1 - Aluminum Foil, Balloons, and Black Holes • Activity 2 - Building Perspectives with Active Galaxies • Section 2 - The gravity of the situation (around black holes) • Activity 3 - Black Hole Space Warp • Section 3 - Travel Inside the Black Hole at the Center of the Milky Way • Activity 4 - Science Fiction or Fact • Section 4 - The Search for Black Holes • Activity 5 – The Past, Present, and Future of Black Holes
Section 1 The Formation of Black Holes
First comes first • What is a black hole? • Not just a vacuum cleaner • If you take an object and squeeze it down in size, or take an object and pile mass onto it, its gravity (and escape velocity) will go up.
Schwarzschild BH Black Hole Structure • Schwarzschild radius defines the event horizon • Rsch = 2GM/c2 • Not even light can escape, once it has crossed the event horizon • Cosmic censorship prevails (you cannot see inside the event horizon)
So let’s do it, make our own BH • In groups of 3 collect the material in the front of the room. (material list on handout) • We will attempt to make a black hole with aluminum foil and balloons in this lab • But first create your red supergiant • Then….. • Follow the instructions on the handout.
Masses of Black Holes • Primordial – can be any size, including very small If >1014 g, they would still exist - could have masses smaller than that of the Sun • “Stellar-mass” black holes – must be at least 3 Mo ~1034 g – many examples are known • Intermediate black holes – range from 100 to 1000 Mo - located in normal galaxies – many seen • Massive black holes – about 106 Mo – such as in the center of the Milky Way – many seen • Supermassive black holes – about 109-10 Mo - located in Active Galactic Nuclei, often accompanied by jets – many seen
How do black holes form? • Stellar-mass black holes • Supernova: an exploding star. When a star with about 25 times the mass of the Sun ends its life, it explodes. • called a “stellar-mass black hole,” or a “regular” black hole • Stellar-mass black holes also form when two orbiting neutron stars – ultra-dense stellar cores left over from one kind of supernova – merge to produce a short gamma-ray burst.
How do black holes form? • Supermassive black holes • lurk in the centers of galaxies, and are huge • millions or even billions of times the mass of the Sun! • Most likely formed at the same time as their parent galaxies, but exactly how is not known for sure. • Astronomers think there is a supermassive black hole in the center of nearly every large galaxy, including our own Milky Way.
Monstrous black holes • At the heart of every galaxy lies a black hole, millions to billions times the mass of our Sun HST/NGC 4261 800 light years
Target Object of the Day • Normal galaxy • A system of gas, stars, and dust bounded together by their mutual gravity. VS. • Active galaxy • An galaxy with an intensely bright nucleus. At the center is a supermassive black hole that is feeding.
Building Perspectives with Active Galaxies • Each person is going to build their own personal active galaxy, with jets! • The materials are in the front of the class. • You don’t need to cut up anything, we have done that for you. • Just assemble your AG and fill out the worksheet. • DON’T WORRY. I will give you another handout to take home for your class.
Galaxies and Black Holes • Zooming in to see the central torus of an active galaxy. Jet Accretion disk Black Hole
Radio Lobe Galaxy Radio lobes Jet Accretion Disk
Two Views of an Active Galaxy View at 90o from Jet View at an angle to jet Radio Lobe Galaxy Seyfert Galaxy
Another view of an Active Galaxy Looking down the Jet From this view, we see the active galaxy emitting gamma rays and X-rays. Quasar 3C279 Blazar Galaxy
Where are black holes located? • Let’s think…. • They form from exploded stars… • We have one at the center of the Milky Way…. • The nearest one discovered is still 1600 light years away • Black holes are everywhere!
Evidence • Zooming in to see the stars in the central parsec of the Milky Way galaxy, orbiting around – the BH!
Evidence • This shows ten years worth of Prof. Ghez’ data at 2.2 microns of the stars orbiting around a 4 million solar mass black hole at the center of the Milky Way. • It also shows the star’s orbits extrapolated into the future Note: Stars S0-2 and S0-16 provide the best data
Section 3 Stars orbiting our central supermassive black hole
Section 2 The gravity of the situation (around black holes)
Black Hole Space Warp • In groups • Have two people hold the hoop horizontally. • Place the weight at the center of the hoop. • Have two people slowly toss in the bouncy balls one at a time. Toss them so that they are near the edge of the hoop when you release them. • Observe what happens to the path and the speed of the balls. • Repeat this 3 times.
Black Hole Space Warp • Record the following questions based on your observations. • What do the moving balls represent? • What does the weight represent? • What happened to the balls? • What does the blue latex material represent? • What happens to the material when the bouncy balls roll around?
How do black holes affect things near them? • Are we in danger of being gobbled up by a black hole? • The gravity from a black hole is only dangerous when you’re very close to it. • If the Sun were to become a black hole (don’t worry, it’s way too lightweight to ever do that), what size would it have to be? (remember activity 1) • Every few hundred thousand years, a star wanders too close to the black hole and gets torn apart. This produces a blast of X-rays that can be visible for decades!
How do black holes affect things near them? • Stars in the inner parts of a galaxy orbit the galactic center faster when the galaxy’s central supermassive black hole is more massive. • Astronomers conclude that the total mass of the inner region of a galaxy is proportional to the (relatively very small) mass of its central black hole! • It’s as if the formation of that black hole somehow affected the formation of the billions of normal stars around it.
What happens when you fall into a black hole? If you fall into a black hole You’re doomed. Sure, once you fall in you can never get back out, but it turns out you’ll probably be dead before you get there.
Section 3 Travel Inside the Black Hole at the Center of the Milky Way
Can black holes be used to travel through spacetime? • In reality, this probably won’t work. • While wormholes appear to be possible mathematically, they would be violently unstable, or need to be made of theoretical forms of matter which may not occur in nature.
Can black holes be used to travel through spacetime?They do it in the movies • Now we are going to look at a few movie clips. • While viewing the clips take notes about what is “Science Fact” and what is “Science Fiction.”
Section 4 The Search for Black Holes
What can we learn from black holes? • As matter falls into a black hole, it heats up and emits X-rays. • Current data indicate we may be missing as many as 80% of the black holes. • Unanswered questions: • What happens at the very edge of a black hole? • Where light cannot escape? • Where space and time swap places? • Where even Einstein’s General Relativity is stretched to the breaking point?
What can we learn from black holes? • Gravitational waves • ripples in the fabric of space • can teach us much about how gravity works • scientists even think gravitational waves were made in the Big Bang • LIGO and LISA may some day have some answers! LISA LIGO
Gravity Probe B (GP-B) Launched on April 20, 2004 • Gravity Probe B is the relativity gyroscope experiment developed by NASA and Stanford University to test two extraordinary, unverified predictions of Albert Einstein's general theory of relativity.
If black holes are black, how can we find them? • Binary star systems • measure the orbit of the normal star and determine the mass of the black hole • X-ray signatures • The first black hole, Cygnus X-1, was identified using data from the first X-ray satellite, Uhuru, in 1972 • NASA’s Chandra Observatory has found indications of black holes in practically every galaxy that it has studied in detail.
The Search for Black Holes Uhuru Explorer Satellite • First earth-orbiting mission dedicated entirely to celestial X-ray astronomy. • Launched on 12 December 1970 from Kenya (the name “Uhuru” is Swahili for freedom) • During its two year mission it created the first comprehensive and uniform all-sky X-ray survey. It expanded the number of known cosmic X-ray sources to more than 400. • Einstein Observatory • launched on November 13, 1978 • operated for more than two years. • first X-ray mission to use focusing optics and relatively high-resolution detectors. • saw for the first time X-ray jets from the supermassive black holes in the centers of galaxies Cen A and M87.
Hubble Space Telescope • Launched in April 1990 • Nicknamed “The Black Hole Hunter” • ability to see gas and stars very close to black holes in the centers of galaxies. • Able to confirm the presence of black holes in many nearby galaxies, and its observations were critical in the discovery that every large galaxy has a central supermassive black hole.
Chandra X-ray Observatory • Named in honor of the brilliant astronomer Subrahmanyan Chandrasekhar • Launched onboard the Space Shuttle Columbia on July 23, 1999 • Contribution to black hole astronomy is simply huge • Mapped thousands of black holes in nearby galaxies • Confirmed discovery of intermediate black holes, a new class of black holes with masses from 100 – 1000 times the mass of the Sun. • It has studied X-ray emission from the accretion disks around black holes, and the jets coming from them as well.
XMM-Newton Observatory • Measured iron in clumps of x-ray heated matter swirling around rotating black holes at 10% the speed of light. • Confirmed the signatures predicted near black holes by Albert Einstein's theory of Relativity in the light of the cosmic X-ray background. • Measured black holes spinning space around it like a flywheel. • Launched in December 1999 by European Space Agency (ESA).
Swift Explorer Satellite Launched November 20, 2004 • Has observed over 100 gamma ray bursts • The birth cry of black holes • Three coaligned telescopes to cover gamma-rays through visible light. • Has already made several major discoveries regarding GRBs. • Launch is featured in planetarium show.
GLAST ‘s main targets are active galaxies that emit gamma-ray jets – thousands are expected to be detected • GLAST will also look at supernovae, pulsars and GRBs within the energy range of 10MeV to 300GeV. • Planned for launch in 2007
Final Activity • With your students…. • We have provided handouts that have all of the information about the missions and observations previously mentioned. • Have them design a presentation about one or more of these missions or observations. LAT GBM
Wrap up • Section 1 - The Formation of Black Holes • Activity 1 - Aluminum Foil, Balloons, and Black Holes • Activity 2 - Building Perspectives with Active Galaxies • Section 2 - The gravity of the situation (around black holes) • Activity 3 - Black Hole Space Warp • Section 3 - Travel Inside the Black Hole at the Center of the Milky Way • Activity 4 – Science Fiction or Fact • Section 4 - The Search for Black Holes • Activity 5 – The Past, Present, and Future of Black Holes
Resources • The Black Hole education unit has resources listed in the appendix at the end of the guide.