The Astrophysics Spectator

Issue 2.02, January 12, 2005

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January 12, 2005

We continue examining gravitational physics this week with the addition of a background page on stellar orbits in isotropic stellar clusters and a simulator page that displays the orbit of stars in the galactic plane of a spiral galaxy.

Stars are always grouped into galaxies. The motion of any one star within a galaxy is set by the collective gravitational field produced by all the other stars in the galaxy, but because the stars are in motion, the gravitational field can change. This self-interaction makes the evolution of a galaxy difficulty to study theoretically. The first step is to understand how stars orbit in the gravitational fields found in galaxies.

We begin our study of massive gravitational fields by presenting a page on the “Gravitational Physics” path that describe the orbits of stars in a general isotropic stellar system, and by presenting a simulator page that allows the reader to experiment with stellar orbits in the plane of a spiral galaxy.

Today's commentary is on intelligent design in the universe.

Jim Brainerd

Current News

Huygens Probe to Land on Titan. The Huygens probe, which was released from the Cassini spacecraft, is set to land on Titan, Saturn's largest moon, on the morning of January 14 (continue)

Current Commentary

The Lure of Intelligent Design. Intelligent design arguments for the existence of God have existed from ancient times. While the ancient arguments have fallen with the rise of scientific understanding, versions of the intelligent design argument still exist. (continue)

New Background

Isotropic Distribution Orbits. The Keplerian orbit is the orbit of a star around a point mass. If mass is distributed over a large area, the star's orbit is no longer Keplerian, but is generally open. This page, which is part of the “Gravitational Physics” path, presents the characteristics of these orbits. Two cases of particular interest are the orbits of stars in a uniform-density system, and the orbits of stars in a gravitational field with a strength that falls inversely with distance from the center of the system. (continue)

New Simulator Pages

Galactic Disk Orbit Simulator. A second simulator page is added to the “Gravitational Physics” path. This simulator models the orbits of stars in the galactic plane and the core of a spiral galaxy. (continue)


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