Copyright: ESA/Herschel/PACS/SPIRE/V. Roccatagliata (U. München, Germany)
The interstellar medium fills the ‘empty’ space between the stars in
our galaxy. It is a mix of molecular clouds, cold and warm gases,
regions of electrically charged hydrogen, and more.
Molecular clouds are the densest part of the interstellar medium, holding most of its mass in the form of hydrogen gas. ESA’s Herschel space observatory has revealed that many are built around filaments,
with dense threads snaking throughout each cloud. These filaments
potentially transport material, and, when massive enough, are known to
form new stars.
This Herschel image shows the Serpens Core, the
heart of a giant molecular cloud. The Core is the bright clump towards
the upper right, with a more diffuse secondary cluster, named Ser G3-G6,
shown at the bottom right. Also visible as a faint yellow glow towards
the upper left of the frame is a region known as LDN 583 that shines
brightly in the far-infrared.
Giant molecular clouds contain up to
10 million times the mass of the Sun, and can stretch for hundreds of
light-years. Compared to the rest of space they are dense, holding up to
a thousand atoms per cubic centimetre – and even more in star-forming
regions. However, these properties are relative: even at their densest,
these clouds are more than 10 times emptier than the best laboratory
vacuums we can produce on Earth.
These giant clouds are complex
formations, most often made up of filaments mixed with clumpy and
irregular folds, sheets and bubble-like structures. A typical spiral
galaxy like the Milky Way can contain thousands of them, accompanied by
many of their smaller relatives.
Serpens is an ideal target for
scientists wanting to know more about giant molecular clouds, because it
lies just 1400 light-years from us. Scientists compared Herschel’s
observations of this cloud to a state-of-the-art simulation to find out
more about the cloud’s properties, and to test the accuracy of their
model.
They discovered
a radial network of filaments stretching throughout the Serpens Core,
filaments that are predicted to break and fragment to form the cores of
new stars. These filaments resemble the spokes of a wheel, with the Core
forming the hub.
This three-colour image is made from
observations with Herschel’s PACS camera (blue and green) and SPIRE
camera (red). The size of the region shown is 1.7x1.9º on the sky, where
1º corresponds to about 25 light-years.
Source: ESA/Space in Images
