The bubble nebula is an example of a massive star with an
extremely strong solar wind embedded inside a large gas cloud. This
wind is moving at 2000 km per second (4 million miles per hour)
and has carved out a large bubble 7 light years in diameter within the
cloud. The wind slows as it hits the much denser gas cloud, creating
the surface of the bubble. The star responsible is the brightest star
within the bubble (the star with diffraction spikes in this photo) -
BD602522 also known as SAO20575. This blue star is 40 times more
massive than the sun but due to it's distance of 7100 light years, its
apparent magnitude is just 8.7. The star is not at the center of the
bubble. This is because the surrounding gas is not uniform and is much
denser at the top left - which slows down the solar wind much sooner.
At the top left of the gas cloud you can just make out some dense
clumps or columns of gas. These are similar to the famous columns in
the Eagle Nebula, but they are not being eroded as fast. The whole
nebula is glowing due to the intense ultra violet radiation from the
central star.
