VISTA views the Trifid Nebula and reveals hidden variable stars (annotated)
The Trifid Nebula in the constellation of Sagittarius
Comparison of the Trifid Nebula in visible and infrared light
VISTA views the Trifid and reveals hidden variable stars (wider field view)
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Videos
Cross-fade video comparing views of the Trifid Nebula in visible and infrared light
New infrared view of the Trifid Nebula reveals new variable stars far beyond
A new image taken with ESO’s VISTA survey
telescope reveals the famous Trifid Nebula in a new and ghostly light.
By observing in infrared light, astronomers can see right through the
dust-filled central parts of the Milky Way and spot many previously
hidden objects. In just this tiny part of one of the VISTA surveys,
astronomers have discovered two unknown and very distant Cepheid
variable stars that lie almost directly behind the Trifid. They are the
first such stars found that lie in the central plane of the Milky Way
beyond its central bulge.
As one of its major surveys of the southern sky, the VISTA telescope at
ESO’s Paranal Observatory in Chile is mapping the central regions of
the Milky Way in infrared light to search for new and hidden objects.
This VVV survey (standing for VISTA Variables in the Via Lactea) is also returning to the same parts of the sky again and again to spot objects that vary in brightness as time passes.
A tiny fraction of this huge VVV dataset has been used to create this
striking new picture of a famous object, the star formation region
Messier 20, usually called the Trifid Nebula, because of the ghostly dark lanes that divide it into three parts when seen through a telescope.
The familiar pictures of the Trifid show it in visible light, where
it glows brightly in both the pink emission from ionised hydrogen and
the blue haze of scattered light from hot young stars. Huge clouds of
light-absorbing dust are also prominent. But the view in the VISTA
infrared picture is very different. The nebula is just a ghost of its
usual visible-light self. The dust clouds are far less prominent and the
bright glow from the hydrogen clouds is barely visible at all. The
three-part structure is almost invisible.
In the new image, as if to compensate for the fading of the nebula, a
spectacular new panorama comes into view. The thick dust clouds in the
disc of our galaxy that absorb visible light allow through most of the
infrared light that VISTA can see. Rather than the view being blocked,
VISTA can see far beyond the Trifid and detect objects on the other side
of the galaxy that have never been seen before.
By chance this picture shows a perfect example of the surprises that
can be revealed when imaging in the infrared. Apparently close to the
Trifid in the sky, but in reality about seven times more distant [1], a newly discovered pair of variable stars has been found in the VISTA data. These are Cepheid variables,
a type of bright star that is unstable and slowly brightens and then
fades with time. This pair of stars, which the astronomers think are the
brightest members of a cluster of stars, are the only Cepheid variables
detected so far that are close to the central plane, but on the far
side of the galaxy. They brighten and fade over a period of eleven days.
Notes
[1] The Trifid Nebula
lies about 5200 light-years from Earth, the centre of the Milky Way is
about 27 000 light-years away, in almost the same direction, and the
newly discovered Cepheids are at a distance of about 37 000 light-years.
More Information
More Information
These results were presented in a paper
entitled “Discovery of a Pair of Classical Cepheids in an Invisible
Cluster Beyond the Galactic Bulge”, by I. Dekany et al., recently
published in Astrophysical Journal Letters.
The team is composed of I. Dékány (Millennium Institute of
Astrophysics, Santiago, Chile; Universidad Católica de Chile, Santiago,
Chile), D. Minniti (Universidad Andres Bello, Santiago, Chile;
Millennium Institute of Astrophysics; Center for Astrophysics and Associated Technologies; Vatican Observatory, Vatican City State, Italy),
G. Hajdu (Universidad Católica de Chile; Millennium Institute of
Astrophysics), J. Alonso-García (Universidad Católica de Chile;
Millennium Institute of Astrophysics), M. Hempel (Universidad Católica
de Chile), T. Palma (Millennium Institute of Astrophysics; Universidad
Católica de Chile;), M. Catelan (Universidad Católica de Chile;
Millennium Institute of Astrophysics), W. Gieren (Millennium Institute
of Astrophysics; Universidad de Concepción, Chile) and D. Majaes (Saint
Mary's University, Halifax, Canada; Mount Saint Vincent University,
Halifax, Canada).
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 16 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the
United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical
project in existence. And on Cerro Armazones, close to Paranal, ESO is
building the 39-metre European Extremely Large Telescope, the E-ELT,
which will become “the world’s biggest eye on the sky”.
Links
Links
Contacts
Richard Hook
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
