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There are few places in the sky
that contain the dramatic star clouds and nebulosities as in
this field, which includes the famous Lagoon Nebula M8 at the
bottom, and the bi colored Trifid Nebula M20 at the top of this
frame. North is up in this 3 degree field. Lets start here with
a cursory examination of the Lagoon nebula. Note one very prominent
feature in this 1 degree wide red cloud of nebulosity - the core
is much more magenta than the outer wreaths. This is because
of the extra blue hydrogen beta line that is more predominant
in the core close to the hot O/B stars in the central star cluster
NGC 6530. This brilliant cluster is rated at 4.6 magnitude, and
spans a substantial 15 arcminutes in size.
Moving to the left, we
find a red cloud of nebulosity at the edge of the field. This
is NGC6559 and appears as a separated part of what is actually
the same nebulous complex. Between M8 and M20 the Milkyway is
very intense, the brownish coloration due to insterstellar dust
in this region. Superimposed on this central patch is a few red
wisps known as Sharpless2-28, a very dim nebula in a very rich
field.
M20 is both the red and
blue parts of the bi colored nebula at the top half of this frame.
The reds are emsission and span about 10 arcminutes, while the
blue part is a bit smaller but then a dim halo of blue surrounds
the red part you can see in this image. The blue coloration is
caused by reflection of dust from local star light. And that
local star light is the cluster NGC6514, in the center of the
Trifid.
Look aga in carfully and
just to the lower right of the Trifid is another nebulous star
cloud, Sharpless2-26.
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