Unit 2 Seminar: Black Holes Evelyn I. Milian Instructor 2010 SC300: Big Ideas in Science

Unit 2 Seminar: Black Holes

Evelyn I. MilianInstructor

2010

SC300: Big Ideas in Science

Black Holes: Field Trip!

Visit one the following websites and come back to share your thoughts about them.

http://www.msnbc.msn.com/id/21134540/vp/10053354%2310053354; or if it takes too long to load go to: http://www.space.com/common/media/video/player.php?videoRef=black_holes

http://hubblesite.org/explore_astronomy/black_holes/

http://imagine.gsfc.nasa.gov/docs/ask_astro/black_holes.html

2010 Evelyn I. Milian - Instructor 2

http://www.msnbc.msn.com/id/21134540/vp/10053354%2310053354

http://www.msnbc.msn.com/id/21134540/vp/10053354%2310053354

http://www.space.com/common/media/video/player.php?videoRef=black_holes

http://www.space.com/common/media/video/player.php?videoRef=black_holes



Black Holes: Definition

Formed at the death of a very large star, a black hole is an object so dense, with a mass so concentrated, that nothing—not even light—can escape from its surface.


Black Holes – How They Form

One idea is that black holes are born out of death throes of giant stars.

Stars more than 10 times the mass of our sun end in explosions of unimaginable power. Temperatures soar to over one billion degrees. The pressure exerted by gravity is high enough so that the helium and carbon fuse into heavier elements; oxygen, silicon and sulfur fuse and eventually the nuclear reaction creates iron, the most tightly bound atomic nucleus, and the core stops burning. Then the star implodes under its immense gravity and becomes a supernova (a star’s luminous explosion). (PBS.org, 2006; Trefil; 2011).


The interior of a large star displays concentric shells of fusion reactions,

yielding progressively heavier elements toward the core. (Figure 14-18, Trefil)


The cores of large stars will eventually fill up with iron “ash”, and, no matter how high the pressure and temperature get, iron simply will not burn to produce a countervailing force to gravity. The iron core builds up until the force of gravity becomes too great and the core of the star collapses.

The striking NASA Hubble Space Telescope picture shows three rings of glowing gas encircling the site of supernova 1987A, a star that exploded in February 1987.


Figure 14-19, Trefil



Supernova 1987A: February 6, 1998

www.spacetelescope.org

Supernova ExplosionSource: NASA,

Hubble Space Telescope


What's left is a mass of sub-atomic particles, a neutron star, only about 10 miles across but of incredible density.

In fact it is so dense that a teaspoon of star matter will weight about 1 billion tons, if the mass is big enough, about 3 times the mass of our sun, it keeps collapsing, the result is a black hole. (PBS.org, 2006).

2010 7Evelyn I. Milian - Instructor

Black Holes – Gravitational Pull

The mass of the earth creates the gravity that pulls things to the ground.

With enough power we can escape the gravity and leave the earth behind.

But if you could take the earth and squeeze it to the size of a marble, the gravity on the surface would be much greater, not even a beam of light could escape.

This is what we call a black hole.


Black Holes – Gravitational Pull

Fortunately neither the Earth or our sun will ever become a black hole.

But they do exist and some are massive.

We can't see them but they can be detected by inference of objects, stars and light that surround them.


Black Holes – Structure

The three main components of a black hole are:

The Singularity (center),

The Schwarzschild Radius (given the name from the physicist that created it) which defines the size of the black hole, and

The Event Horizon, which is the surface of the black hole.



Black Holes – Singularity

What's at the center of a black hole?

We cannot glimpse what's inside a black hole because light or material can never reach us.

Current theories predict that all matter in a black hole is piled up at the center.

Understanding requires unsolved mystery of the fusion of the theories of gravity and quantum mechanics.


Black Holes – Radius

How big are black holes?

Astronomers have found black holes the size of 6 miles to the size of our solar system.

The Schwarzchild radius is proportional to the mass of the black hole.

To become a black hole the Earth would have to have a Schwarzchild radius of the size of a marble.


Black Holes – Event Horizon

The Event Horizon is an imaginary sphere that measures how close to the singularity (center) you can safely get.

Once you have passed the Event Horizon it becomes impossible to escape: you will be drawn in the black hole's gravitational pull and squashed into the singularity.


Black Holes – Where Are They?

Many researchers believe that the Milky Way is littered with black holes.

They are the dense remains of death stars.

But we don't see them because there is nothing there to light them up.

If they don't reflect light we can't see them.


Black Holes – Where Are They?

They may be invisible but to a visitor they will be specially deadly.

The density of a black hole is so strong that it distorts everything around them, including light. The tidal force is so strong that stretches everything until it separates mass at its molecular level.


Black Holes – Are They Real?

Astrophysicists generally agree that black holes exist.

There is good observational evidence from X-ray observations and from the Hubble Space Telescope that there are massive black holes (with masses more than a million times that of the Sun) that exist in the centers of some galaxies. (Jim Lochner for “Ask an Astrophysicist”; http://imagine.gsfc.nasa.gov)


http://imagine.gsfc.nasa.gov/

Black Holes – Are They Real?

In addition, there is also evidence for "galactic" black holes (so called because they are in our Galaxy), which result from the final stage of a star’s life. They are usually 3 - 10 times the mass of the Sun.

They also often orbit a companion star, and by observing the X-rays emitted from the region near the black hole and/or the visible light from the companion, a mass can be determined for the black hole.

If it is larger than the accepted mass for a neutron star (about 1.5 times the mass of the Sun), then astronomers generally agree the object is a black hole. There are quite a number of these objects known in our galaxy.


Jim Lochner for “Ask an Astrophysicist”;

http://imagine.gsfc.nasa.gov

http://imagine.gsfc.nasa.gov/

Black Holes – Images

Whirlpool Galaxy M51 (NGC 5149) taken by the Hubble Space Telescope.

Immense ring of dust and gas thought to surround and hide a giant black hole in the center of the galaxy.



This photograph shows a black hole that lies at the center of the galaxy M87.

A jet of electrons and other sub-atomic particles powered by the black hole to almost the speed of light.

This black hole has already consumed matter equal to about 2 billion of our suns. It lies 50 million light years from Earth.



Astronomers using NASA's Hubble Space Telescope have identified the source of a mysterious blue light surrounding a super-massive black hole in our neighboring Andromeda Galaxy (M31).

For more than a decade, astronomers have been puzzled by the strange light.



Hubble Space Telescope Uncovers Dust Disk Around a Massive Black Hole

Resembling a gigantic hubcap in space, a 3,700 light-year-diameter dust disk encircles a 300 million solar-mass black hole in the center of the galaxy NGC 7052.



Hubble Space Telescope Images.

Dust Disk Fuels Black Hole in Giant Elliptical Galaxy NGC 4261.



This Hubble photograph shows dozens of galaxies bound together by the gravity of a super-massive black hole, famous among astronomers for generating the most powerful outburst seen in the universe.


Hubblesite.org (2010). Gallery: Black Holes. http://hubblesite.org/gallery/album/query/black%20hole/pr1992027b/npp/all/

National Aeronautics and Space Administration (NASA). (2010). Imagine the Universe: Ask an Astrophophysicist –Black Holes. http://imagine.gsfc.nasa.gov/docs/ask_astro/black_holes.html

PBS.org. (2006). Monster of the Milky Way. A NOVA Production by Thomas Lucas Productions, Inc. for WGBH/Boston. http://www.pbs.org/wgbh/nova/transcripts/3314_blackhol.html

Spacetelescope.org. (2010). Hubble Space Telescope – Images. European Space Agency (ESA) and NASA. http://www.spacetelescope.org/images/archive/category/quasar/viewall/

Space Telescope Science Institute (STScl); supported by National Aeronautics and Space Administration (NASA). (2010). Black Holes: Gravity’s Relentless Pull.


http://hubblesite.org/explore_astronomy/black_holes/encyclopedia.html

Trefil, James & Hazen, Robert M. (2011). The Sciences An Integrated Approach. Sixth Edition. John Wiley & Sons, Inc. NJ, USA.

2010 Prof. Evelyn I. Milian 25

References


http://www.pbs.org/wgbh/nova/transcripts/3314_blackhol.html

http://www.spacetelescope.org/images/archive/category/quasar/viewall/

Documents

Unit 2 Seminar: Black Holes Evelyn I. Milian Instructor 2010 SC300: Big Ideas in Science