|Picture Scramble # 30
||30 August 2000
An Expanding Bubble in Space
An amazing hidden universe revealed by the Hubble Space Telescope.
Use the arrow keys to shift the image left, right, up or down.
Display Finished Picture Scramble
Astronomers, using the Wide Field Planetary Camera 2
on board NASA's Hubble Space Telescope,
imaged the Bubble Nebula (NGC 7635) with
The remarkably spherical "Bubble" marks the boundary between an
intense wind of particles from the star and the more quiescent interior of
the nebula. The central star of the nebula is 40 times more massive than
the Sun and is responsible for a stellar wind moving at
4 million miles per hour (7 million kilometers per hour)
which propels particles off the surface of the star. The bubble surface
actually marks the leading edge of this wind's gust front, which is slowing
as it plows into the denser surrounding material. The surface of the
bubble is not uniform because as the shell expands outward it encounters
regions of the cold gas, which are of different density and therefore arrest
the expansion by differing amounts, resulting in the rippled appearance. It
is this gradient of background material that the wind is encountering that
places the central star off center in the bubble. There is more material to
the northeast of the nebula than to the southwest, so that the wind
progresses less in that direction, offsetting the central star from the
geometric center of the bubble. At a distance of 7,100 light-years from
Earth, the Bubble Nebula is located in the constellation Cassiopeia and
has a diameter of 6 light-years.
Credits: NASA, Donald Walter (South Carolina State University),
Paul Scowen and Brian Moore (Arizona State University) .
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