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Frontiers in Science Public Lecture Series
Black Holes and Collapsed Stars: Our Galaxy and Its Neighbors
William C. Priedhorsky
Nonproliferation and International Security Division
On a dark New Mexico night, we see a sky that is not much changed
from a year ago or a century ago. The planets move around the constellations,
comets come and go, but the distant stars are steady, excepting a few
pulsing or eclipsing stars and the occasional nova. When astronomers
use satellites to study x-rays from the stars and galaxies, they see
a much more variable and violent picture, because x-rays let us see
directly into the most extreme places in our Universe: the black holes
and neutron stars that mark the death of stars. The discovery of these
objects in the 1960's and 70's was honored by the 2002 Nobel Prize
in Physics, awarded to Riccardo Giacconi. Thanks to two new x-ray observatories
in space, NASA's Chandra and the European Newton, we can study black
holes and neutron stars not just in our own Galaxy, but also in its
neighbors. Our own work has concentrated on the Milky Way's nearest
full-sized neighbor, M31 in Andromeda. This galaxy, visible in the
autumn sky, is the most distant object that we can see with the unaided
eye. With the new observatories, we have studied hundreds of x-ray
stars in M31, and understand the population of our neighbor, in some
ways, better than our own.
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