NGC 4631 (also known as the
Whale Galaxy or
Caldwell 32) is a
barred spiral galaxy in the
constellationCanes Venatici. This galaxy's slightly distorted wedge shape gives it the appearance of a herring or a whale, hence its nickname.
[3] Because this nearby galaxy is seen edge-on from
Earth, professional astronomers observe this galaxy to better understand the gas and stars located outside the plane of the galaxy.
NGC 4631 contains a central
starburst, which is a region of intense
star formation. The strong star formation is evident in the emission from
ionizedhydrogen[4] and
interstellar dust heated by the stars formed in the starburst.
[5] The most massive stars that form in star formation regions only burn hydrogen gas through
fusion for a short period of time, after which they explode as
supernovae. So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This
superwind can be seen in
X-rays[6] and in
spectral line emission.
[4] The gas from this superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.
[7] 
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