The Prawn Nebula from ESO's VST (wide crop)
Excerpts from a view of the Prawn Nebula from ESO's VST
The Prawn Nebula IC 4628 in the constellation of Scorpius
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The glowing jumble of gas clouds visible
in this new image make up a huge stellar nursery nicknamed the Prawn
Nebula. Taken using the VLT Survey Telescope at ESO’s Paranal
Observatory in Chile, this may well be the sharpest picture ever taken
of this object. It shows clumps of hot new-born stars nestled in among
the clouds that make up the nebula.
Located around 6000 light-years from Earth in the constellation of
Scorpius (The Scorpion), the nebula formally known as IC 4628 is a huge
region filled with gas and clumps of dark dust. These gas clouds are
star-forming regions, producing brilliant hot young stars. In visible
light, these stars appear as a blue-white colour, but they also emit
intense radiation in other parts of the spectrum — most notably in the
ultraviolet [1].
It is this ultraviolet light from the stars that causes the gas
clouds to glow. This radiation strips electrons from hydrogen atoms,
which then later recombine and release energy in the form of light. Each
chemical element emits light at characteristic colours when this
process occurs, and for hydrogen the predominant colour is red. IC 4628
is an example of an HII region [2].
The Prawn Nebula is around 250 light-years across, covering an area
of sky equivalent to four times that of the full Moon. Despite this huge
size it has been often overlooked by observers due to its faintness and
because most of its light is emitted at wavelengths where the human eye
is not sensitive. The nebula is also known as Gum 56, after the
Australian astronomer Colin Gum, who published a catalogue of HII
regions in 1955.
Over the last few million years this region of sky has formed many
stars, both individually and in clusters. There is a large scattered
star cluster named Collinder 316 which extends over most of this image.
This cluster is a part of a much larger gathering of very hot and
luminous stars. Also visible are many dark structures or cavities, where
interstellar matter has been blown away by the powerful winds generated
by the nearby hot stars.
This image was taken by the VLT Survey Telescope (VST) at ESO’s
Paranal Observatory in Chile. The VST is the largest telescope in the
world designed for surveying the sky in visible light. It is a
state-of-the-art 2.6-metre telescope built around the OmegaCAM camera
that contains 32 CCD detectors that together create 268-megapixel
images. This new 24 000-pixel-broad image is a mosaic of two such images
and is one of the largest single images released by ESO so far.
The picture forms part of a detailed public survey of a large part of the Milky Way called VPHAS+
that is using the power of the VST to search for new objects such as
young stars and planetary nebulae. The survey will also provide the best
images yet taken of many huge glowing star formation regions, such as
the one pictured here.
The very sharp VST images were further enhanced to bring out the
colour by including additional high quality imaging through other
filters taken by Martin Pugh, a very skilled amateur astronomer observing from Australia using 32-centimetre and 13-centimetre telescopes [3].
This press release represents a milestone — it is the 1000th press
release issued by ESO. The first one appeared in late 1985 and featured a
picture of Halley's Comet. They are all available online.
Notes
[1] This is the same kind of radiation
that causes unprotected human skin to burn when exposed to too much
direct sunlight. But the Earth’s atmosphere shields life on the surface
from most ultraviolet radiation and only longer wavelengths (between
about 300 and 400 nanometres) reach the ground and cause tanning and
burning of human skin. Some of the ultraviolet radiation emitted by very
hot stars in HII regions is at the much shorter wavelengths (shorter
than 91.2 nanometres) that can ionise hydrogen.
[2] Astronomers use the term “HII” (pronounced
“aitch-two”) to refer to ionised hydrogen, and “HI” (aitch-one) for
atomic hydrogen. A hydrogen atom consists of an electron bound to a
proton; in an ionised gas, atoms are split into freely-moving electrons
and positive ions — in this case the positive ions are just single
protons.
[3] More details of his observations can be found at Martin Pugh’s information page on this object.
More information
ESO is the foremost intergovernmental
astronomy organisation in Europe and the world’s most productive
ground-based astronomical observatory by far. It is supported by 15
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Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious
programme focused on the design, construction and operation of powerful
ground-based observing facilities enabling astronomers to make
important scientific discoveries. ESO also plays a leading role in
promoting and organising cooperation in astronomical research. ESO
operates three unique world-class observing sites in Chile: La Silla,
Paranal and Chajnantor. At Paranal, ESO operates the Very Large
Telescope, the world’s most advanced visible-light astronomical
observatory and two survey telescopes. VISTA works in the infrared and
is the world’s largest survey telescope and the VLT Survey Telescope is
the largest telescope designed to exclusively survey the skies in
visible light. ESO is the European partner of a revolutionary
astronomical telescope ALMA, the largest astronomical project in
existence. ESO is currently planning the 39-metre European Extremely
Large optical/near-infrared Telescope, the E-ELT, which will become “the
world’s biggest eye on the sky”.
Links
Contacts
Richard HookESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
