Unit 2 seminar
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Unit 2 Seminar. SC300 Eric Bliss. Black Holes: What Are They?. Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant.

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Unit 2 Seminar

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Unit 2 seminar

Unit 2 Seminar

SC300

Eric Bliss


Black holes what are they

Black Holes: What Are They?

  • Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun.

  • If a star that massive undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant.

    • With no outward forces to oppose gravitational forces, the remnant will collapse in on itself.


Black holes what are they1

Black Holes: What Are They?

  • The star eventually collapses to the point of zero volume and infinite density, creating what is known as a " singularity".

  • Around the singularity is a region where the force of gravity is so strong that not even light can escape.

    • Thus, no information can reach us from this region. It is therefore called a black hole,

      • and its surface is called the “event horizon ".

      • http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html


If we can t see them how do we know they re there

If We Can't See Them, How Do We Know They're There?

  • Since black holes are small, and light that would allow us to see them cannot escape, a black hole floating alone in space would be hard, if not impossible, to see.

    • the photograph below shows the optical companion star to the (invisible) black hole Cygnus X-1.


If we can t see them how do we know they re there1

If We Can't See Them, How Do We Know They're There?

  • If a black hole passes through a cloud of interstellar matter, or is close to another "normal" star, the black hole can pull matter into itself.


Unit 2 seminar

  • What is the biggest obstacle to proving that black holes really do exist?


Unit 2 seminar

  • Astrophysicists generally agree that when the compact object in an X-ray binary system is shown to be more massive than about 3 times the mass of the Sun, then this compact object is a black hole beyond reasonable doubt.

  • http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/011120a.html


Unit 2 seminar

  • What kinds of evidence are there that they do?


Unit 2 seminar

  • 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) exist in the centers of some galaxies.

  • http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970805b.html


Unit 2 seminar

  • Given what you know about scientific inquiry, why is the lack of direct evidence for black holes a problem for scientists?

  • Steps of the scientific method…

    • 1. Name the problem or question

    • 2. Form an educated guess (hypothesis) of the cause of the problem and make predictions based upon the hypothesis

    • 3. Test your hypothesis by doing an experiment or study (with proper controls)

    • 4. Check and interpret your results

    • 5. Report your results to the scientific community


Unit 2 seminar

  • Why might black holes be important?

  • “If I have seen further, it is by standing on the shoulders of giants.” Sir Isaac Newton

  • Culture of exploration?


Unit 2 seminar

  • http://www.youtube.com/watch?v=EOi0xA9GvX8


Unit 2 seminar

  • How is the search for black holes similar to the quest to view microscopic objects?


If we can t see them how do we know they re there2

If We Can't See Them, How Do We Know They're There?

  • As the matter falls or is pulled towards the black hole, it gains kinetic energy, heats up and is squeezed by tidal forces.

    • The heating ionizes the atoms and they emit x-rays The X-rays are sent off into space before the matter crosses the Schwarzschild radius and crashes into the singularity.

      • Thus we can see this X-ray emission.


References

References

  • http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html


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