Dark Energy Survey Advances

by Paul Gilster on June 25, 2008

Figuring out what makes up 74 percent of the universe is no small matter. But the late 20th Century discovery that the rate of expansion of the universe is not slowing but accelerating makes the research all but imperative. The Dark Energy Survey is behind the construction of an extraordinarily sensitive camera that will be installed on the Cerro Tololo Inter-American Observatory (CTIA) 4-meter telescope in Chile, with the aim of creating an unprecedented sky survey to probe these questions.

Cerro Tololo 4-meter telescope

I’m looking at the original proposal for the DES survey as submitted to the National Optical Astronomy Observatory office (NOAO controls the Cerro Tololo site). The document calls the discovery of accelerated expansion ‘arguably the most important discovery in cosmology since the serendipitous detection of the cosmic microwave background radiation by Penzias and Wilson in 1965′ (it’s hard to argue with that!). And it goes on to state the challenge posed by dark energy in stark terms:

According to General Relativity, if the Universe is filled with ordinary matter, the expansion should be slowing down due to gravity. Since the expansion is speeding up, we are faced with two logical possibilities, either of which would have profound implications for our understanding of the fundamental laws of physics: (i) the Universe is filled with a completely new kind of stress-energy with bizarre properties (in particular, negative effective pressure), or (ii) General Relativity breaks down on cosmological scales and must be replaced with a new theory, perhaps associated with extra dimensions.

You can see why dark energy would be of interest not only to astrophysicists but to those looking into advanced propulsion. Are there clues here that, properly understood, could lead us to new technologies? Accounting for how dark energy works is currently the greatest challenge in astrophysics. We’re a long way from untangling it, but the implication that energies of a new order could become available to a sufficiently advanced civilization will keep dark energy research on our watchlist.

Image: The CTIO 4-meter Blanco telescope, which will be used in the Dark Energy Survey. In this photograph, the instrument is silhouetted against the Magellanic Clouds (at left) and the Milky Way, as seen from Cerro Tololo in Chile. This is not a composite image. It was taken by Roger Smith using a 2048×2048 scientific CCD which has much higher sensitivity than photographic film, revealing greater detail in exposures short enough (20 seconds) to eliminate star trails. The CCD, normally used on the telescope pictured, was temporarily mated to a Zeiss Distagon 40 mm f/4 lens by a “camera body” made in house. The only source of illumination is starlight. Credit line: Roger Smith/NOAO/AURA/NSF.

As for DES, the plan is to map 300 million galaxies through multiple filters in a field of 5000 square degrees, creating a galaxy map that should bring higher precision to current dark energy studies. We’re still early in the game here, but it’s encouraging to see that the pieces of glass for the camera’s five lenses have now been shipped from the US to France, where they will be shaped and polished. The largest lens is a meter in diameter, to be installed in a camera with 500 megapixel capability and a fast data acquisition system that can take images in 17 seconds.

So the long process of building the DECam (Dark Energy Camera) has begun, the lenses to be polished to the smoothness of a millionth of a centimeter. Using multiple, complementary methods of studying redshift distribution, gravitational lensing, the evolution of galactic clusters and type 1a supernova distances, the plan is to improve our measurement of dark energy through a catalog of galaxies far deeper than what is available in the Sloan Digital Sky Survey. Observations in Chile are scheduled to begin in 2011 and continue until 2016.

Adam June 26, 2008 at 1:02

Hi Paul

One thing I take from the “Dark Energy” studies is that we really don’t quite get what the Universe is about – there’s mysteries awaiting our probings yet. Gives me reason to hope we might crack puzzles like FTL and time-travel, and so forth.

With that thought, because Dark Energy is only apparent during a brief window of cosmic time it also makes me wonder if the Fermi Paradox is also a matter of being close to the beginning of the Universe, rather than anything to do with the ultimate fates of intelligent life. Perhaps, once we work out the cosmo-chemistry involved, we might find the two are more related than they currently seem to be?

Administrator June 26, 2008 at 9:04

Good point, Adam, and interesting to relate dark energy’s mysteries to the Fermi question. All it takes is a reading of the wonderful Laughlin/Adams book The Five Ages of the Universe to start putting Fermi into a truly chronological context, with a realization of how early in the game life currently is. I know you and I have talked about this book before — what a wonderful read, and a genuine stretch for the imagination!

reslez June 27, 2008 at 21:40

The DES project is very exciting. From my layman’s perspective I think it’s clear we have a poor understanding of gravity. On one end of the scale we have accelerating expansion in the universe where we don’t expect it, and on the other end we have the Pioneer anomaly causing apparent deceleration where we don’t expect it. The more data we can get, the better.

Mark Phelps June 28, 2008 at 4:08

Hi Paul,great photo any chance of a link to a high res copy?
Many thanks,
Mark

Administrator June 28, 2008 at 8:37

Mark, I just linked the photo in the story directly to a larger copy of same at the Cerro Tololo site. There are a couple of other versions there as well:

http://www.noao.edu/image_gallery/html/im0081.html

Mark Phelps June 28, 2008 at 13:41

Thanks Paul,great photo and a bit scary to think what is lurking behind the Blue
Horizon of our daily sky…

Mark

ljk July 28, 2008 at 1:43

Summary of the DUNE Mission Concept

Authors: Alexandre Refregier, Marian Douspis, the DUNE collaboration

(Submitted on 25 Jul 2008)

Abstract: The Dark UNiverse Explorer (DUNE) is a wide-field imaging mission concept whose primary goal is the study of dark energy and dark matter with unprecedented precision. To this end, DUNE is optimised for weak gravitational lensing, and also uses complementary cosmolo gical probes, such as baryonic oscillations, the integrated Sachs-Wolf effect, a nd cluster counts.

Immediate additional goals concern the evolution of galaxies, to be studied with groundbreaking statistics, the detailed structure of the Milky Way and nearby galaxies, and the demographics of Earth-mass planets.

DUNE is a medium class mission consisting of a 1.2m telescope designed to carry out an all-sky survey in one visible and three NIR bands (1deg$^2$ field-of-view) which will form a unique legacy for astronomy. DUNE has been selected jointly with SPACE for an ESA Assessment phase which has led to the Euclid merged mission concept.

Comments: 9 pages; To appear in Proc. of SPIE Astronomical Telescopes and Instrumentation (23 – 28 June 2008, Marseille, France)

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0807.4036v1 [astro-ph]

Submission history

From: Marian Douspis [view email]

[v1] Fri, 25 Jul 2008 09:30:50 GMT (353kb)

http://arxiv.org/abs/0807.4036

ljk July 28, 2008 at 1:44

The focal plane instrumentation for the DUNE mission

Authors: Jeff Booth, Mark Cropper, Frank Eisenhauer, Alexandre Refregier, the DUNE collaboration

(Submitted on 25 Jul 2008)

Abstract: DUNE (Dark Universe Explorer) is a proposed mission to measure parameters of dark energy using weak gravitational lensing The particular challenges of both optical and infrared focal planes and the DUNE baseline solution is discussed.

The DUNE visible Focal Plane Array (VFP) consists of 36 large format red-sensitive CCDs, arranged in a 9×4 array together with the associated mechanical support structure and electronics processing chains. Four additional CCDs dedicated to attitude control measurements are located at the edge of the array. All CCDs are 4096 pixel red-enhanced e2v CCD203-82 devices with square 12 $\mu$m pixels, operating from 550-920nm. Combining four rows of CCDs provides a total exposure time of 1500s.

The VFP will be used in a closed-loop system by the spacecraft, which operates in a drift scan mode, in order to synchronize the scan and readout rates. The Near Infrared (NIR) FPA consists of a 5 x 12 mosaic of 60 Hawaii 2RG detector arrays from Teledyne, NIR bandpass filters for the wavelength bands Y, J, and H, the mechanical support structure, and the detector readout and signal processing electronics. The FPA is operated at a maximum temperature of 140 K for low dark current of 0.02e$-$/s. Each sensor chip assembly has 2048 x 2048 square pixels of 18 $\mu$m size (0.15 arcsec), sensitive in the 0.8 to 1.7 $\mu$m wavelength range.

As the spacecraft is scanning the sky, the image motion on the NIR FPA is stabilized by a de-scanning mirror during the integration time of 300 s per detector. The total integration time of 1500 seconds is split among the three NIR wavelengths bands. DUNE has been proposed to ESA’s Cosmic Vision program and has been jointly selected with SPACE for an ESA Assessment Phase which has led to the joint Euclid mission concept.

Comments: 9 pages; To appear in Proc. of SPIE Astronomical Telescopes and Instrumentation (23 – 28 June 2008, Marseille, France)

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0807.4037v1 [astro-ph]

Submission history

From: Marian Douspis [view email]

[v1] Fri, 25 Jul 2008 09:39:53 GMT (423kb)

http://arxiv.org/abs/0807.4037

ljk July 30, 2008 at 0:09

Is the Interacting Dark Matter Scenario an Alternative to Dark Energy ?

Authors: S. Basilakos, M. Plionis

(Submitted on 29 Jul 2008)

Abstract: We study the global dynamics of the universe within the framework of the Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the collisional Boltzmann equation, we can derive analytical solutions of the global density evolution, which can accommodate an accelerated expansion, equivalent to either the {\em quintessence} or the standard $\Lambda$ models. We also find realistic solutions in which the present time is located after the inflection point.

Comments: 4 pages, 1 figure. Submitted since 11 February 2008

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0807.4590v1 [astro-ph]

Submission history

From: Spyros Basilakos [view email]

[v1] Tue, 29 Jul 2008 07:39:48 GMT (150kb)

http://arxiv.org/abs/0807.4590

ljk March 17, 2011 at 14:13

Victor Blanco, Stargazer, Dies at 92

March 10th, 1918 to March 8th, 2011

by Dennis Overbye

March 16, 2011

The New York Times

Victor Blanco, a Puerto Rican astronomer who helped build a major outpost for American science, the Cerro Tololo Inter-American Observatory in Chile, and shepherded it through 14 years of revolution, counterrevolution and economic turmoil, died on March 8. He was 92 and lived in Vero Beach, Florida.

His death, near Vero Beach, was confirmed by his stepdaughter, Elizabeth Vitell.

Astronomers said Dr. Blanco would be remembered for his scientific, political and managerial skills as the observatory’s director in opening up the Southern sky as a new frontier of cosmic research.

When American astronomers worried that the election of a Marxist government under Salvador Allende in 1970 might threaten plans to build what would be the largest telescope in the Southern Hemisphere at the time — 158 inches in diameter — it was Dr. Blanco who was dispatched to explain to President Allende what the Americans were doing on his mountaintop.

And when President Allende was overthrown by a military junta and replaced by General Augusto Pinochet three years later amid death squads and disappearances, strikes and food shortages, Dr. Blanco was dispatched to General Pinochet, who decided that he wanted to visit the observatory and asked for a list of Chilean staff members and their political affiliations. Dr. Blanco demurred, saying that that would be an inappropriate intrusion into Chilean politics.

“General Pinochet visited Cerro Tololo anyway,” Dr. Blanco wrote in a summary of his life in The Annual Review of Astronomy and Astrophysics in 2001, “and we kept those Chilean staff members we knew to have been pro-Allende away.”

Through all the tumult, the observatory stayed open. The Southern sky offers many of the most exciting sights in the universe, like the center of our own Milky Way galaxy and its attendant star clouds and clusters. But historically most astronomers lived in the North and had little access to those Southern wonders.

Full article here:

http://philosophyofscienceportal.blogspot.com/2011/03/deceased-victor-blanco.html

Elaine Provancha September 15, 2012 at 15:33

Since the cosmic atmosphere is filled with so much more energy stress and speeding up all the time and our lives seem to be on the same course, at almost 88 years I SAY, ” GIVE ME THE GOOD OLD DAYS.” When we sat on the porch and conversed with family, when families ate dinner together, and checked on their neighbors everyday!

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