Several weeks ago, I wrote about a lively session at the AAAS Meeting about dark matter. At the meeting, Nobel laureate Samuel Ting hinted that he may have further evidence of the mysterious matter that makes up a quarter of the mass of our universe. He said the results would be published in a few weeks, and much to reporters dismay, left it at that.

Today, speaking from CERN, Ting finally announced the results. They will be published on Friday in the journal Physical Review Letters.

Ting spent several years (almost two decades!) convincing NASA and others to establish a detector in space to measure dark matter. Now, the Alpha Magnetic Spectrometer (AMS) experiment, installed on the International Space Station in 2011, studies cosmic rays before they have a chance to interact with the Earth’s atmosphere, and the secret to dark matter could lie in these cosmic rays.

Scientists believe that an excess of positrons in the cosmic ray flux could be the result of dark matter particles colliding and annihilating. One of the leading explanations for dark matter, a subset of particles collectively known as “weakly-interacting massive particles” (or “WIMPs”), would create positrons as a by-product of colliding with one another: individual collisions would happen rarely, but scattered throughout the Universe, they would result in a detectable bath of positrons of different energies. And AMS indeed detected an excess of these particles. While this has been measured in the past by other space-based observatories, the data from AMS represents the largest collection of positron particles recorded in space.

“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 remarked. “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.”

However promising the results, they may not signal dark matter at all. The positrons could originate from pulsars distributed around the galactic plane. Now AMS will further refine the measurement’s precision, and gather and analyze more data. Ting believes there’s no question that in the next year or two, we will understand exactly what these results indicate. It could be dark matter. Stay tuned…

Dark matter provided a lively topic of discussion at the recent AAAS Meeting in Boston. Michael Turner, of the University of Chicago’s Kavli Institute for Cosmological Physics, explained it this way at a press conference: “It’s something new. No particle in the standard model can account for it.” And he believes the discovery of the culprit particle is right around the corner; hence the decade of the WIMPs.

As Ryan Wyatt mentioned in his post last month from the AAS Meeting (such similar names, I know), both the Large Hadron Collider (LHC) and the Large Underground Xenon Experiment (LUX) are looking for these particles. In addition, a detector onboard the International Space Station, called the Alpha Magnetic Spectrometer (AMS), has joined the hunt. (Okay, I promise no more acronyms.)

The Alpha Magnetic Spectrometer is the brainchild of Nobel laureate Samuel Ting, who also presented at the press conference. It took Ting 16 years to get AMS into space; it’s now been collecting data for 18 months. And it sounds like they may already have results. Ting was vague, no matter how hard reporters tried to press him, but it sounds like his team plans to publish something in the next few weeks. With the length of time it took to make AMS a reality, Ting says, the results will certainly be worthwhile.

Here’s what he did clarify. AMS has seen 25 billion events—not many for a particle detector like the LHC, but quite a few for a space detector. Almost 8 billion of those are electrons and positrons, and scientists are working around the clock to understand how these interact with one another. Does the ratio between the two change over time? Turner explained that if scientists see a rise followed by dramatic fall, that will indicate a unique source—perhaps dark matter.

So now we must wait for the publication.  And remember, according to Turner’s timeline, we have a whole decade to make discoveries. Ting’s paper could take just a small step toward the description of dark matter. Lisa Randall, a theoretical physicist at Harvard, reminded us that a lot of stuff can mimic dark matter. So it could be a step in the wrong direction. But for her, how models of dark matter fit into these experiments of dark matter is all part of the process. “We’re learning more along the way.”

AMS particle detector: NASA

The third Thursday of every month, the Morrison Planetarium hosts “Universe Update” at the 6:30 planetarium show during NightLife. I select my favorite astronomy stories from the past month, and I give a brief run-down of current discoveries while taking audiences on a guided tour of the Universe. As you may or may not know, the planetarium sports a three-dimensional atlas of the Universe, so we can take you places virtually while talking about the latest astronomy news.

I always start at Earth and work my way out to cosmological distances, so I’ll list the news stories in the same order—from closest to farthest from home.

Fourth graders from the Emily Dickinson Elementary School in Bozeman, Montana, proved themselves more creative than NASA engineers! Crazy rocket scientists named their two lunar-orbiting spacecraft “GRAIL-A” and “GRAIL-B” (where, of course, “GRAIL” is an acronym, which stands for “Gravity Recovery and Interior Laboratory”). The elementary school students selected the names “Ebb” and “Flow,” which NASA selected as the winning contribution in a nationwide contest. The GRAIL mission measures the ebb and flow of gravity, in a sense, as the two spacecraft orbit the Moon and measure variations in its gravitational pull. From the GRAIL website:

As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the Moon’s gravitational field.

A little farther from home, new reports from a comet impact on the Sun that took place last July. We like to describe comets as “dirty snowballs,” and as you might imagine, a comet getting too close to the Sun stands a snow ball’s chance in… Well, a million-degree plasma irradiated by incident solar flux. The comet evaporated over a period of about 20 minutes, and as described in a paper that appears in today’s Science magazine, it probably measured between 150 and 300 feet across and had a mass equivalent to an aircraft carrier. According to Karel Schrijver, a solar scientist at Lockheed Martin in Palo Alto, the comet moved speedily to its demise: “It was moving along at almost 400 miles per second through the intense heat of the Sun—and was literally being evaporated away.”

A fair bit farther from the scorching heat of the Sun, the Dawn spacecraft is sending back gorgeous images of the asteroid Vesta, including this gorgeous snapshot of a crater on the asteroid’s surface. Dawn has entered a low-altitude orbit that gives it a close look at the potato-shaped planetoid. Learning more about such objects should help us better understand the formation of the solar system, and after its stay at Vesta, Dawn will move on to Ceres, the dwarf planet (like Pluto) that resides between the orbits of Mars and Jupiter.

Beyond our own solar system, of course, we are rapidly discovering planets in orbit around other stars: these extrasolar planets (or exoplanets) now number in excess of 700, and astronomers find more all the time.

As I described in one of my updates from the American Astronomical Society meeting last week, astronomers have announced the discovery of the most compact extrasolar planetary system yet detected. Looking at the KOI 961 system side-by-side with Jupiter and its major satellites strikes me as a particularly illuminating comparison: only 70% larger than Jupiter, the host star (the smallest known to have planets) has at least three planets (the smallest yet found) in orbit around it, the smallest of which is about the size of Mars. John Johnson, an astronomer at Caltech, announced the superlative system last week, and on April 2nd, he will give a talk in the Morrison Planetarium as part of our Benjamin Dean Lecture Series, “The Quest for Habitable Planets Orbiting Red Dwarfs.”

And astronomers have help in their search. Just this week, we had a glimpse into the democratization of astronomy… Viewers of a British television program(me) may have discovered a new exoplanet! Evidence from the Kepler mission suggests the existence of a Neptune-sized planet around the star SPH10066540, orbiting every 90 days at a distance equivalent to Mercury from our Sun. The discovery awaits confirmation, but you don’t have to watch telly in the U.K. to join in the search for such objects. You can go to the PlanetHunters website and start sifting through Kepler data in hopes of finding a planet of your own…

In another of my posts last week, I mentioned the spectacular new Spitzer image of Cygnus X, a massive star-forming region in the constellation (you guessed it) Cygnus. Ten times the size of the Orion Molecular Cloud Complex, Cygnus X appears to host some 26,000 possible young stellar objects, according to an announcement last week.

Moving farther from home, I talked a bit about the new dark matter map that I previously described in a post from Austin. It turns out that analyzing the light from 10 million galaxies call tell you a lot about where dark matter resides, and since dark matter drives the formation of much of the structure in the Universe, that knowledge helps us understand more about the evolution of the cosmos…

The dark matter maps tell one part of the story, but we also rely on studies of the cosmic microwave background to tease out how the Universe has evolved over time. Since 2003, the gold standard of such measurements have come from the Wilkinson Microwave Anisotropy Probe (WMAP). But ESA’s Planck mission recently completed its survey of the cosmic microwave background: the sensor used to make the observations ran out of its coolant a little less than a week ago. It had collected more than two years’ worth of data, however, and the first new high-resolution maps will be released early next year. (Hey! It takes a while to process all that data.)

That’s all for now. Check back for next month’s update! Or come to NightLife on Thursday, 15 February, and check out “Universe Update” live in the Morrison Planetarium.

Ryan Wyatt is the director of the Morrison Planetarium and Science Visualization at the California Academy of Sciences.

Image: SOHO (ESA & NASA)

In broad strokes…  We have dark energy, which makes up 73-74% of the Universe and causes the Universe to accelerate in its expansion. Dark matter, on the other hand, makes up 22-23% of the Universe, accounts for most of the mass and exerts gravitational effects on galaxies—influencing the rotational speed, orbital velocity, and distribution of the remaining 4% of the Universe, namely the stuff we can actually see.

But what if you could see the dark stuff? Would the images match up to the theories describing it?

Scientists at NASA/JPL, working with a West Point mathematician and using the Hubble Space Telescope, have created one of the sharpest maps to date of dark matter.

Focusing on a galaxy cluster called Abell 1689, 2.2 billion light years away, the team was able to create a map of dark matter using gravitational lensing.

Abell 1689 contains about 1,000 galaxies and trillions upon trillions of stars. Its gravitational influence, the majority of which results from dark matter, acts like a cosmic magnifying glass, bending and amplifying light from galaxies much farther away. This effect, called gravitational lensing, produces multiple, warped, and greatly magnified images of those galaxies, like the view in a funhouse mirror. By studying the distorted images, astronomers estimated the amount of dark matter within the cluster. If the cluster’s gravity only came from the visible galaxies, the lensing distortions would be much, much weaker.

Researchers used the observed positions of 135 “lensed” images of 42 background galaxies to calculate the location and amount of dark matter in the cluster. They superimposed a map of these inferred dark matter concentrations, tinted blue here, on a Hubble image of the cluster.

According to team leader Dan Coe, “the lensed images are like a big puzzle. Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions.”

The new dark matter observations may yield new insights into the role of dark energy in the Universe’s early formative years.

Will the theories prove correct? From Discover’s Cosmic Variance blog:

We have theoretical predictions about how dark matter should act, and it’s good to compare them to data. Interestingly, the fit to our favorite models is not perfect; this cluster, and a few others like it, are more dense in a central core region than simple theories predict. This is an opportunity to learn something — perhaps clusters started to form earlier in the history of the Universe than we thought, or perhaps there’s something new in the physics of dark matter that we have to start taking into account.

Astronomers will use the new “dark” map to shed light on how the Universe has evolved in the past—and will continue to evolve in the future.

Black holes in the centers of galaxies have millions or billions of times the mass of the Sun and draw in material at a high rate.

But does that material include dark matter?

About 23% of the Universe is made up of mysterious dark matter, invisible material only detected through its gravitational influence on its surroundings. In the early Universe, small clumps of dark matter seem to have attracted gas, which then coalesced into stars that eventually assembled the galaxies we see today.

Drs. Xavier Hernandez and William Lee of the National Autonomous University of Mexico modeled the way in which black holes absorb the dark matter.  They found that the rate at which this happens is very sensitive to the amount of dark matter found in the black holes’ vicinity.

If the concentration is large enough—more than a critical density of seven times the mass of our sun spread over each cubic light year of space—the black hole mass would increase so rapidly that it would swallow large amounts of dark matter. Soon the entire galaxy would be altered beyond recognition.

Since we don’t observe the galaxies altered in this way, the scientists concluded that the density of dark matter in the centers of galaxies must be a constant, smaller value. Or dark matter may behave in an entirely different way from what scientists expect. Especially around massive, hungry black holes.

Creative Commons image by Alain r

As published last week in the online edition of Nature Physics and presented Sunday at the American Physical Society’s meeting in Portland, Oregon, scientists are hoping to use a material similar to a computer chip—topological insulators—to test the existence of the axions, theoretical weak and lightweight particles that could be the dark matter that accounts for 23% of the universe.

A topological insulator is a material where electrons can travel easily on the exterior, but not the interior. This leads to unusual properties that may be important for applications such as spintronics.

And what makes all of this exciting for physicists is that they believe that the electromagnetic behavior of topological insulators is described by the very same mathematical equations that describe the behavior of axions.

According to Shoucheng Zhang of the Stanford Institute for Materials and Energy Science, “We can make observations in tabletop experiments that help us figure out the deeper mysteries of the universe.”

Although dark matter is invisible, astrophysicists observe its gravitational effects on galaxies and light from distant parts of the Universe, among other things. With its very small mass and lack of electric charge, the axion is a candidate for a mysterious dark matter particle. But despite much effort, the axion has never been observed experimentally. If these experiments succeed, it will potentially make future large-scale searches easier.

“If we ‘see’ an axion in a tabletop experiment, it will be extremely illuminating,” Zhang said. “It will help shed light on the dark matter mystery.”

Image by Hubble Space Telescope courtesy of NASA and ESA

Scientists thought that the gamma-rays outside our galaxy were jets emitted from the large black-holes found in the center of other, distant galaxies. But, data gathered with the Fermi telescope has indicated that this is wrong… Well, not entirely wrong, but about 70 percent wrong.

“Active galaxies can explain less than 30 percent of the extragalactic gamma-ray background Fermi sees,” said Marco Ajello, an astrophysicist at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford. “That leaves a lot of room for scientific discovery as we puzzle out what else may be responsible.”

Ajello and the Fermi team analyzed data acquired by Fermi’s Large Area Telescope during the observatory’s initial year in space. The first challenge was eliminating emissions from our own galaxy.

“The extragalactic background is very faint, and it’s easily confused with the bright emission from the Milky Way,” said Markus Ackermann, another member of the Fermi team who led the measurement study. “We have done a very careful job in separating the two components to determine the background’s absolute level.”

These measurements, published online yesterday in the journal Physical Review Letters, demonstrate that active galaxies turn out to be only minor players in the gamma-ray sky.

What else may contribute to the extragalactic gamma-ray background? Particle acceleration in star-forming galaxies and merging galaxies, perhaps. Also, the ever-mysterious dark matter could be a source. According to Ajello, “Dark matter may be a type of as-yet-unknown subatomic particle. If that’s true, dark matter particles may interact with each other in a way that produces gamma rays.”

Improved analysis and continued observations will enable scientists to address these potential contributions. Meanwhile, Fermi will stay on the job, looking for more surprises in the gamma-ray sky.