Map showing all galaxies in the local universe color-coded by their distance to us: blue galaxies are the closest, and red are farther, up to 300 million light-years away. Credit: University of Hawaii.
Researchers with the Cosmic Flows project have been working to map both visible and dark matter densities around our Milky Way galaxy up to a distance of 300 million light-years, and they’ve now released this new video map which shows the motions of structures of the nearby Universe in greater detail than ever before.
“The complexity of what we are seeing is almost overwhelming,” says researcher Hélène Courtois, associate professor at the University of Lyon, France, and associate researcher at the Institute for Astronomy (IfA), University of Hawaii (UH) at Manoa. Courtois narrates the video.
The video zooms into our local area of the Universe — our Milky Way galaxy lies in a supercluster of 100,000 galaxies — and then slowly draws back to show the cosmography of the Universe out to 300 million light years.
The map shows how the large-scale structure of the Universe is a complex web of clusters, filaments, and voids. Large voids are bounded by filaments that form superclusters of galaxies. These are the largest structures in the universe.
The team explains:
The movements of the galaxies reveal information about the main constituents of the Universe: dark energy and dark matter. Dark matter is unseen matter whose presence can be deduced only by its effect on the motions of galaxies and stars because it does not give off or reflect light. Dark energy is the mysterious force that is causing the expansion of the universe to accelerate.
Night time blast off of 4 stage NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload to study when the first stars and galaxies formed in the universe. The Black Brant soars above huge water tower at adjacent Antares rocket launch pad at NASA Wallops. Credit: Ken Kremer- kenkremer.com
Night time blast off of 4 stage NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload to study when the first stars and galaxies formed in the universe. The Black Brant soars above huge water tower at adjacent Antares rocket launch pad at NASA Wallops. Credit: Ken Kremer- kenkremer.com Updated with more photos[/caption]
WALLOPS ISLAND, VA – The spectacular night time launch of a powerful Black Brant XII suborbital rocket from NASA’s launch range at the Wallops Flight Facility on Virginia’s Eastern Shore at 11:05 p.m. June 5 turned darkness into day as the rocket swiftly streaked skyward with the Cosmic Infrared Background ExpeRiment (CIBER) on a NASA mission to shine a bright beacon for science on star and galaxy formation in the early Universe.
A very loud explosive boom shook the local launch area at ignition that was also heard by local residents and tourists at distances over 10 miles away, gleeful spectators told me.
“The data looks good so far,” Jamie Bock, CIBER principal investigator from the California Institute of Technology, told Universe Today in an exclusive post-launch interview inside Mission Control at NASA Wallops. “I’m very happy.”
Ignition of NASA Black Brant XII suborbital rocket following night time launch at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility at the eastern Virginia shoreline. The launch pad sits in front of the Antares rocket Launch Complex 0A dominated by the huge water tower. The rocket carried the CIBER astronomy payload to an altitude of approximately 358 miles above the Atlantic Ocean to study when the first stars and galaxies formed in the universe and how brightly they burned their nuclear fuel. Credit: Ken Kremer- kenkremer.com
The four stage Black Brant XII is the most powerful sounding rocket in America’s arsenal for scientific research.
“I’m absolutely thrilled with this launch and this is very important for Wallops,” William Wrobel, Director of NASA Wallops Flight Facility, told me in an exclusive interview moments after liftoff.
Wallops is rapidly ramping up launch activities this year with two types of powerful new medium class rockets – Antares and Minotaur V- that can loft heavy payloads to the International Space Station (ISS) and to interplanetary space from the newly built pad 0A and the upgraded, adjacent launch pad 0B.
“We have launched over 16,000 sounding rockets.”
“Soon we will be launching our first spacecraft to the moon, NASA’s LADEE orbiter. And we just launched the Antares test flight on April 21.”
I was delighted to witness the magnificent launch from less than half a mile away with a big group of cheering Wallops employees and Wallops Center Director Wrobel. See my launch photos and time lapse shot herein.
Everyone could hear piercing explosions as each stage of the Black Brant rocket ignited as it soared to the heavens to an altitude of some 358 miles above the Atlantic Ocean.
Seconds after liftoff we could see what looked like a rain of sparkling fireworks showing downward towards the launch pad. It was a fabulous shower of aluminum slag and spent ammonium perchlorate rocket fuel.
A powerful NASA Black Brant XII suborbital rocket streaks spectacularly into the night sky following its launch at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility at the eastern Virginia shoreline. The launch pad sits in front of the Antares rocket Launch Complex 0A dominated by the huge water tower. The rocket carried the Cosmic Infrared Background ExpeRiment (CIBER) to an altitude of approximately 358 miles above the Atlantic Ocean to study when the first stars and galaxies formed in the universe and how brightly they burned their nuclear fuel. Side firing thrusters have ignited to impart stabilizing spin as rocket ascends above launch rail. Credit: Ken Kremer- kenkremer.com
The awesome launch took place on a perfectly clear night drenched with brightly shining stars as the Atlantic Ocean waves relentlessly pounded the shore just a few hundred feet away.
The rocket zoomed past the prominent constellation Scorpius above the Atlantic Ocean.
In fact we were so close that we could hear the spent first stage as it was plummeting from the sky and smashed into the ocean, perhaps 10 miles away.
After completing its spectral collection to determine when did the first stars and galaxies form and how brightly did they shine burning their nuclear fuel, the CIBER payload splashed down in the Atlantic Ocean and was not recovered.
Time lapse view of night launch of NASA Black Brant XII suborbital rocket zooming past constellation Scorpius (left) at 11:05 p.m. EDT above Atlantic Ocean on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: Ken Kremer- kenkremer.comNight time launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: Ken Kremer- kenkremer.com
NASA said the launch was seen from as far away as central New Jersey, southwestern Pennsylvania and northeastern North Carolina.
One of my astronomy friends Joe Stieber, did see the launch from about 135 miles away in central New Jersey and captured beautiful time lapse shots (see below).
Time lapse view of June 5 launch of Blank Brant XII sounding rocket from Wallops Island as seen from Carranza Field in Wharton State Forest, NJ (about 135 miles north from Wallops). Scorpius is above the trees at the far left. Credit: Joe Stieber- sjastro.com
Everything with the rocket and payload went exactly as planned.
“This was our fourth and last flight of the CIBER payload,” Bock told me. “We are still analyzing data from the last 2 flights.”
“CIBER first flew in 2009 atop smaller sounding rockets launched from White Sands Missile Range, N.M. and was recovered.”
“On this flight we wanted to send the experiment higher than ever before to collect more measurements for a longer period of time to help determine the brightness of the early Universe.”
CIBER is instrumented with 2 cameras and 2 spectrometers.
“The payload had to be cooled to 84 Kelvin with liquid nitrogen before launch in order for us to make the measurements,” Bock told me.
“The launch was delayed a day from June 4 because of difficulty both in cooling the payload to the required temperature and in keeping the temperature fluctuations to less than 100 microkelvins,” Bock explained
The CIBER experiment involves scientists and funding from the US and NASA, Japan and South Korea.
Bock is already thinking about the next logical steps with a space based science satellite.
Space.com has now featured an album of my CIBER launch photos – here
Night launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT on June 5, 2013 from NASA Wallops Flight Facility, VA carrying CIBER astronomy payload. Credit: Ken Kremer
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
June 23: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8 PM
Aerial view of NASA Wallops launch site on Virginia shore shows launch pads for both suborbital and orbital rockets. CIBER’s Black Brant XII rocket blasted off just behind the Pad 0A water tower. This photo was snapped from on top of Pad 0B that will soon launch NASA‘s LADEE orbiter to the Moon. Credit: Ken Kremer- kenkremer.comNASA’s CIBER experiment seeks clues to the formation of the first stars and galaxies. CIBER blasted off on June 5 from the NASA Wallops Flight Facility, Virginia. It will study the total sky brightness, to probe the component from first stars and galaxies using spectral signatures, and searches for the distinctive spatial pattern seen in this image, produced by large-scale structures from dark matter. This shows a numerical simulation of the density of matter when the universe was one billion years old. Galaxies formation follows the gravitational wells produced by dark matter, where hydrogen gas coalesces, and the first stars ignite. Credit: Volker Springel/Virgo Consortium.NASA Time lapse view shows multiple stages firing during night launch of NASA Black Brant XII suborbital rocket at 11:05 p.m. EDT above Atlantic Ocean on June 5, 2013 from the NASA Wallops Flight Facility carrying the CIBER astronomy payload. Credit: NASA/Jamie AdkinsNASA Black Brant XII suborbital rocket streaks skyward after blastoff at 11:05 p.m. EDT on June 5, 2013 from NASA Wallops Flight Facility, VA carrying CIBER astronomy payload. Credit: Ken Kremer
NASA’s CIBER experiment seeks clues to the formation of the first stars and galaxies. It will study the total sky brightness, to probe the component from first stars and galaxies using spectral signatures, and searches for the distinctive spatial pattern seen in this image, produced by large-scale structures from dark matter. This shows a numerical simulation of the density of matter when the universe was one billion years old. Galaxies formation follows the gravitational wells produced by dark matter, where hydrogen gas coalesces, and the first stars ignite. Credit: Volker Springel/Virgo Consortium.
When did the first stars and galaxies form in the universe and how brightly did they burn?
Scientists are looking for tell-tale signs of galaxy formation with an experimental payload called CIBER.
NASA will briefly turn night into day near midnight along the mid-Atlantic coastline on June 4 – seeking answers to illuminate researchers theories about the beginnings of our Universe with the launch of the Cosmic Infrared Background ExpeRiment (CIBER) from NASA’s launch range at the Wallops Flight Facility along Virginia’s eastern shoreline. See viewing map below.
CIBER will blast off atop a powerful four stage Black Brant XII suborbital rocket at 11 PM EDT Tuesday night, June 4. The launch window extends until 11:59 PM EDT.
Currently the weather forecast is excellent.
The public is invited to observe the launch from an excellent viewing site at the NASA Visitor Center at Wallops which will open at 9:30 PM on launch day.
The night launch will be visible to spectators along a long swath of the US East coast from New Jersey to North Carolina; if the skies are clear as CIBER ascends to space to an altitude of over 350 miles and arcs over on a southeasterly trajectory.
Backup launch days are available from June 5 through 10.
Launch visibility map for the CIBER payload launch from NASA Wallops, Va, on June 4, 2013 at 11 PM EDT. Credit: NASA
“The objectives of the experiment are of fundamental importance for astrophysics: to probe the process of first galaxy formation. The measurement is extremely difficult technically,” said Jamie Bock, CIBER principal investigator from the California Institute of Technology
Over the past several decades more than 20,000 sounding rockets have blasted off from an array of launch pads at Wallops, which is NASA’s lead center for suborbital science.
The Black Brant XII sounding rocket is over 70 feet tall.
The launch pad sits adjacent to the newly constructed Pad 0A of the Virginia Spaceflight Authority from which the Orbital Sciences Antares rocket blasted off on its maiden flight on April 21, 2013.
“The first massive stars to form in the universe produced copious ultraviolet light that ionized gas from neutral hydrogen. CIBER observes in the near infrared, as the expansion of the universe stretched the original short ultraviolet wavelengths to long near-infrared wavelengths today.”
“CIBER investigates two telltale signatures of first star formation — the total brightness of the sky after subtracting all foregrounds, and a distinctive pattern of spatial variations,” according to Bock.
Preparing the CIBER instrument for flight. The optics and detectors are cooled by liquid nitrogen to -19C (77 K, -312F) during the flight to eliminate infrared emission from the instrument and to achieve the best detector sensitivity. Photo: NASA/Berit Bland
This will be the fourth launch of CIBER since 2009 but the first from Wallops. The three prior launches were all from the White Sands Missile Range, N.M. and in each case the payload was recovered and refurbished for reflight.
However the June 4 launch will also be the last hurrah for CIBER.
The scientists are using a more powerful Black Brant rocket to loft the payload far higher than ever before so that it can make measurements for more than twice as long as ever before.
The consequence of flying higher is that CIBER will splashdown in the Atlantic Ocean, about 400 miles off the Virgina shore and will not be recovered.
You can watch the launch live on NASA Ustream beginning at 10 p.m. on launch day at: http://www.ustream.com/channel/nasa-wallops
I will be onsite at Wallops for Universe Today.
And don’t forget to “Send Your Name to Mars” aboard NASA’s MAVEN orbiter- details here. Deadline: July 1, 2013
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Learn more about Conjunctions, Mars, Curiosity, Opportunity, MAVEN, LADEE and NASA missions at Ken’s upcoming lecture presentations
June 4: “Send your Name to Mars on MAVEN” and “CIBER Astro Sat, LADEE Lunar & Antares Rocket Launches from Virginia”; Rodeway Inn, Chincoteague, VA, 8:30 PM
NASA’s CIBER payload will launch from a suborbital launch pad located directly behind this Antares rocket erected at Pad 0A at the NASA Wallops Flight Facility along the Eastern shore of Virginia. Only a few hundred feet of beach sand and a miniscule sea wall separate the Wallops Island pads from the Atlantic Ocean waves and Mother Nature.
Credit: Ken Kremer (kenkremer.com)
This combined graphic shows new, high-resolution GBT imaging (in box) of recently discovered hydrogen clouds between M31 (upper right) and M33 (bottom left). Credit: Bill Saxton, NRAO/AUI/NSF.
Score another point for the National Science Foundation’s Green Bank Telescope (GBT) at the National Radio Astronomy Observatory (NRAO) in Green Bank. They have opened our eyes – and ears – to previously undetected region of hydrogen gas clouds located in the area between the massive Andromeda and Triangulum galaxies. If researchers are correct, these dwarf galaxy-sized sectors of isolated gases may have originated from a huge store of heated, ionized gas… Gas which may be associated with elusive and invisible dark matter.
“We have known for some time that many seemingly empty stretches of the Universe contain vast but diffuse patches of hot, ionized hydrogen,” said Spencer Wolfe of West Virginia University in Morgantown. “Earlier observations of the area between M31 and M33 suggested the presence of colder, neutral hydrogen, but we couldn’t see any details to determine if it had a definitive structure or represented a new type of cosmic feature. Now, with high-resolution images from the GBT, we were able to detect discrete concentrations of neutral hydrogen emerging out of what was thought to be a mainly featureless field of gas.”
So how did astronomers detect the extremely faint signal which clued them to the presence of the gas pockets? Fortunately, our terrestrial radio telescopes are able to decipher the representative radio wavelength signals emitted by neutral atomic hydrogen. Even though it is commonplace in the Universe, it is still frail and not easy to observe. Researchers knew more than 10 years ago that these repositories of hydrogen might possibly exist in the empty space between M33 and M32, but the evidence was so slim that they couldn’t draw certain conclusions. They couldn’t “see” fine grained structure, nor could they positively identify where it came from and exactly what these accumulations meant. At best, their guess was it came from an interaction between the two galaxies and that gravitational pull formed a weak “bridge” between the two large galaxies.
The animation demonstrates the difference in resolution from the original Westerbork Radio Telescope data (Braun & Thilker, 2004) and the finer resolution imaging of GBT, which revealed the hydrogen clouds between M31 and M33. Bill Saxton, NRAO/AUI/NSF Credit: Bill Saxton, NRAO/AUI/NSF.
Just last year, the GBT observed the tell-tale fingerprint of hydrogen gas. It might be thin, but it is plentiful and it’s spread out between the galaxies. However, the observations didn’t stop there. More information was gathered and revealed the gas wasn’t just ethereal ribbons – but solid clumps. More than half of the gas was so conspicuously aggregated that they could even have passed themselves off as dwarf galaxies had they a population of stars. What’s more, the GBT also studied the proper motion of these gas pockets and found they were moving through space at roughly the same speed as the Andromeda and Triangulum galaxies.
“These observations suggest that they are independent entities and not the far-flung suburbs of either galaxy,” said Felix J. Lockman, an astronomer at the NRAO in Green Bank. “Their clustered orientation is equally compelling and may be the result of a filament of dark matter. The speculation is that a dark-matter filament, if it exists, could provide the gravitational scaffolding upon which clouds could condense from a surrounding field of hot gas.”
And where there is neutral hydrogen gas, there is fuel for new stars. Astronomers also recognize these new formations could eventually be drawn into M31 and M33, eliciting stellar creation. To add even more interest, these cold, dark regions which exist between galaxies contain a large amount of “unaccounted-for normal matter” – perhaps a clue to dark matter riddle and the reason behind the amount of hydrogen yet to revealed in universal structure.
“The region we have studied is only a fraction of the area around M31 reported to have diffuse hydrogen gas,” said D.J. Pisano of West Virginia University. “The clouds observed here may be just the tip of a larger population out there waiting to be discovered.”
The international Super Cryogenic Dark Matter Search (SuperCDMS) has detected what may be the particle that's thought to make up dark matter throughout the Universe.
Dark matter: it’s invisible, it’s elusive, it’s controversial… and it’s everywhere — in the Universe, yes, but especially in the world of astrophysics, where researchers have been exhaustively trying to reveal its true identity for decades.
Now, scientists with the international Super Cryogenic Dark Matter Search (SuperCDMS) experiment are reporting the detection of a particle that’s thought to make up dark matter: a weakly-interacting massive particle, or WIMP. According to a press release from Texas A&M University (whose high-energy physicist Rupak Mahapatra is a principal investigator in the experiment) SuperCDMS has identified a WIMP-like signal at the 3-sigma level, which indicates a 99.8 percent chance of an actual discovery — a “concrete hint,” as it’s being called.
“In high-energy physics, a discovery is only claimed at 5-sigma or better,” Mahapatra said. “So this is certainly very exciting, but not fully convincing by the standards. We just need more data to be sure. For now, we have to live with this tantalizing hint of one of the biggest puzzles of our time.”
If this is indeed a WIMP it will be the first time such a particle has been directly observed, lending more insight into what dark matter is… or isn’t.
Notoriously elusive, WIMPs rarely interact with normal matter and therefore are difficult to detect. Scientists believe they occasionally bounce off, or scatter like billiard balls from, atomic nuclei, leaving behind a small amount of energy capable of being tracked by detectors deep underground, particle colliders such as the Large Hadron Collider at CERN and even instruments in space like the Alpha Magnetic Spectrometer (AMS) mounted on the International Space Station.
A stack of crystal germanium CDMS detectors (Fermilab)
The CDMS experiment, located a half-mile underground at the Soudan mine in northern Minnesota and managed by the United States Department of Energy’s Fermi National Accelerator Laboratory, has been searching for dark matter since 2003. The experiment uses very sophisticated detector technology and advanced analysis techniques to enable cryogenically cooled (almost absolute zero temperature at -460 degrees F) germanium and silicon targets to search for the rare recoil of dark matter particles.
This newly-announced detection actually comes from data acquired during an earlier phase of the experiment.
“This result is from data taken a few years ago using silicon detectors manufactured at Stanford that are now defunct,” Mahapatra said. “Increased interest in the low mass WIMP region motivated us to complete the analysis of the silicon-detector exposure, which is less sensitive than germanium for WIMP masses above 15 giga-electronvolts [one GeVa is equal to a billion electron volts] but more sensitive for lower masses. The analysis resulted in three events, and the estimated background is 0.7 events.”
Although Mahapatra says the result is certainly encouraging and worthy of further investigation, he cautions it should not be considered a discovery just yet.
“We are only 99.8 percent sure, and we want to be 99.9999 percent sure,” Mahapatra said. “At 3-sigma, you have a hint of something. At 4-sigma, you have evidence. At 5-sigma, you have a discovery.”
“In medicine, you can say you are curing 99.8 percent of the cases, and that’s OK. When you say you’ve made a fundamental discovery in high-energy physics, you can’t be wrong.”
– Dr. Rupak Mahapatra, SuperCDMS principal investigator, Texas A&M University
Advanced 6-inch silicon detectors developed by Mahapatra’s lab at Texas A&M
The collaboration will continue to probe this WIMP sector using the SuperCDMS Soudan experiment’s operating germanium detectors and is considering using larger, more advanced 6-inch silicon detectors developed at the Texas A&M’s Department of Electrical Engineering in future experiments.
The team has detailed its results in a paper published in arXiv that eventually will appear in Physical Review Letters. Mahapatra will also announce the results today at 12 p.m. CDT in a talk at the Mitchell Institute for Fundamental Physics and Astronomy.
From its vantage point about 400 km above Earth on the International Space Station, the Alpha Magnetic Spectrometer collects data from primordial cosmic rays from space. Credit: NASA
The first results from the largest and most complex scientific instrument on board the International Space Station has provided tantalizing hints of nature’s best-kept particle secrets, but a definitive signal for dark matter remains elusive. While the AMS has spotted millions of particles of antimatter – with an anomalous spike in positrons — the researchers can’t yet rule out other explanations, such as nearby pulsars.
“These observations show the existence of new physical phenomena,” said AMS principal investigator Samuel Ting,” and whether from a particle physics or astrophysical origin requires more data. Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”
The positron fraction measured by AMS. Credit: CERN.
The AMS was brought to the ISS in 2011 during the final flight of space shuttle Endeavour, the penultimate shuttle flight. The $2 billion experiment examines ten thousand cosmic-ray hits every minute, searching for clues into the fundamental nature of matter.
During the first 18 months of operation, the AMS collected of 25 billion events. It found an anomalous excess of positrons in the cosmic ray flux — 6.8 million are electrons or their antimatter counterpart, positrons.
The AMS found the ratio of positrons to electrons goes up at energies between 10 and 350 gigaelectronvolts, but Ting and his team said the rise is not sharp enough to conclusively attribute it to dark matter collisions. But they also found that the signal looks the same across all space, which would be expected if the signal was due to dark matter – the mysterious stuff that is thought to hold galaxies together and give the Universe its structure.
Additionally, the energies of these positrons suggest they might have been created when particles of dark matter collided and destroyed each other.
A screenshot from Ting’s presentation at CERN on April 3, 2013. ‘It took us 18 years to complete this result,’ Ting said.
The AMS results are consistent with the findings of previous telescopes, like the Fermi and PAMELA gamma-ray instruments, which also saw a similar rise, but Ting said the AMS results are more precise.
The results released today do not include the last 3 months of data, which have not yet been processed.
“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” Ting said.
Cosmic rays are charged high-energy particles that permeate space. An excess of antimatter within the cosmic ray flux was first observed around two decades ago. The origin of the excess, however, remains unexplained. One possibility, predicted by a theory known as supersymmetry, is that positrons could be produced when two particles of dark matter collide and annihilate. Ting said that over the coming years, AMS will further refine the measurement’s precision, and clarify the behavior of the positron fraction at energies above 250 GeV.
Although having the AMS in space and away from Earth’s atmosphere – allowing the instruments to receive a constant barrage of high-energy particles — during the press briefing, Ting explained the difficulties of operating the AMS in space. “You can’t send a student to go out and fix it,” he quipped, but also added that the ISS’s solar arrays and the departure and arrival of the various spacecraft can have an effect on thermal fluctuations the sensitive equipment might detect. “You need to monitor and correct the data constantly or you are not getting accurate results,” he said.
Despite recording over 30 billion cosmic rays since AMS-2 was installed on the International Space Station in 2011, the Ting said the findings released today are based on only 10% of the readings the instrument will deliver over its lifetime.
Asked how much time he needs to explore the anomalous readings, Ting just said, “Slowly.” However, Ting will reportedly provide an update in July at the International Cosmic Ray Conference.
This illustration shows the disk of our Milky Way galaxy, surrounded by a faint, extended halo of old stars. Astronomers using the Hubble Space Telescope to observe the nearby Andromeda galaxy serendipitously identified a dozen foreground stars in the Milky Way halo. They measured the first sideways motions (represented by the arrows) for such distant halo stars. The motions indicate the possible presence of a shell in the halo, which may have formed from the accretion of a dwarf galaxy. This observation supports the view that the Milky Way has undergone continuing growth and evolution over its lifetime by consuming smaller galaxies.
Illustration Credit: NASA, ESA, and A. Feild (STScI)
Like tantalizing tidbits stored in the vast recesses of one’s refrigerator, astronomers using NASA’s Hubble Space Telescope have evidence of a shell of stars left over from one of the Milky Way’s meals. In a study which will appear in an upcoming issue of the Astrophysical Journal researchers have revealed a group of stars moving sideways – a motion which points to the fact our galaxy may have consumed another during its evolution.
“Hubble’s unique capabilities are allowing astronomers to uncover clues to the galaxy’s remote past. The more distant regions of the galaxy have evolved more slowly than the inner sections. Objects in the outer regions still bear the signatures of events that happened long ago,” said Roeland van der Marel of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.
As curious as this shell of stars is, they offer even more information by revealing a chance to study the mysterious hidden mass of Milky Way – dark matter. With more than a hundred billion galaxies spread over the Universe, what better place to get a closer look than right here at home? The team of astronomers led by Alis Deason of the University of California, Santa Cruz, and van der Marel studied the outer halo, a region roughly 80,000 light years from our galaxy’s center, and identified 13 stars which may have come to light at the very beginning of the Milky Way’s formation.
What’s so special about this group of geriatric suns? In this case, it’s their movement. Instead of cruising along in a radial orbit, these elderly stars show tangential motion – an unexpected observation. Normally halo stars travel towards the galactic center, only to return outwards again. What could cause this double handful of stars to move differently? The research team speculates there could be an “over-density” of stars at the 80,000 light year mark.
As intriguing as these stars are, this strange shell was discovered somewhat by accident. Deason and her team winnowed out the outer halo stars from a seven year study of archival images taken by the Hubble telescope of the Andromeda galaxy. While looking some twenty times further away at our neighboring galaxy’s stars, these strange moving stars came to light as foreground objects… objects that “cluttered” the images. While these halo stars were bad for that particular study, they were very good for Deason and the team. It gave them the chance to take a really close look at the motion of the Milky Way’s halo stars.
However, seeing these stars wasn’t easy. Thanks to Hubble’s incredible resolution and light gathering power, each image contained more than 100,000 individual stars. “We had to somehow find those few stars that actually belonged to the Milky Way halo,” van der Marel said. “It was like finding needles in a haystack.”
So how did the astronomers separate the shell stars from those that belonged to the outer fringes of the Andromeda? The initial observations picked the stars out based on their color, brightness and sideways motion. Thanks to parallax, our halo stars seem to move far faster simply because they are closer. Through the work of team member Tony Sohn of STSci, these revolutionary stars were identified and measured. Their tangential motion was observed and recorded with five percent precision. Not a speedy process when you consider these shell stars only move across the sky at a rate of about one milliarcsecond per year!
“Measurements of this accuracy are enabled by a combination of Hubble’s sharp view, the many years’ worth of observations, and the telescope’s stability. Hubble is located in the space environment, and it’s free of gravity, wind, atmosphere, and seismic perturbations,” van der Marel said.
What makes the team so confident in their findings? As we know, stars at home in our galaxy’s inner halo have highly radial orbits. When a comparison was made between the sideways motion of the outer halo stars with the inner motions, the researchers found equality. According to computer simulations of galaxy formation, outer stars should continue to have radial motion as they move outward into the halo, but these new findings prove opposite. What could cause it? A natural explanation would be an accretion event involving a satellite galaxy.
To further substantiate their findings, the team compared their results with data taken by the Sloan Digital Sky Survey involving halo stars. It was a eureka moment. The observations taken by the SDSS revealed a higher density of stars at roughly the same distance as the shell-shocked travelers. And the Milky Way isn’t alone. Other studies of halo stars involved in both the Triangulum and Andromeda show a large number of halo stars existing to a certain point – only to drop off. Deason realized this wasn’t just a weird coincidence. “What may be happening is that the stars are moving quite slowly because they are at the apocenter, the farthest point in their orbit about the hub of our Milky Way,” Deason explained. “The slowdown creates a pileup of stars as they loop around in their path and travel back towards the galaxy. So their in and out or radial motion decreases compared with their sideways or tangential motion.”
As exciting as these findings are, they aren’t news. Shell stars have been observed in the halos of other galaxies and were predicted to be part of the Milky Way. By nature, they should have been there – but they were simply to dim and too far-flung to make astronomers positive of their presence. Not any more. Now that astronomers know what to look for, they are even more anxious to dig into Hubble’s archives. “These unexpected results fuel our interest in looking for more stars to confirm that this is really happening,” Deason said. “At the moment we have quite a small sample. So we really can make it a lot more robust with getting more fields with Hubble.” The Andromeda observations only cover a very small “keyhole view” of the sky.
So what’s next? Now the team can paint an even more fine portrait of the Milky Way’s evolutionary history. By understanding the motions and orbits of the “shell” of stars in the halo, they might even by able to give us a accurate mass. “Until now, what we have been missing is the stars’ tangential motion, which is a key component. The tangential motion will allow us to better measure the total mass distribution of the galaxy, which is dominated by dark matter. By studying the mass distribution, we can see whether it follows the same distribution as predicted in theories of structure formation,” Deason said.
Hubble mosaic of massive galaxy cluster MACS J0717.5+3745, thought to be connected by a filament of dark matter. Credit: NASA, ESA, Harald Ebeling (University of Hawaii at Manoa) & Jean-Paul Kneib (LAM)
Even though teams of scientists around the world are at this very moment hot on the trail of dark matter — the “other stuff” that the Universe is made of and supposedly accounts for nearly 80% of the mass that we can’t directly observe (yet) — and trying to quantify exactly how so-called “dark energy” drives its ever-accelerating expansion, perhaps one answer to these ongoing mysteries is maybe they don’t exist at all.
This is precisely what one astronomer is suggesting in a recent paper, submitted Dec. 3 to Astrophysical Journal Letters.
In a paper titled “An expanding universe without dark matter and dark energy” (arXiv:1212.1110) Pierre Magain, a professor at Belgium’s Institut d’Astrophysique et de Géophysique, proposes that the expansion of the Universe could be explained without the need for enigmatic material and energy that, to date, has yet to be directly measured.
In addition, Magain’s proposal puts a higher age to the Universe than what’s currently accepted. With a model that shows a slower expansion rate during the early Universe than today, Magain’s calculations estimate its age to be closer to 15.4 – 16.5 billion years old, adding a couple billion more candles to the cosmic birthday cake.
The benefit to a slightly older Universe, Magain posits, is that it’s not so uncannily close to the apparent age of the most distant galaxies recently found — such as MACS0647-JD, which is 13.3 billion light-years away and thus (based on current estimates, see graphic at right) must have formed when the Universe was a mere 420 million years old.
Using accepted physics of how time behaves based on Einstein’s theory of general relativity — namely, how the passage of time is relative to the position and velocity of the viewer (as well as the intensity of the gravitational field the viewer is within) — Magain’s model allows for an observer located within the Universe to potentially be experiencing a different rate of time than a hypothetical viewer located outside the Universe. Not to be so metaphysical as to presume that there are external observers of our Universe but merely to say that an external point would be a fixed one against which one could benchmark a varying passage of time inside the Universe, Magain calls this universal relativity.
A viewer experiencing universal relativity would, Magain claims, always measure the curvature of the Universe to be equal to zero. This is what’s currently observed, a “flatness problem” that Magain insinuates is strangely coincidental.
By attributing an expanding Universe to dark energy and the high velocities of stars along the edges of galaxies (as well as the motions of galaxy clusters themselves) to dark matter, we may be introducing ad hoc elements to the Universe, says Magain. Instead, he proposes his “more economical” model — which uses universal relativity — explains these apparently accelerating, increasingly expanding behaviors… and gives a bigger margin of time between the Big Bang and the formation of the first galactic structures.
There’s quite a bit of math involved, and since I never claimed to understand physics equations you can check out the original paper here.
While intriguing, the bottom line is that dark energy and dark matter have still managed to elude science, existing just outside the borders of what can be observed (although the gravitational lensing effects of what’s thought to be dark matter filaments have been observed by Hubble) and Magain’s paper is merely putting another idea onto the table — one that, while he recognizes needs further testing and relies upon very specific singular parameters, doesn’t depend upon invisible, unobservable and mysteriously dark “stuff”. Whether it belongs on the table or not will be up to other astrophysicists to decide.
Prof. Magain’s research was supported by ESA and the Belgian Science Policy Office.
At right: Artist’s impression of dark matter (h/t to Steve Nerlich)
Note: this is “just” a submitted paper and has not been selected for publication yet. Any hypotheses proposed are those of the author and are not endorsed by this site. (Personally I like dark matter. It’s fascinating stuff… even if we can’t see it. Want an astrophysicist’s viewpoint on the existence of dark matter? Check out Ethan Siegel’s blog response here.)
The image on the left shows a portion of our sky, called the Boötes field, in infrared light, while the image on the right shows a mysterious, background infrared glow captured by NASA’s Spitzer Space Telescope in the same region of sky.Credit: NASA/JPL-Caltech
What causes the mysterious glow of radiation seen across the entire sky by infrared telescopes? The answer may lie in a combination of concepts that are relatively new to the field of astronomy, and are somewhat controversial, too. Rogue stars that have been kicked out of galaxies may be embedded in dark matter halos that have been theorized to surround galaxies. While these dark matter halos have previously only been detected indirectly by observing their gravitational effects, they may also hold the source of the enigmatic background glow of radiation.
“The infrared background glow in our sky has been a huge mystery,” said Asantha Cooray of the University of California at Irvine, lead author of the new research published today in the journal Nature. “We have new evidence this light is from the stars that linger between galaxies. Individually, the stars are too faint to be seen, but we think we are seeing their collective glow.”
The collective glow is from the “interhalo” of dark matter halos that pervade the Universe, and may answer the big question of why the amount of light observed exceeds the amount of light emitted from known galaxies.
“Galaxies exist in dark matter halos that are much bigger than the galaxies; when galaxies form and merge together, the dark matter halo gets larger and the stars and gas sink to the middle of the halo,” said Edward L. (Ned) Wright from UCLA and a member of the team that used the Spitzer Space Telescope to seek out the source of the infrared light. “What we’re saying is one star in a thousand does not do that and instead gets distributed like dark matter. You can’t see the dark matter very well, but we are proposing that it actually has a few stars in it — only one-tenth of 1 percent of the number of stars in the bright part of the galaxy. One star in a thousand gets stripped out of the visible galaxy and gets distributed like the dark matter.”
The dark matter halo is not totally dark, Wright said. “A tiny fraction, one-tenth of a percent, of the stars in the central galaxy has been spread out into the halo, and this can produce the fluctuations that we see.”
In large clusters of galaxies, astronomers have found much higher percentages of intra-halo light, as large as 20 percent, Wright said.
For this study, Cooray, Wright and colleagues used the Spitzer Space Telescope to produce an infrared map of a region of the sky in the constellation Boötes. The light has been travelling to us for 10 billion years.
“Presumably this light in halos occurs everywhere in the sky and just has not been measured anywhere else,” said Wright, who is also principal investigator of NASA’s Wide-field Infrared Survey Explorer (WISE) mission.
“If we can really understand the origin of the infrared background, we can understand when all of the light in the universe was produced and how much was produced,” Wright said. “The history of all the production of light in the universe is encoded in this background. We’re saying the fluctuations can be produced by the fuzzy edges of galaxies that existed at the same time that most of the stars were created, about 10 billion years ago.”
The light appears at a blotchy pattern in the Spitzer images.
The new finding are at odds with a study that came out this summer. Alexander “Sasha” Kashlinsky of NASA’s Goddard Space Flight Center and his team looked at this same patch of sky with Spitzer and proposed the light making the unusual pattern was coming from the very first stars and galaxies.
In the new study, Cooray and colleagues looked at data from a larger portion of the sky, called the Bootes field, covering an arc equivalent to 50 full Earth moons. These observations were not as sensitive as those from the Kashlinsky group’s studies, but the larger scale allowed researchers to analyze better the pattern of the background infrared light.
“We looked at the Bootes field with Spitzer for 250 hours,” said co-author Daniel Stern of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Studying the faint infrared background was one of the core goals of our survey, and we carefully designed the observations in order to directly address the important, challenging question of what causes the background glow.”
The team concluded the light pattern of the infrared glow is not consistent with theories and computer simulations of the first stars and galaxies. Researchers say the glow is too bright to be from the first galaxies, which are thought not to have been as large or as numerous as the galaxies we see around us today. Instead, the scientists propose a new theory to explain the blotchy light, based on theories of “intracluster” or “intrahalo” starlight.
The team said more research is needed to confirm these findings, adding that the James Webb Space Telescope should help.
“The keen infrared vision of the James Webb Telescope will be able to see some of the earliest stars and galaxies directly, as well as the stray stars lurking between the outskirts of nearby galaxies,” said Eric Smith, JWST’s deputy program manager at NASA Headquarters in Washington. “The mystery objects making up the background infrared light may finally be exposed.”
Hubble’s view of massive galaxy cluster MACS J0717.5+3745. The large field of view is a combination of 18 separate Hubble images. Credit:
NASA, ESA, Harald Ebeling (University of Hawaii at Manoa) & Jean-Paul Kneib (LAM)
Earlier this year, astronomers using the Hubble Space Telescope were able to identify a slim filament of dark matter that appeared to be binding a pair of distant galaxies together. Now, another filament has been found, and scientists a have been able to produce a 3-D view of the filament, the first time ever that the difficult-to-detect dark matter has been able to be measured in such detail. Their results suggest the filament has a high mass and, the researchers say, that if these measurements are representative of the rest of the Universe, then these structures may contain more than half of all the mass in the Universe.
Dark matter is thought to have been part of the Universe from the very beginning, a leftover from the Big Bang that created the backbone for the large-scale structure of the Universe.
“Filaments of the cosmic web are hugely extended and very diffuse, which makes them extremely difficult to detect, let alone study in 3D,” said Mathilde Jauzac, from Laboratoire d’Astrophysique de Marseille in France and University of KwaZulu-Natal, in South Africa, lead author of the study.
The team combined high resolution images of the region around the massive galaxy cluster MACS J0717.5+3745 (or MACS J0717 for short) – one of the most massive galaxy clusters known — and found the filament extends about 60 million light-years out from the cluster.
The team said their observations provide the first direct glimpse of the shape of the scaffolding that gives the Universe its structure. They used Hubble, NAOJ’s Subaru Telescope and the Canada-France-Hawaii Telescope, with spectroscopic data on the galaxies within it from the WM Keck Observatory and the Gemini Observatory. Analyzing these observations together gives a complete view of the shape of the filament as it extends out from the galaxy cluster almost along our line of sight.
The team detailed their “recipe” for studying the vast but diffuse filament. .
First ingredient: A promising target. Theories of cosmic evolution suggest that galaxy clusters form where filaments of the cosmic web meet, with the filaments slowly funnelling matter into the clusters. “From our earlier work on MACS J0717, we knew that this cluster is actively growing, and thus a prime target for a detailed study of the cosmic web,” explains co-author Harald Ebeling (University of Hawaii at Manoa, USA), who led the team that discovered MACS J0717 almost a decade ago.
Second ingredient: Advanced gravitational lensing techniques. Albert Einstein’s famous theory of general relativity says that the path of light is bent when it passes through or near objects with a large mass. Filaments of the cosmic web are largely made up of dark matter [2] which cannot be seen directly, but their mass is enough to bend the light and distort the images of galaxies in the background, in a process called gravitational lensing. The team has developed new tools to convert the image distortions into a mass map.
Third ingredient: High resolution images. Gravitational lensing is a subtle phenomenon, and studying it needs detailed images. Hubble observations let the team study the precise deformation in the shapes of numerous lensed galaxies. This in turn reveals where the hidden dark matter filament is located. “The challenge,” explains co-author Jean-Paul Kneib (LAM, France), “was to find a model of the cluster’s shape which fitted all the lensing features that we observed.”
Finally: Measurements of distances and motions. Hubble’s observations of the cluster give the best two-dimensional map yet of a filament, but to see its shape in 3D required additional observations. Colour images [3], as well as galaxy velocities measured with spectrometers [4], using data from the Subaru, CFHT, WM Keck, and Gemini North telescopes (all on Mauna Kea, Hawaii), allowed the team to locate thousands of galaxies within the filament and to detect the motions of many of them.
A model that combined positional and velocity information for all these galaxies was constructed and this then revealed the 3D shape and orientation of the filamentary structure. As a result, the team was able to measure the true properties of this elusive filamentary structure without the uncertainties and biases that come from projecting the structure onto two dimensions, as is common in such analyses.
The results obtained push the limits of predictions made by theoretical work and numerical simulations of the cosmic web. With a length of at least 60 million light-years, the MACS J0717 filament is extreme even on astronomical scales. And if its mass content as measured by the team can be taken to be representative of filaments near giant clusters, then these diffuse links between the nodes of the cosmic web may contain even more mass (in the form of dark matter) than theorists predicted.
