Causes of a Galactic Fountain

Definition

• A galactic fountain is a fountain of hot gases that are expelled through a galaxy. These gases come from a supernova within the galaxy and are stored in a galactic bubble, or chimney, until they are forced outward. A galactic fountain is therefore caused by a series of supernovas.

History

• In 1976, Paul Shapiro and George Field first proposed the model of the galactic fountain. Joel N. Bregman detailed and expanded upon it in 1980. Shapiro continued work on the model and published work along with Robert A. Benjamin in 1991. By 1993, images taken by the German Rosat satellite were able to confirm many of the theories put forth by these scientists.

Significance

• The galactic fountain theory is one explanation for the existence of a galactic halo. The halo is the spherical area extending beyond the physical part of a galaxy. It is most visible in spiral galaxies where the shape of the halo contrasts the flat shape of the galaxy. The halo is the result of a complex series of reactions within a galaxy. The galactic disk, or the plane on which a galaxy sits, is interrupted by bubbles or chimneys that contain hot gases. These gases are the byproduct of supernova explosions throughout the galaxy. When the gases build up, they are expelled through the chimney, creating a galactic fountain of gases. The result of these galactic fountains is the galactic halo.

Theories/Speculation

• It is theorized that galactic fountains may be responsible for galactic storms. Many astronomers agree that these giant storms are the breeding grounds for new stars. Most believe that only the largest galaxies have potential for star-creating in this manner, since it would require about 40 supernovas in one small area over 10 million years for the force to be large enough to trigger a galactic storm. If this theory is true, stars act as a sort of fertilizer for their galaxies. Their demise becomes the fodder for future growth.

Identification

• The theory of galactic fountains became more solid since the ability to take detailed X-ray images of distant planets became possible. In 1993, images of NGC 891, a head-on disk galaxy about 30 million light-years from Earth, were the first to show evidence of galactic storms and fountains. The hot bubbles within the galaxy were clearly evident, as were the cooler areas surrounding it.