This image from the Wide Field
Imager on the MPG/ESO 2.2-meter telescope shows part of the huge cloud
of dust and gas known as the Coalsack Nebula. The dust in this nebula
absorbs and scatters the light from background stars.
Credit: ESO
The Coalsack Nebula is located about
600 light-years away in the constellation of Crux. This huge, dusky
object forms a conspicuous silhouette against the bright, starry band of
the Milky Way and for this reason the nebula has been known to people
in the southern hemisphere for as long as our species has existed.
The Spanish explorer Vicente Yáñez Pinzón first reported the
existence of the Coalsack Nebula to Europe in 1499. The Coalsack later
garnered the nickname of the Black Magellanic Cloud, a play on its dark
appearance compared to the bright glow of the two Magellanic Clouds,
which are in fact satellite galaxies of the Milky Way. These two bright
galaxies are clearly visible in the southern sky and came to the
attention of Europeans during Ferdinand Magellan's explorations in the
16th century. However, the Coalsack is not a galaxy. Like other dark
nebulae, it is actually an interstellar cloud of dust so thick that it
prevents most of the background starlight from reaching observers.
A significant number of the dust particles in dark nebulae have coats
of frozen water, nitrogen, carbon monoxide and other simple organic
molecules. The resulting grains largely prevent visible light from
passing through the cosmic cloud. To get a sense of how truly dark the
Coalsack is, back in 1970, the Finnish astronomer Kalevi Mattila
published a study estimating that the Coalsack has only about 10 percent
of the brightness of the encompassing Milky Way. A little bit of
background starlight, however, still manages to get through the
Coalsack, as is evident in the new ESO image and in other observations
made by modern telescopes.
The little light that does make it through the nebula does not come
out the other side unchanged. The light we see in this image looks
redder than it ordinarily would. This is because the dust in dark
nebulae absorbs and scatters blue light from stars more than red light,
tinting the stars several shades more crimson than they would otherwise
be.
Millions of years in the future the Coalsack's dark days will come to
an end. Thick interstellar clouds like the Coalsack contain lots of
dust and gas -- the fuel for new stars. As the stray material in the
Coalsack coalesces under the mutual attraction of gravity, stars will
eventually light up, and the coal "nuggets" in the Coalsack will
"combust," almost as if touched by a flame.
Story Source:
The above post is reprinted from
materials provided by
ESO.
Note: Materials may be edited for content and length.
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