Dark Matter's New Wrinkle: It May Behave Like Wavy Fluid

The mysterious dark matter that makes up most of the matter in the universe may behave more like wavy fluids than solid particles, helping to explain the shapes of galaxies, a new study suggests.

Dark matter is one of the greatest mysteries in the cosmos. It is thought to be an invisible and mostly intangible substance that makes up five-sixths of all matter in the universe.

The scientific consensus is that dark matter is composed of a new type of particle, one that interacts very weakly with all the known forces of the universe and is mostly only detectable via the gravitational pull it exerts. However, what kind of particle dark matter consists of remains unknown. 

There are two known types of particles in the universe, fermions and bosons. Fermions include particles such as protons, neutrons and electrons, while bosons include particles such as the photons that make up light.

The mainstream focus for dark matter has been on massive fermions, said study co-author Tom Broadhurst, a cosmologist at the University of the Basque Country in Spain. However, so far these fermion candidates for dark matter have not been generated by the Large Hadron Collider  (LHC), the most powerful particle accelerator on Earth, nor have any been confirmed by the Large Underground Xenon (LUX) experiment, the most sensitive dark-matter detector ever built.

As a result, some researchers have suggested that dark matter might not be made of extremely high-mass heavy fermions, but low-mass light bosons instead. For instance, Broadhurst and his colleagues investigated the behavior of a boson with a mass of less than 10^-22 electron-volts, or less than a tenth of a billionth of a billionth of billionth the mass of an electron.

The difference between fermions and bosons is that a fermion cannot occupy the same state at the same time as another fermion. As an analogy, a state is like a seat, and two or more fermions cannot sit in the same seat simultaneously. In contrast, two or more bosons can occupy the same state at the same time, and can therefore clump into so-called Bose-Einstein condensates that act like single blobs.

Now, Broadhurst and his colleagues have for the first time simulated what galaxies might look like if dark matter was made of light bosons. They said their models more accurately reflect what galaxies actually look like than more conventional models where dark matter is made of fermions.

The researchers investigated dwarf spheroidal galaxies, the smallest and most common class of galaxy, which have centers with masses equal to about 10 million suns. The basic properties of dwarf spheroidal galaxies are very difficult to explain with simulations in which dark matter is made of heavy fermions; these models suggest that much smaller galaxies should exist than what astronomers see, and that dark matter in dwarf spheroidal galaxies should be much less smoothly distributed than what is observed.

Broadhurst and his colleagues simulated the way the gravitational pull of dark matter Bose-Einstein condensates influences the evolution of galaxies. They found these simulated blobs of dark matter led to galaxies that better matched the ones that astronomers see.

The scientists found these dark matter Bose-Einstein condensates are full of waves. Stable waves known as soliton waves are expected in the middle of galaxies, "surrounded by extended lumpy halos of dark matter comprised of giant quantum density fluctuations that fluctuate over time," Broadhurst said. This behavior can help explain both the size of the dwarf spheroidal galaxies seen and why dark matter is distributed relatively smoothly within them.

Another consequence of dark matter Bose-Einstein condensates is that galaxy formation should have begun about 330 million years after the Big Bang. This is substantially delayed compared to models that envision dark matter being made of fermions, which suggest that galaxy formation should have begun about 50 million years after the Big Bang. Future observations by NASA's Hubble Space Telescope could help determine whether dark matter consists of fermions or bosons, study team members said.

Broadhurst and his colleagues Hsi-Yu Schive and Tzihong Chiueh detailed their findings in June in the journal Nature Physics.

Orion on the Pad: NASA Rolls Out Space Capsule for 1st Test Flight

CAPE CANAVERAL, Fla. — NASA's first space-bound Orion capsule has arrived at the launch pad, where it will lift off in early December on an uncrewed test flight in support of NASA's plans for future astronaut missions beyond Earth orbit.

The gumdrop-shaped spacecraft, encased within a white aerodynamic shell and topped by a launch escape tower, rolled up to the base of Space Launch Complex 37B at the Cape Canaveral Air Force Station in Florida.

The capsule, which is set to embark on Dec. 4 on NASA's Exploration Flight Test-1 (EFT-1), rode out to the pad atop a multi-wheeled transporter. A banner hung on the front of the vehicle read, "Neil Armstrong Operations & Checkout Building 'I'm On Board,'" referencing the building where the spacecraft was assembled. 

"I gotta tell you, this is special," Bob Cabana, the director of NASA's Kennedy Space Center and a former astronaut, told reporters during a press conference on Monday . "This is our first step on the journey to Mars."

"To see the vehicle on top of the service module with the launch abort system attached, it is quite a stack," Cabana continued. "And it is going to look really good on top of the Delta IV [rocket]."

The Orion's journey to the pad began on Tuesday night at 8:54 p.m. EST) at a hangar some 22 miles (35 kilometers) away at the Kennedy Space Center.

"To see the actual vehicle, the first [Orion] that is going to fly, is an amazing sight," Rex Walheim, a NASA astronaut who flew onboard the final space shuttle mission and now represents the astronaut office in the Orion program, told collectSPACE. "It just looks beautiful and it is just so nice seeing us get a new vehicle to the launch pad."

The six-hour rollout originated at the Launch Abort System Facility, where the Orion spacecraft was equipped with its escape system tower and enveloped within its outer shell "ogive" panels.

The Exploration Flight Test-1 mission will see the in-flight separation of these components from the Orion as part of the mission's test objectives.

"EFT-1 is basically a compilation of what I would say are the riskiest events we're going to see when we fly people," Mark Geyer, NASA's Orion program manager, said during a press conference held Thursday (Nov. 6). "So this test flight is a great opportunity for us to fly those and actually see them in operation."

"Some of these [mission] events are very difficult or even impossible to test on the ground, so it is important that we fly them," Geyer continued. "EFT-1 gives us a chance to put all those together in a test flight."

On the way out to SLC-37B, the Orion paused in front of the 52-story-tall Vehicle Assembly Building, where NASA plans to assemble its Space Launch System rockets that will fly Orion on future missions out to the vicinity of the moon and eventually to Mars. The capsule also rolled past Pad 39B, where the space agency's Saturn V moon-bound rockets and space shuttles left Earth, and from where the SLS will launch.

Now at its departure site, the 72-foot-tall (22-meter) Orion, complete with its booster adapter section, will be hoisted 170 feet (52 meters) into the air and mounted to the United Launch Alliance Delta IV Heavy rocket that will launch it into Earth orbit. The EFT-1 mission is scheduled to lift off , just after sunrise.

The flight test will take the Orion 15 times farther out into space than the International Space Station on a four-and-a-half-hour mission to test many of the systems critical for human missions into deep space. After circling the planet twice, the Orion will reenter Earth's atmosphere at 20,000 miles per hour before descending under parachutes to a splashdown in the Pacific Ocean.

Google Leases NASA's Moffett Field, Historic Hangar for $1.2 Billion

A Google subsidiary will lease a NASA facility in California's Bay Area for $1.16 billion over the next 60 years, agency officials announced Monday (Nov. 10).

Planetary Ventures, LLC will lease Moffett Federal Airfield (MFA), which is currently managed by NASA's Ames Research Center, and restore the facility's historic Hangar One, a huge building that has been a Silicon Valley landmark since the 1930s.

"As NASA expands its presence in space, we are making strides to reduce our footprint here on Earth," NASA Administrator Charles Bolden said in a statement. "We want to invest taxpayer resources in scientific discovery, technology development and space exploration — not in maintaining infrastructure we no longer need. Moffett Field plays an important role in the Bay Area and is poised to continue to do so through this lease arrangement."

The agreement should save NASA $6.3 million per year in operations costs on top of the lease value, agency officials said.

Planetary Ventures will invest more than $200 million in the 1,000-acre (405 hectares) property, which also includes Hangar Two and Hangar Three, two runways, a flight-operations building, and a private golf course.

The company will refurbish all three hangars and use them as research facilities in an attempt to develop new technologies in space exploration, robotics and other high-tech fields, NASA officials said. Planetary Ventures will also establish a facility on the site that will teach the public about MFA's historical significance.

"We look forward to rolling up our sleeves to restore the remarkable landmark Hangar One, which for years has been considered one of the most endangered historic sites in the United States," said David Radcliffe, Vice President of Real Estate and Workplace Services at Google.

Ames is NASA's lead center for supercomputing and has helmed a number of important missions over the years, including the planet-hunting Kepler space telescope and the Lunar Atmosphere and Dust Environment Explorer (LADEE) probe, which studied the moon's wispy atmosphere after launching in September 2013.

'Muscles' Triggered by Electricity Could Power Tiny Robots

Tiny electrically activated "muscles" could one day give rise to microscopic robots that are smaller than a grain of sand, researchers say.

The chains of particles that make up these muscles could also lead to electronics that can automatically rewire themselves as desired, scientists added.

Microscopic robots, or microbots, could one day swim inside the body to fight disease or crawl into bombs to defuse them, among many other applications. "They could work together and go places that have never been possible before," said study co-author Michael Solomon, a chemical engineer at the University of Michigan at Ann Arbor.

However, building these robots and making them mobile remain two major challenges. "If you imagine a microscale robot in the future, it would need ways to move autonomously and it would need to be able to exert forces, by pushing or pulling on other objects," Solomon said.

Now, researchers suggest muscles created from self-assembling chains of microscopic particles could help power microbots in the future. The scientists detailed their findings online today (Nov. 10) in the journal Nature Materials.

The researchers started with spherical particles made up of a combination of polystyrene, the plastic material used in Styrofoam. They stretched these particles in a machine until they were the shape of rice grains, about 0.6 microns wide and 3 microns long. (In comparison, the average width of a human hair is about 100 microns.)

The scientists coated one side of each particle with gold. A particle with two different faces is known as a Janus particle, named after the two-faced Roman god Janus.

The gilded halves of the Janus particles attracted each other in salty water — the more salt in the water, the stronger the attraction. The ideal concentration of salt was about half that found in the sports drink Powerade, the researchers said.

On their own, the particles formed short chains of overlapping pairs, averaging about 50 to 60 particles per chain. However, when exposed to an alternating electric current, the chains elongated, seeming to add new particles indefinitely.

By expanding and contracting, these fibers could work like little muscles, said study co-author Sharon Glotzer, a computational physicist and chemical engineer at the University of Michigan at Ann Arbor. "We have extended and retracted them many times," Solomon said. "The degree of control we have over the chains is exciting."

"The findings point the way toward a new class of reconfigurable materials made of micron-size particles — materials that can be triggered to morph and change shape in response to changes in environment or on demand," Glotzer told Live Science.

The scientists found that gold plating and alternating electric current could make the chains extend by about 36 percent.

"The gold-gold bond between particles that stabilizes the chains is very strong — it would be very hard to pull the chains apart if they were gripped from the side," Solomon told Live Science. "However, the force required for the particles to slip past each other along the chain is not as great. The alternating-current field provides enough force for the particles to slide past each other, locking them into a new, extended configuration."

Although the force generated by the fibers is about 1,000 times weaker than human muscle tissue per unit area, it may be enough for microbots. "The next step is to organize groups of these chains into bundles," Solomon said. "If we can get the chains to swarm together, we can get them to lift loads, move around, do things that biological muscles do."

Microbots powered by muscles are likely many years away, but in the meantime, the Janus particles could lead to electronics that rewire themselves on demand, the researchers said.

"These chains are essentially wires, so you could assemble them into a circuit for reconfigurable electronics," Solomon said in a statement.