NGC 6369 before and after the AOF
The planetary nebula NGC 6563 observed with the AOF
The AOF + MUSE at work
The AOF + MUSE at work
UT4 and the AOF at work
The powerful lasers of the AOF
NGC 6369
ESO 338-4
The planetary nebula NGC 6563 observed with MUSE and the AOF
Videos
ESOcast 119: AOF First Light
NGC 6369 AO on/off crossfade
Image Comparisons
NGC 6369 with and without the AOF
NGC 6563 with and without the AOF
Spectacular improvement in the sharpness of MUSE images
The Unit Telescope 4 (Yepun) of ESO’s
Very Large Telescope (VLT) has now been transformed into a fully
adaptive telescope. After more than a decade of planning, construction
and testing, the new Adaptive Optics Facility (AOF) has seen first light
with the instrument MUSE, capturing amazingly sharp views of planetary
nebulae and galaxies. The coupling of the AOF and MUSE forms one of the
most advanced and powerful technological systems ever built for
ground-based astronomy.
The Adaptive Optics Facility (AOF) is a long-term project on ESO’s Very Large Telescope (VLT) to provide an adaptive optics system for the instruments on Unit Telescope 4 (UT4), the first of which is MUSE (the Multi Unit Spectroscopic Explorer) [1]. Adaptive optics
works to compensate for the blurring effect of the Earth’s atmosphere,
enabling MUSE to obtain much sharper images and resulting in twice the
contrast previously achievable. MUSE can now study even fainter objects
in the Universe.
“Now, even when the weather conditions are not perfect, astronomers can still get superb image quality thanks to the AOF,” explains Harald Kuntschner, AOF Project Scientist at ESO.
Following a battery of tests on the new system, the team of
astronomers and engineers were rewarded with a series of spectacular
images. Astronomers were able to observe the planetary nebulae IC 4406,
located in the constellation Lupus (The Wolf), and NGC 6369, located in
the constellation Ophiuchus (The Serpent Bearer). The MUSE observations
using the AOF showed dramatic improvements in the sharpness of the
images, revealing never before seen shell structures in IC 4406 [2].
The AOF, which made these observations possible, is composed of many parts working together. They include the Four Laser Guide Star Facility (4LGSF) and the very thin deformable secondary mirror of UT4 [3] [4].
The 4LGSF shines four 22-watt laser beams into the sky to make sodium
atoms in the upper atmosphere glow, producing spots of light on the sky
that mimic stars. Sensors in the adaptive optics module GALACSI
(Ground Atmospheric Layer Adaptive Corrector for Spectroscopic Imaging)
use these artificial guide stars to determine the atmospheric
conditions.
One thousand times per second, the AOF system calculates
the correction that must be applied to change the shape of the
telescope’s deformable secondary mirror to compensate for atmospheric
disturbances. In particular, GALACSI corrects for the turbulence in the
layer of atmosphere up to one kilometre above the telescope. Depending
on the conditions, atmospheric turbulence can vary with altitude, but
studies have shown that the majority of atmospheric disturbance occurs
in this “ground layer” of the atmosphere.
“The AOF system is essentially equivalent to raising
the VLT about 900 metres higher in the air, above the most turbulent
layer of atmosphere,” explains Robin Arsenault, AOF Project Manager. “In
the past, if we wanted sharper images, we would have had to find a
better site or use a space telescope — but now with the AOF, we can
create much better conditions right where we are, for a fraction of the
cost!”
The corrections applied by the AOF rapidly and continuously
improve the image quality by concentrating the light to form sharper
images, allowing MUSE to resolve finer details and detect fainter stars
than previously possible. GALACSI currently provides a correction over a
wide field of view, but this is only the first step in bringing
adaptive optics to MUSE. A second mode of GALACSI is in preparation and
is expected to see first light early 2018. This narrow-field mode will
correct for turbulence at any altitude, allowing observations of smaller
fields of view to be made with even higher resolution.
“Sixteen years ago, when we proposed building the
revolutionary MUSE instrument, our vision was to couple it with another
very advanced system, the AOF,” says Roland Bacon, project lead for MUSE. “The discovery potential of MUSE, already large, is now enhanced still further. Our dream is becoming true.”
One of the main science goals of the system is to observe
faint objects in the distant Universe with the best possible image
quality, which will require exposures of many hours. Joël Vernet, ESO MUSE and GALACSI Project Scientist, comments: “In
particular, we are interested in observing the smallest, faintest
galaxies at the largest distances. These are galaxies in the making —
still in their infancy — and are key to understanding how galaxies form.”
Furthermore, MUSE is not the only instrument that will
benefit from the AOF. In the near future, another adaptive optics system
called GRAAL will come online with the existing infrared instrument HAWK-I, sharpening its view of the Universe. That will be followed later by the powerful new instrument ERIS.
“ESO is driving the development of these adaptive
optics systems, and the AOF is also a pathfinder for ESO’s Extremely
Large Telescope,” adds Arsenault. “Working on the AOF has
equipped us — scientists, engineers and industry alike — with invaluable
experience and expertise that we will now use to overcome the
challenges of building the ELT.”
Notes
[1] MUSE is an integral-field spectrograph, a powerful instrument that produces a 3D data set of a target object, where each pixel of the image corresponds to a spectrum of the light from the object. This essentially means that the instrument creates thousands of images of the object at the same time, each at a different wavelength of light, capturing a wealth of information.
[3] At just over one metre in
diameter, this is the largest adaptive optics mirror ever produced and
demanded cutting-edge technology. It was mounted on UT4 in 2016 (ann16078) to replace the telescope’s original conventional secondary mirror.
[4] Other tools to optimise the operation of the AOF have been developed and are now operational. These include an extension of the Astronomical Site Monitor software that monitors the atmosphere to determine the altitude at which the turbulence is occurring, and the Laser Traffic Control System (LTCS) that prevents other telescopes looking into the laser beams or at the artificial stars themselves and potentially affecting their observations.
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 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts
Harald Kuntschner
ESO, AOF Project Scientist
Garching bei München, Germany
Tel: +49 89 3200 6465
Email: hkuntsch@eso.org
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Joël Vernet
ESO MUSE and GALACSI Project Scientist
Garching bei München, Germany
Tel: +49 89 3200 6579
Email: jvernet@eso.org
Notes
[1] MUSE is an integral-field spectrograph, a powerful instrument that produces a 3D data set of a target object, where each pixel of the image corresponds to a spectrum of the light from the object. This essentially means that the instrument creates thousands of images of the object at the same time, each at a different wavelength of light, capturing a wealth of information.
[4] Other tools to optimise the operation of the AOF have been developed and are now operational. These include an extension of the Astronomical Site Monitor software that monitors the atmosphere to determine the altitude at which the turbulence is occurring, and the Laser Traffic Control System (LTCS) that prevents other telescopes looking into the laser beams or at the artificial stars themselves and potentially affecting their observations.
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 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts
Harald Kuntschner
ESO, AOF Project Scientist
Garching bei München, Germany
Tel: +49 89 3200 6465
Email: hkuntsch@eso.org
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Joël Vernet
ESO MUSE and GALACSI Project Scientist
Garching bei München, Germany
Tel: +49 89 3200 6579
Email: jvernet@eso.org
Source: ESO/News
