OPEN WIDE: A retrofit at the Hobby-Eberly Telescope in Texas will broaden its field of view to take a census of galaxies just a few billion years after the big bang.
Image: Martin Harris/McDonald Observatory
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An experiment is gearing up in Texas to take on one of the universe's biggest mysteries by compiling a three-dimensional map of the early cosmos. The hope is that the survey will help inform astronomers and cosmologists about the nature of dark energy, a mysterious and hypothetical agent thought to constitute nearly three quarters of the universe's mass.
Dark energy is the term used by cosmologists to explain why the expansion of the universe is accelerating rather than slowing due to gravitation. Yet the name only hints at how little we know about it. Is dark energy a particle, a wave or a fundamental property of space-time? Has it always been there? Is it constant, or does it grow stronger as the universe expands? Hypotheses abound, but there is scant observational evidence to back them up. After all, it was not until 1998 that studies of distant supernovae provided the first solid evidence for a universe undergoing accelerated expansion.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is one of three ambitious projects aiming to provide those missing observations. The others are the Baryon Oscillation Spectroscopic Survey (BOSS), which achieved first light in September 2009 at the 2.5-meter Apache Point telescope in New Mexico, and the Dark Energy Survey (DES), which will add a digital camera with more than 500 megapixels to the Blanco four-meter telescope in Chile.
"Both BOSS and DES will refine our understanding of acceleration in the midlife universe, roughly five billion years ago," explains HETDEX project scientist Gary Hill of the University of Texas at Austin. "HETDEX goes further back. We are going to measure the expansion rate 11 billion years ago." Such observations fall in what might be called the adolescence of the 13.7-billion-year-old universe.
To elucidate the nature of cosmic expansion, HETDEX will map the positions of a million galaxies by measuring the spectrographic emissions of small, hydrogen-rich galaxies forming stars only 2.7 billion years after the big bang. "This is the sweet spot where dark energy should have enough effect so that it's detectable," Hill says.
Astronomers will use those observations to compare the distribution of galaxies five billion and 11 billion years ago and to determine whether the expansion rate has changed or remained constant over the eons. That should rule out some proposed explanations for dark energy.
Hill is retrofitting the 9.2-meter Hobby-Eberly Telescope, one of the world's largest optical telescopes, to run the experiment. Located in the Davis Mountains in western Texas, the telescope's primary mirror sits at a fixed angle while a moving instrument package above the mirror tracks its targets. Four optical correcting mirrors within the package reduce light sources to small, high-contrast images.
The HETDEX project plans to double the size of the 0.5-meter correcting mirrors and increase the mass of the hardware atop the telescope to roughly eight metric tons. When completed later this year, the upgrade will widen Hobby-Eberly's field of view by 30 times, to roughly half the area of the full moon. That augmentation will enable the telescope to capture data from large swaths of the sky, reducing the amount of calibration needed to correct for temperature, humidity and other atmospheric conditions when comparing one area of the sky to another.
A modular spectrograph, the first of its kind, will break down the light gathered by the telescope into its component wavelengths. Instead of building one large instrument, plans for HETDEX call for between 150 and 192 smaller modular spectrographs in four enclosures surrounding the telescope. Each spectrograph covers a small patch of the field of view; software then reassembles the complete spectral image from the individual parts.
Economics lie behind the modular approach. "Instead of one big instrument that would require a huge amount of engineering, we are taking a relatively simple spectrograph and replicating enough of them to drive the cost down," Hill notes. He originally expected per-unit bids to come in at half the $40,000 cost of his initial prototype, but so far they have been substantially lower.
Hill plans to spend a total of $34 million to retrofit the Hobby-Eberly Telescope for HETDEX, with nearly a quarter of the money being raised from private donors. That is far less than the cost of one large spectrograph, which in any case would have been too large to build onto Hobby-Eberly, he adds. The funds will pay for the spectroscopes and their temperature-controlled housings, as well as continued engineering, a new instrument package and reinforcements to bear the bulked-up assembly atop the telescope.
In addition to saving money, prototyping helped researchers assess performance and work out bugs before committing to a final design. "We really, really learned a lot about optical cable design," Hill says. At least 33,600 optical fibers will branch from the instrument package at the top of the telescope to the spectrographs below. One twist and a fiber will stop transmitting. "We had to invent new techniques to make it work," Hill says.
The prototype is currently installed on the neighboring 2.7-meter Harlan J. Smith Telescope. Because of its ability to capture a wide field of view and a broad spectrum of light, time on the instrument is already oversubscribed, says Hill's University of Texas at Austin colleague Karl Gebhardt.
The low-cost modular approach has attracted attention from researchers at other observatories, yet it has limitations. "When people build large, monolithic instruments, they configure them to do many different things," Hill notes. "Our system is designed to do one thing very well and at much less expense."
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28 Comments
Add CommentPart of me is fascinated with the idea of discovering new fundamental particles (waves?) populating our universe, but honestly all the talk about dark matter driving expansion smacks of the kind of stuff we heard before the discovery that there was no such thing as an ether.
Reply | Report Abuse | Link to thisRight now I'm waiting for the astronomers to come out and say 'Our bad, guys! It turns out the expansion was an error in our measurements. We were afraid something like that would happen. Well, guess it's back to tracking pulsars!'
aren't there alternative explanations to this observation (if correct) as related to gravitation pulls of other universes in a multiverse on "our" universe?
Reply | Report Abuse | Link to thisSearch not for the Dark Energy in the Cosmos. The Cosmos is a reflection of the Human Being. Root out the Dark Energy within your Heart and Dark Energy in the Universe will cease to disturb you. - BodhiRobin
Reply | Report Abuse | Link to thisWho can say for sure that time passes at a constant rate everywhere in the galaxy? There are no local measurements in our data from anywhere but here. How might a bubble of time distortion change the appearance of everything viewed outside it? Sci-Fi? Definitely a possibility. Outside the realm of possibilities? Hmmm. . .
Reply | Report Abuse | Link to this"There are more things under Heaven and Earth, Horatio, than are dreampt of in your philosophies."
There is some theory going around about that. The problem is, it's a religious theory. We can only test (at least for now) that which exists in THIS universe. As we most likely will never be able to determine what exists outside, if anything, it will remain forever untestable. So, we have to rely on that which we can see, test and verify.
Reply | Report Abuse | Link to thisBut, remember, science is about verifying predictions. One should be able to make predictions based on a sufficiently well designed theory. So, for example, the Big Bang Theory predicted the early universe was a very hot place. It predicted that as it expanded, the gas contained within would cool and we'd find the left over heat in the form of the cosmic background radiation exactly like that which was confirmed by WMAP. With evidence like that which backs up the BBT, alternative theorists have their work cut out for them to "debunk" it.
SpoonmanWoS, I agree with almost everything you said. The one exception is that instead of calling an untestable idea (such as the notion of a multiverse) a "religious theory", I would instead call it a "non-theory". If it doesn't make predictions, than it's not even a theory. From a scientific perspective, there may not be anything precluding it from being true, but it fails to meet the criteria needed for us to call it a "theory".
Reply | Report Abuse | Link to thisWhen describing people who firmly believe that it is true, despite having no evidence or theoretical basis for it, then I could see describing that belief as "religious". I hope you see the distinction I’m drawing.
It is my hope that the search includes a hunt for rapid non random wave function drop,it would be sign of someone else out there watching,and doing a two split experiment,that is causing wave function drop on our end, do too entanglement.It may not be the same star we see it coming from.It could be coming from another star that is same distance to the star that we are, as we are looking at.With both of us watching.With the photons arriving here and the other star at the same time.Setting up a two slit experiment on our end could allow for real time communications between us and them, using entanglement.As I have said before there may those out there that are already trying to talk to us using this method,but nobody on this end is listening,because they think it's impossible.Being just a few years ahead of us they would already know that life is on Earth,and have plotted same distance stars from them to us,allowing for entanglement communications.We need only do the same.
Reply | Report Abuse | Link to thisIts my understanding the only reason theres no ether is because Einstein eliminated it by verbal fiat in order to explain away the failure of the 1887 Michelson/Morely experiment.
Reply | Report Abuse | Link to thisDark energy, dark matter and dark force seem to me to be terms made up by cosmologists attempting to explain away the anomalies of the alleged big-bang.
Dark Energy as Invalid Observational Perspective
Reply | Report Abuse | Link to thisIMHO, it’s the silliest thing. Astronomers have been looking through the wrong end of the telescope, metaphorically.
They found that the more distant galaxies were ‘receding away from us’ faster than standard models predicted from redshift.
From that observation they concluded that the periphery of the currently observed universe is expanding faster than it is nearer in.
However, the light from the more distant galaxies was emitted long ago: its redshift indicates the expansion rate of the EARLY universe. The expansion rate has more recently diminished, consistent with the laws of physics.
Dark Energy represents the unidentified energy necessary to produce the proposed acceleration of the universe, beginning about 5B years ago, identified interpreting observations of type Ia Supernovae and their host galaxies. Those observations indicated that a set of galaxies about 10B light years away were further away than was predicted by standard cosmological models, whereas a set of galaxies about 5B light years away were not. The astronomers reporting these observations apparently concluded that the periphery of the universe is receding away from us at an accelerating rate.
I can only interpret those observations to indicate that it is the light from more distant galaxies emitted into the earlier universe that had been subjected to the greater expansion rates. As a result, I can only conclude that expansion has decelerated in accordance with the second law of thermodynamics. Based on this interpretation, the observation results were fundamentally misinterpreted due to the researchers’ improper spatially oriented perspective of the actually temporally developing universe.
It should be expected that extraordinary proof would be required of extraordinary explanations inconsistent with the most fundamental laws of physics. In practice, however, now that Dark Energy seems to have become well established, has withstood the test of time (for 10 years), alternative interpretations of the original observation results are no longer given consideration.
Why do we label it is as a energy rather than a fifth force. Will that make theory of everything more complicated or simpler.
Reply | Report Abuse | Link to thisThe universe we experience daily is filled with dark energ electrons from the Sun that causes the force of gravity as well as give us light to see by----they are just different regions of the electromagnet spectrum
Reply | Report Abuse | Link to thisPlease bear in mind your statement "Before the discovery that there was no such thing as ether," might be a little too simplistic. Bear in mind that what might be called for might simply be a redefinition of what was called "ether," a term used without apology by Einstein himself. In other words, we need to set aside the sophistry which allows us to substitute the term "dark matter" for "ether." Also bear in mind that this is possible because there can be no agreement as to what the characteristics of either of these forms of matter are likely to be. Both Einstein's speculation, based on solid math, and modern theory are bound to be overly simplistic, Occam's Razor not withstanding.
Reply | Report Abuse | Link to thisPlease define time for us, as you conceive it.
Reply | Report Abuse | Link to thisWhat we learn about this universe will eventually give us a fairly detailed picture as to the nature of other universes. Indeed, it is most likely that a clear picture of the nature of this universe entails predictions as to the nature of other universes that are involved with it.
Reply | Report Abuse | Link to thisFor example, I view a universe as an energy trap. Some configurations of energy remain in it, (so to speak), and other configurations are not involved with it at all. Such a formulation immediately entails speculation as to the mathematical constructs that would exist in alternative universes. This suggests that whereas our universe is described axiomatically in terms of a math based on the nature of light, there may well be parallel universes based theoretically on some other axiomatics and therefore invisible and undectable to us.
How can we find the thing that is dark with our common sense.Open our mind first. NIRVANA.....
Reply | Report Abuse | Link to thisjack.123...holy crap...that could work...the receiver/transmitter would need to be in deep space to minimize entanglements locally....i hope someone pursues....
Reply | Report Abuse | Link to thisjtdwyer...well put...
nirvana...looks like you finally gained a fan in bodhirobin....
just a side note...people(myself included) have a tendency to think of the universe as a sphere...it's not....
Gravitation is the weakest force known to physics by a very large measure compared with e.g. electric (electrostatic) forces, which have the same distance dependence. The strong and weak nuclear forces are restricted to nuclear dimensions and therefore irrelevant on cosmological scales. The utter wonder of the solar system is that it obeys the gravitational force quite precisely. Even the smallest electrical imbalance would greatly upset this. The solar system survives because of inertia, The force available per unit mass coupled to an electric charge is so infinitely greater than through gravity that it is easier and quicker to keep the electric charges nicely balanced to a tee. And so gravity is revealed.
Reply | Report Abuse | Link to thisIt has been known for 80 odd years that galaxies seem to rotate faster than gravity alone would allow. Ergo, dark mass must be responsible. My first question: Because of mass-energy equivalence, this dark mass need not be in material form - could it not be in an exotic energetic form?
My second question: going from what we know quite well, is it not possible that on a galactic scale the electric charge distribution could be less perfectly balanced than at the solar system scale and that the extra force to keep the galaxy stable could be electric. In the same vein, have electrical effects been excluded in respect of the so-called dark energy scenario?
Gravitation is the weakest force known to physics by a very large measure compared with e.g. electric (electrostatic) forces, which have the same distance dependence. The strong and weak nuclear forces are restricted to nuclear dimensions and therefore irrelevant on cosmological scales. The utter wonder of the solar system is that it obeys the gravitational force quite precisely. Even the smallest electrical imbalance would greatly upset this. The solar system survives because of inertia, The force available per unit mass coupled to an electric charge is so infinitely greater than through gravity that it is easier and quicker to keep the electric charges nicely balanced to a tee. And so gravity is revealed.
Reply | Report Abuse | Link to thisIt has been known for 80 odd years that galaxies seem to rotate faster than gravity alone would allow. Ergo, dark mass must be responsible. My first question: Because of mass-energy equivalence, this dark mass need not be in material form - could it not be in an exotic energetic form?
My second question: going from what we know quite well, is it not possible that on a galactic scale the electric charge distribution could be less perfectly balanced than at the solar system scale and that the extra force to keep the galaxy stable could be electric. In the same vein, have electrical effects been excluded in respect of the so-called dark energy scenario?
In our world we imagine that there could be only one influence on the development of "our" universe, and that has to be internal forces that are at play, like anti-matter and now the ever sought for dark matter and its cousin dark energy. Is there life outside of our universe? Does time, matter and space exist in infinity? Are there other universes that exist outside our very doorstep, I do believe that the existence of infinite universes and that we are a small fish, in a giant ocean, being pulled into a whale. I think that we will never find the illusive dark matter/energy, because it just does not exist and never has. Period! Remember, the world in not flat.
Reply | Report Abuse | Link to thisDoes Dark Matter/Energy exist? At looking at the EM spectrum that is said to extend till infinity that includes the aspects of sound, light, energy, and matter, would that, also, include the existence of heavier forms of matter and energy? Do we know how the em spectrum changes as we go further up into higher wave lengths? But! Does this matter have a direct effect on the motion of the ocean? If the universe is accelerating at a higher rate of speed and is being pulled apart, would we not think that there may be an outside force that is excreting force on matter in our universe? We want to believe that time is finite and it began with the birth of this universe. Are we the crown of creation, or the center of the universe? Is time, matter and space infinite and the sum of this universe finite? Is the number of universes in existence infinite? Are we a rouge universe being swallowed by a larger universe?
Reply | Report Abuse | Link to thisJust suppose: Since extremely red-shifted light still travels at the speed of light locally, it follows that propagation of electromagnetic energy a.k.a. photons is slowed by gravity in the vicinity of its accelerated time sphere but does not slow in absolute time. It could very well be that gravity is as grainy as the quantum mechanical world that constantly rearranges itself to account for the instantaneous and omnipresent influence of the weakest force where there is sufficient density to observe it in the first place. The rest is dark whatever..
Reply | Report Abuse | Link to thisIn a new theory dark energy is a combination of energy dark matter, called: "The Twin-Tori cosmological Model". In this model the shape of the universe is a torus of dark energy, which embeds a torus of dark matter. In the dark matter torus also the visible matter is located. From inside this dark matter torus we experience the universe, which shows us a "deceptive appearance" of the big bang. In fact the big bang is a expansion-dynamic, which belongs in a "double torus universe".
Reply | Report Abuse | Link to thisAbout this subject a few "papers" have been published in the viXra archive, since Sptember 1 2009. The appropriate weblinkscould be found on Dan Visser's website (independent cosmologist), who is the promotor of the "Twin-Tori cosmological Model" (www.darkfieldnavigator.com).
The comment given here, is meant to explain that dark energy is processing dark matter in three time-dimensions. Dark energy will not change over time. It is time itself, however in three time-dimensions, instead of the one time-dimension, which is related to the big bang. Dark energy exchanges energy with dark matter by an interactive "force for dark energy". It is tht force, which is derivated in a "formula" for dark energy force", lauched on April 4 2004 on Dan's website. He also published his "time-torus" in December 2008. As well a the "formula for dark energy force" as the "time-torus" were recognized by two English physicists (mathematicians), Christopher Forbes and colleaque, who mathematically transformed Dan's idea in a double torus of dark energy - dark matter torus".
Dan Visser, Almere, the Netherlands
How many years will it be before people look back upon such a statement as this and recognize its utter ridiculousness?
Reply | Report Abuse | Link to this"Dark energy is the term used by cosmologists to explain why the expansion of the universe is accelerating rather than slowing due to gravitation."
Gravitation is acceleration. (I suppose if you look at it backwards it could be a slowing, but that would be looking at it wrong.) Gravitation is evidence of the acceleration of the expansion of the universe. It is part of the expansion, not something opposed to it. There is no need to make up imaginary stuff (except for the sheer fun of bilking the public out of billions for an imaginary particle detector).
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Reply | Report Abuse | Link to thisDark energy don't exist.
Reply | Report Abuse | Link to thisDark energy is a mistaken of the redshift light.
The redshift acceleration is a redshifting of redshifted light, it's like compound interest you can look at your account in your bank, where your only $ 100 grow faster and faster year after year, with the compount interest only. In the start its grow slowly, but after few years you will see a beautiful acceleration of the depossited money.
The dark energy is therefore only a compount interest for the univesal redschifted light and nothing else.
There is no need for dark energy, gravity folds space into what could be imagined as a doughnut in spherical form with a theoretical gravitational singularity at the center. Much like a roller coaster driven by gravity as space expands the expansion slows(reaching the top of the hill), and as it crests the outside of the doughnut it falls back in on its'self and begins to accelerate. Because the fabric of space is folded when veiwed from within it appears linear. The expansion of space is not linear but curved so its' collaps is viewed as an expansion. As if a balloon was blown up to the point of inversion with the point of inversion determined by gravity.The accelleration of space and matter in it viewed as an accellerated expansion to the observer but would really become an expansion into singularity driven by the force of gravity. This is a repetitive inversion, meaning that it is cyclic with a frequency relative to the universal mass and gravity over time.This is the origin of and ending of the universe as we know it. To be born again as all matter passes threw the gravitational center point (aka big bang theory) and because of gravitational acceleration the enormous initial rate of expasion.(aka inflation theory) This theory I've developed explains the big bang, inflation, the slowing of expansion and the observed reacceleration of the universes' expansion. Unforunatly theorists develope a theory and when it doesn't conform to observations they try to develope explanations and exceptions to force the observations to fit the theory. If the theory doesn't fit the obsevations than most likely it is wrong. My theory fits the observations without the use of magic, adjustments or unseen forces.
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