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Issue 6.02

The Astrophysics Spectator

January 28, 2009

Why do astrophysicists assume anything really massive is a black hole?  Why can't the massive things found at the centers of galaxies be just really massive neutron stars?  These are the questions addressed by a page added under the “Degenerate Objects” topic with this issue.

The evolution of objects into degenerate dwarfs and neutron stars resembles the tossing of stones towards the edge of a cliff.  Throw the stone lightly, and it lands at our feet.  Throw it a little harder, and it lands on the edge of the cliff.  These stones represent the objects that evolve into planets, brown dwarfs, and degenerate (white) dwarfs.  Throw a little harder, and the stone sails over the edge of the cliff, plunging down until it smacks into a ledge below.  This represents the objects with a little too much mass to be degenerate dwarfs; they collapse down to neutron stars, and when they smack the neutron star floor, they light up the sky as supernovae.  Now throw a stone as hard as you can, and it will go over the cliff edge and sail out beyond the ledge.  You would expect it to eventually hit the valley floor, making a big sound, but you hear nothing: there is no floor.  This is the situation with current theories of degenerate objects.  Objects that are too massive to become neutron stars collapse forever, becoming dimmer as the millennia pass, becoming black holes.

Why there is no floor underneath the most massive objects in our current theories and what must change in the theories to create a floor are described in the new page.  Whether nature herself puts a floor under all objects is an open question.

Also in this issue I explain why I believe the “stimulus” bill just passed by the U.S. House of Representatives will have a bad long-term effect on astronomy and astrophysics despite raising the amount of spending in these research fields over the next couple of years.

Next Update:  The next issue of the web site should appear on or shortly after February 11.

Jim Brainerd

Commentary

Scientific Pig-Out.  The American Physical Society is pleased with the bit of pork congress is giving the National Science Foundation and the National Aeronautic and Space Administration in the American Recovery and Reinvestment Act of 2009 that just passed the U.S. House of Representatives.  I explain why I believe their joy is misplaced, and why astronomy and astrophysics may see a long-term decline in funding because of increased government spending.  (continue)

Degenerate Objects

The Inevitability of Black Holes.  Astrophysicists generally assume that the compact objects at the centers of galaxies are black holes.  Why couldn't these objects be massive neutron stars or some other type of degenerate body?  The reason is that under general relativity and our current understanding of particle physics, no stable degenerate object can exist with more than about 5 solar masses.  Gravity would need to deviate from general relativity for million-solar-mass degenerate objects to exist.  (continue)

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