August 16, 2001
Photo No: H2001-28a
Burst of Star Formation Drives Bubble in Galaxy's Core
These NASA Hubble Space Telescope snapshots reveal dramatic activities
within the core of the galaxy NGC 3079, where a lumpy bubble of hot gas
is rising from a cauldron of glowing matter.
The picture at left shows the bubble in the center of the galaxy's
disk. The structure is more than 3,000 light-years wide and rises 3,500
light-years above the galaxy's disk. The smaller photo at right is a
close-up view of the bubble. Astronomers suspect that the bubble is
being blown by "winds" (high-speed streams of particles) released
during a burst of star formation. Gaseous filaments at the top of the
bubble are whirling around in a vortex and are being expelled into
space. Eventually, this gas will rain down upon the galaxy's disk where
it may collide with gas clouds, compress them, and form a new
generation of stars. The two white dots just above the bubble are probably
stars in the galaxy.
The close-up reveals that the bubble's surface is lumpy, consisting of
four columns of gaseous filaments that tower above the galaxy's disk.
The filaments disperse at a height of 2,000 light-years. Each filament
is about 75 light-years wide. Velocity measurements taken by the
Canada-France-Hawaii Telescope in Hawaii show that the gaseous
filaments are ascending at more than 4 million miles an hour (6 million
kilometers an hour).
According to theoretical models, the bubble formed when ongoing winds
from hot stars mixed with small bubbles of very hot gas from supernova
explosions. Observations of the core's structure by radio telescopes
indicate that those processes are still active. The models suggest that
this outflow began about a million years ago. They occur about every 10
million years. Eventually, the hot stars will die, and the bubble's
energy source will fade away. Astronomers have seen evidence of
previous outbursts from radio and X-ray observations. Those studies
show rings of dust and gas and long plumes of material, all of which
are larger than the bubble.
NGC 3079 is 50 million light-years from Earth in the constellation Ursa
Major. The colors in this image accentuate important details in the
bubble. Glowing gas is red and starlight is blue/green. Hubble's Wide
Field and Planetary Camera 2 snapped this picture in 1998. The results
appear in the July 1, 2001 issue of the Astrophysical Journal.
Credits: NASA, Gerald Cecil (University of North Carolina), Sylvain
Veilleux (University of Maryland), Joss Bland-Hawthorn (Anglo-Australian Observatory),
and Alex Filippenko (University of California at Berkeley).