Hot Gas Halo Detected Around Galaxy NGC 4631
Is our Milky Way Galaxy
surrounded by a halo of hot gas?
A step toward solving this long-standing mystery
was taken recently with
Chandra X-ray observations of nearby galaxy
NGC 4631.
In the
above composite picture, newly resolved diffuse
X-ray emission is shown in blue, superposed on an
HST image
showing massive stars in red.
Since NGC 4631 is similar to the
Milky Way, this
observation indicates that our own Galaxy
is indeed surrounded by a halo of hot X-ray emitting gas,
although we are too close to clearly differentiate it from
more nearby extended X-ray sources.
The
clusters of massive stars
probably heat the halo gas.
Exactly how this gas gets ejected into a
halo is a topic of
continuing research.