Relating basic properties of bright early-type dwarf galaxies to their location in Abell 901/902

Authors: F. D. Barazza, C. Wolf, M. E. Gray, S. Jogee, M. Balogh, D. H. McIntosh, D. Bacon, M. Barden, E. F. Bell, A. Böhm, J. A. R. Caldwell, B. Häussler, A. Heiderman, C. Heymans, K. Jahnke, E. van Kampen, K. Lane, I. Marinova, K. Meisenheimer, C. Y. Peng, S. F. Sanchez, A. Taylor, L. Wisotzki and X. Zheng
A&A 508, 665 (2009) Received 18 June 2009 / Accepted 16 October 2009
Keywords: galaxies: dwarf, galaxies: formation, galaxies: evolution, galaxies: clusters: individual: Abell 901/902, galaxies: structure

Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae

Authors: S. Kraus, K.-H. Hofmann, F. Malbet, A. Meilland, A. Natta, D. Schertl, P. Stee and G. Weigelt
A&A 508, 787 (2009) Received 26 July 2009 / Accepted 28 October 2009
Keywords: stars: pre-main-sequence, circumstellar matter, accretion, accretion disks, planetary systems: protoplanetary disks, planetary systems: formation, techniques: interferometric

Degeneracy Pressure

Jupiter and Saturn have a fundamental link
to the degenerate (white) dwarfs and neutron stars: all
of these objects are supported against gravitational
collapse by a pressure generated through the Pauli
exclusion principle of quantum mechanics.  This pressure
is called degeneracy pressure, and it acts through electrons
in planets, brown dwarfs, and degenerate dwarfs, and through
neutrons and protons in neutron stars.  It's existence is
directly linked to existence of chemical elements with
distinctive properties. 

Introduction to Degenerate Objects

Degeneracy pressure—the pressure caused by the Pauli
exclusion principle of quantum mechanics—is manifested by
four types of astronomical object: the giant gaseous planet,
the brown dwarf, the degenerate dwarf, and the neutron star.
The first-three objects constitute the subclass of degenerate
objects that are supported by electron degeneracy pressure.
The neutron star is the subclass of degenerate objects supported
by neutron and proton degeneracy pressure.  The degenerate
dwarf and the neutron star are two of the three endpoints
of stellar evolution (the third endpoint is the black hole).
Binary star systems containing a degenerate object are the
most brilliant systems in the Galaxy.

The Radii of Degenerate Objects

The radii of degenerate dwarfs and of neutron stars
are fundamentally linked to the fundamental constants
of physics.  The neutron star is about the size of
a black hole of comparable mass.  The degenerate dwarf,
on the other hand, has a radius that is of order 2,000 times
larger.  This difference in radius is a direct consequence
of the proton being more massive than the electron by this
factor.  The mass of the proton sets the absolute scale
for these objects.  The radius of the neutron star is of
order 15 km, and the radius of the degenerate dwarf
is comparable to Earth's.

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.

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.