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Dark Energy Camera, the highest-resolution camera ever built, has begun its quest to pin down the mysterious stuff that makes up nearly three-quarters of our Universe.
The Dark Energy Survey’s 570-million-pixel camera will scan some 300 million galaxies in the coming five years.
The goal is to discover the nature of dark energy, which is theorized to be responsible for the ever-faster expansion of the Universe.
Its first image, taken 12 September, focused on the Fornax galaxy cluster.
In time, along with its massive haul of individual galaxies, it will study 100,000 galaxy clusters – the largest stable structures we know of – and 4,000 supernovae, the bright dying throes of stars.
This enormous survey is a collaboration between US, UK, Brazilian, Spanish and German astronomers.
The phone box-sized Dark Energy Camera or DECam is mounted on the 4 m Victor M Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile’s Atacama desert.
The Dark Energy Survey's 570-million-pixel camera will scan some 300 million galaxies in the coming five years
DECam is particularly sensitive to red and infrared light, to better study cosmic objects as distant as eight billion light-years away.
More distant objects are moving away from us – and each other – faster than nearer objects, which causes a shift of their apparent color toward the red end of the spectrum – a “redshift”.
Careful studies of the shifted light from distant supernovae were what first demonstrated this expansion, leading to the 2011 Nobel Prize in physics.
What is believed to be causing this increase in the speed of expansion is called dark energy, making up more than 70% of the “stuff” of the Universe and the focus of the DECam’s mission.
Other efforts hope to get to the bottom of the mystery, including the Boss survey and a future space telescope dediated to the effort called Euclid.
But for now, Will Percival from the University of Portsmouth, a Dark Energy Survey collaborator, said DECam is an exciting prospect.
“This will be the largest galaxy survey of its kind, and the galaxy shapes and positions will tell us a great deal about the nature of the physical process that we call dark energy, but do not currently understand,” he said.
The survey will tackle the problem in four ways.
It will study the same kind of supernovae that led to the Nobel Prize, in a bid to unravel the “expansion history” of the Universe – when its expansion increased and decreased over billions of years.
It will also map out in 3D the distribution of galaxy clusters, measuring what are known as baryon acoustic oscillations – literally relics of the sound echoes of the Big Bang.
By counting the clusters and plotting out when they evidently formed, the survey can feed back to computer models that map out how we think the Universe organized itself in its earliest years.
And studies of the way galaxies and galaxy clusters bend passing light – in a process called weak gravitational lensing – will help to pin down the equally mysterious “dark matter” that is believed to make up more than 80% of the Universe’s mass.
DECam will now be run through a series of tests and will begin the official survey in December.
With each snapshot it acquires, it will see an apparent area of the sky 20 times larger than the full moon.
In its full five-year run, it should capture an eighth of the full sky.
“The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier,” said James Siegrist, associate director of science for high-energy physics at the US Department of Energy, which oversaw the instrument’s construction.
“The results of this survey will bring us closer to understanding the mystery of dark energy and what it means for the Universe.”
What is redshift?
• The term “redshift” arises from the fact that light from more distant objects shows up on Earth more red than when it left its source
• The color shift comes about because of the Doppler effect, which acts to “stretch” or “compress” waves from moving objects
• It is at work in the sound of a moving siren: an approaching siren sounds higher-pitched and a receding one sounds lower-pitched
• In the case of light, approaching objects appear more blue and receding objects appear more red
• The expansion of the Universe is accelerating, so in general, more distant objects are moving away from us (and each other, and everything else) more quickly than nearer ones
• At cosmic distances, the shift can profoundly affect the color – the factor by which the wavelength is “stretched” is called the redshift
Dark energy and dark matter mysteries
• Gravity acting across vast distances does not seem to explain what astronomers see
• Galaxies, for example, should fly apart; some other mass must be there holding them together
• Astrophysicists have thus postulated “dark matter” – invisible to us but clearly acting on galactic scales
• At the greatest distances, the Universe’s expansion is accelerating
• Thus we have also “dark energy” which acts to drive the expansion, in opposition to gravity
• The current theory holds that 73% of the Universe is dark energy, 23% is dark matter, and just 4% the kind of matter we know well
NASA’s Wide-Field Infrared Survey Explorer (WISE) space telescope has added to its list of spectacular finds, spotting millions of supermassive black holes and blisteringly hot, “extreme” galaxies.
The finds once lay obscured behind dust.
But WISE can see in wavelengths correlated with heat, seeing for the first time some of the brightest objects in the Universe.
The haul will help astronomers work out how galaxies and black holes form.
It is known that most large galaxies host black holes at their centres, sometimes feeding on nearby gas, dust and stars and sometimes spraying out enough energy to halt star formation altogether.
How the two evolve together has remained a mystery, and the WISE data are already yielding some surprises.
NASA's WISE space telescope has added to its list of spectacular finds, spotting millions of supermassive black holes and hot galaxies
WISE gives astronomers what is currently a unique view on the cosmos, looking at wavelengths of light far beyond those we can see but giving information that we cannot get from wavelengths we can.
Among its other discoveries, in 2011 WISE spotted in a “Trojan” asteroid ahead of the Earth in its orbit.
But with the latest results, WISE has come into its own as an unparalleled black hole hunter.
“We’ve got the black holes cornered,” said Daniel Stern of NASA’s Jet Propulsion Laboratory (JPL), lead author of one of the three studies presented on Wednesday.
Dr. Daniel Stern and his colleagues used the Nuclear Spectroscopic Telescope Array (Nustar) space telescope to examine the X-rays coming out of the black hole candidates spotted by Wise, presenting their findings in a paper to appear in Astrophysical Journal.
“WISE is finding them across the full sky, while Nustar is giving us an entirely new look at their high-energy X-ray light and learning what makes them tick,” he said.
The other two studies presented – one already published in Astrophysical journal and another yet to appear – focussed on extremely hot, bright galaxies that have until now remained hidden: hot dust-obscured galaxies, or hot-Dogs.
There are so far about 1,000 candidate galaxies, some of which can out-shine our Sun by a factor of 100 trillion.
“These dusty, cataclysmically forming galaxies are so rare WISE had to scan the entire sky to find them,” said Peter Eisenhardt of JPL, lead author of the paper describing WISE’s first hot-Dog find.
“We are also seeing evidence that these record-setters may have formed their black holes before the bulk of their stars. The <<eggs>> may have come before the <<chickens>>.”
The data from the WISE mission are made publicly available so that scientists outside the collaboration can also carry out their own studies, so the future will hold a wealth of studies from these extreme and otherwise hidden corners of the Universe.
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NASA Solar Dynamics Observatory captured a dark, planet-sized Death Star-like object flying close to the sun on Monday.
The black Jupiter-sized orb is briefly engulfed in light from the sun, then flies off into space.
A video edited from the Solar Dynamics Observatory’s photos inspired a wave of speculation on YouTube.
The imagery was captured by NASA’s space telescope and edited together by a YouTube user, Sunsflare, who challenged experts to explain the strange “visitor”.
Naturally, the space agency has a rather more ordinary explanation for the strange, black orb.
It’s not a visitor from another solar system – or a planet being born out of the surface of the sun, as others had speculated.
Instead, it’s a solar “prominence” or “filament” – a feature extending out from the sun which forms over the course of a day, and can extend hundreds of thousands of miles into space.
NASA Solar Dynamics Observatory captured a dark, planet-sized Death Star-like object flying close to the sun on Monday
Scientists are still puzzled as to why these features form. The “dark” parts are material cooler than the surrounding solar matter.
C. Alex Young, a solar astrophysicist at NASA’s Goddard Space Flight Centre said, in a reply to Sunsflare’s video: “Filaments appear to be dark because they’re coolerin relation to what’s in the background. When you look at it from the edge of the sun, what you see is this spherical object and you’re actually looking down the tunnel.”
NASA says: “A solar prominence (also known as a filament when viewed against the solar disc) is a large, bright feature extending outward from the Sun’s surface.
“Prominences are anchored to the Sun’s surface and extend outwards into the Sun’s hot outer atmosphere, called the corona.
“Scientists are still researching how and why prominences are formed.
“An erupting prominence occurs when such a structure becomes unstable and bursts outward, releasing the plasma.”
NASA Solar Dynamics Observatory frequently captures the phenomenon – although often as violent eruptions, rather than the eerie sphere of this week’s activity.
“It is not uncommon for prominence material to drain back to the surface as well as escape during an eruption,” says Holly Gilbert a Goddard solar physicist.
“Prominences are large structures, so once the magnetic fields supporting the mass are stretched out so that they are more vertical, it allows an easy path for some of the mass to drain back down.”
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One of Europe’s great astronomical ventures is coming to a close after the Planck telescope, which was put in space to map the oldest light in the Universe, has run out of the helium coolant that keeps it in full working order.
Engineers expect the observatory’s systems to start to warm from their ultra-frigid state in the coming days, blinding one of its two instruments.
Nonetheless, Planck has gathered more than enough data since its launch in 2009 to complete its mission goals.
“We have had a flood of data – much more data than originally anticipated, and now we are in the frantic phase,” revealed Jan Tauber, the European Space Agency’s (ESA) Planck project scientist.
“In a year’s time we have promised to deliver our maps and scientific papers, so we are feeling some pressure,” Jan Tauber said.
Planck was launched on the same rocket as ESA's other flagship space telescope, Herschel, on 14 May 2009
Planck’s quest has been to survey the Cosmic Microwave Background (CMB) – the “first light” to sweep out across space once a post-Big-Bang Universe had cooled sufficiently to permit the formation of hydrogen atoms.
Before that time, scientists say, the cosmos would have been so hot that matter and radiation would have been “coupled” – the Universe would have been opaque.
The CMB pervades the entire sky, and scientists can measure tiny temperature variations in it to glean information about the age, contents and shape of the cosmos.
Two American satellites have already done this, but Planck is much more sensitive and can make much more detailed maps, with higher resolution.
To do this, some of its light detectors have had to operate at the astonishingly low temperature of minus 273.05C – just a tenth of a degree above “absolute zero”, the lowest temperature theoretically possible in the Universe.
A layered system of coolers was used to get down to this temperature, exploiting an unusual effect of mixing two isotopes of helium (helium-3 and helium-4) to achieve the deepest chill.
But Planck’s store of the helium-3 refrigerant has now run dry and engineers have informed Planck’s science team that they will soon lose the use of the observatory’s High Frequency Instrument (HFI).
Without it, the CMB cannot be seen across all its frequency range.
This is expected to happen as soon as the weekend. A more formal statement on the status of Planck will then be released by ESA. This may come on Monday.
“We always knew we would eventually lose HFI and the helium has run down exactly when we thought it would – on the dot,” explained Dr. Jan Tauber.
Planck still has use of its Low Frequency Instrument, which can operate at slightly higher temperatures (-269.15C), and this will continue gathering data for another six to nine months.
This information will be used to further refine the CMB maps, the first of which should be made public in January 2013.
The mission has far exceeded its minimum requirements. These called for the CMB to be scanned across the full sky at least twice.
Thanks to uninterrupted science operations since the August of 2009, Plank has now acquired five scans of the full sky.
“I think we lost just one day,” Dr. Jan Tauber said.
“Planck has been perfect; we’ve never had a serious issue with the satellite or the instruments.”
The larger scientific community is eagerly awaiting Planck’s CMB analysis.
Past pioneers in the study of the Cosmic Microwave Background have earned a clutch of Nobel Prizes, and there is great optimism that the super-sensitivity of Planck will advance the field considerably.
One hope is that Planck could find firm evidence of “inflation”, the faster-than-light expansion that cosmologists believe the Universe experienced in its first, fleeting moments.
Theory predicts this event ought to have left its imprint on the way the ancient light is polarized. Establishing the presence of this signature, though, will be painstaking work and no definitive statements are likely to come from the Planck team on this issue before 2014.
“It’s a bittersweet moment; the prime phase of Planck’s observing will very soon be over, which is of course sad,” said Prof. Mark McCaughrean, head of ESA’s Research & Scientific Support Department.
“But we have far more data in the bag than expected and it’s excellent stuff. People analyzing it are really excited about what we’re going to learn about the early Universe, soon after the Big Bang.”
Planck was launched on the same rocket as ESA’s other flagship space telescope, Herschel, on 14 May 2009.
