MAP

Friday, 29 August 2014

THE SUN AS BOREXINO SEES IT IN REAL TIME The neutrino experiment in the INFN Gran Sasso Laboratories has managed to measure the energy of our star in real time: the energy released today at the centre of the Sun is exactly the same as that produced 100,000 years ago

For the first time in the history of scientific investigation of our star, solar energy has been measured at the very moment of its generation. This has been announced by the Borexino experiment at the Gran Sasso National Laboratories (LNGS) of the Italian National Institute for Nuclear Physics (INFN). The study is published on August 28th, 2014 in the prestigious international journal Nature.
Borexino has managed to measure the Sun’s energy in real-time, detecting the neutrinos produced by nuclear reactions inside the solar mass: these particles, in fact, take only a few seconds to escape from it and eight minutes to reach us. Previous measurements of solar energy, on the other hand, have always taken place on radiation (photons) which currently illuminate and heat the Earth and which refer to the same nuclear reactions, but which took place over a hundred thousand years ago: this, in fact, is the time it takes, on average, for the energy to travel through the dense solar matter and reach its surface. The comparison between the neutrino measurement now published by Borexino and the previous measurements concerning the emission of radiant energy from the Sun shows that solar activity has not changed in the last one hundred thousand years. "Thanks to the results of this new Borexino research we have seen, via the neutrinos produced in the proton-proton (pp) reaction, that it is the chain of pp nuclear fusions which makes the Sun work, providing precisely the energy that we measure with photons: in short, this proves that the Sun is an enormous nuclear fusion plant," says Gianpaolo Bellini, one of the fathers of the Borexino experiment.
The Borexino detector, installed in the INFN underground Laboratories of Gran Sasso, has managed to measure the flux of neutrinos produced inside the Sun in the fusion reaction of two hydrogen nuclei to form a deuterium nucleus: this is the seed reaction of the nuclear fusion cycle which produces about 99% of the solar energy. Up until now, Borexino had managed to measure the neutrinos from nuclear reactions that were part of the chain originated by this reaction or belonging to secondary chains, which contribute significantly less to the generation of solar energy, but which were key to the discovery of certain crucial physical properties of this "ephemeral" elementary particle, the neutrino.
The difficulty of the measurement just made is due to the extremely reduced energy of these neutrinos (they have, in fact, a maximum energy of 420 keV), the smallest one compared to the other neutrinos emitted by the Sun, which also have energy levels so low as to make it almost impossible to measure them and which only Borexino was and is able to measure. This performance makes Borexino a detector unique in the world, and it will remain so for a number of years, thanks to state-of-the-art technologies used in its construction, which have allowed not only the neutrinos emitted from the Sun but also those produced by our Earth to be studied.

The Borexino experiment is the result of a collaboration between European countries (Italy, Germany, France, Poland), the United States and Russia and it will take data for at least another four years, improving the accuracy of measurements already made and addressing others of great importance for both particle physics as well as astrophysics.

Wednesday, 27 August 2014

Long-sought neutrinos answer burning question about the Sun Underground lab catches low-energy particles that reveal crucial proton-proton fusion reaction. Ron Cowen 27 August 2014

After decades of searching, physicists have finally confirmed the existence of low-energy neutrinos that are direct evidence for the first crucial step in the nuclear reaction that makes the Sun shine. While the detection validates well-established stellar fusion theory, future, more sensitive versions of the experiment could look for deviations from the theory that would reveal new physics. The conversion of hydrogen into helium is the source of 99% of the Sun’s energy. The multistep process begins when the star’s hot, dense core squeezes two protons together to form deuterium, a heavy isotope of hydrogen with a nucleus made of one proton and one neutron. One of the fused protons then transforms into a neutron, a process that releases a neutrino and a positron (the antimatter counterpart of the electron).
While the positrons are almost instantly annihilated in collisions with electrons, the neutrinos zip through matter unscathed, so they escape straight into outer space, radiating in all directions at nearly the speed of light. Other nuclear reactions in the Sun also produce neutrinos, and 100 billion of the particles bombard each square centimetre of Earth every second. The proton–proton reaction accounts for 90% of all solar neutrinos, but the neutrinos it emits have relatively low energy, and their signal can be swamped by the radioactive decay of ordinary terrestrial materials. Thus, although more-energetic solar neutrinos have been detected since the 1960s, those from the proton–proton reaction had eluded detection so far.
Now, the Borexino detector, housed beneath more than a kilometre of rock at the Gran Sasso National Laboratory near L'Aquila, Italy, has succeeded in detecting the neutrinos that accompany the proton-proton reaction at the solar core. Physicist Andrea Pocar of the University of Massachusetts Amherst and his collaborators report the findings in Nature1.
Although solar physicists had a general understanding of the Sun's nuclear reactions, they could have been mistaken about exactly which reactions take place and their relative importance. That would have left the question of how the Sun shines incompletely answered, says Michael Smy, a neutrino physicist at the University of California, Irvine. For this reason, the Borexino collaboration's direct detection of the neutrinos “is a landmark achievement”, he says.
Star light, star bright
The finding not only confirms how some 90% of the stars in the Milky Way — including those similar to the Sun but also many that are less massive — generate most of their energy, but provides a near-instantaneous snapshot of the solar core, since the neutrinos arrive at Earth just 8 minutes after they are created.
The core of the Borexino experiment features a nylon vessel containing 278 tonnes of an ultrapure benzene-like liquid that emits flashes of light when electrons are scattered by neutrinos. The liquid was derived from a crude-oil source nearly devoid of radioactive carbon-14, which can hide the neutrino signal. The detector fluid is surrounded by 889 tonnes of non-scintillating liquid that shields the vessel from spurious radiation emitted by the experiment's 2,212 light detectors.
Borexino can measure the flux of low-energy neutrinos with a precision of 10%. Future experiments could bring that down to 1%, providing a demanding test of theoretical predictions and thus potentially uncovering new physics.
For example, tiny mismatches between the rate of energy production indicated by neutrino detection and the energy from photons in the sunlight that reaches Earth could signify the presence of dark matter, the hypothetical invisible material believed to account for most of the mass in the Universe, says astrophysicist Aldo Serenelli of the Institute of Space Sciences in Bellaterra, Spain. Experiments may also be able to test how well models describe the transformation of electron neutrinos into two other types — tau neutrinos and muon neutrinos — as they travel from the solar core.

Nature doi:10.1038/nature.2014.15779

Mysterious source of ozone-depleting chemical baffles NASA

A chemical used in dry cleaning and fire extinguishers may have been phased out in recent years but NASA said Wednesday that carbon tetrachloride (CCl4) is still being spewed into the atmosphere from an unknown source.

 The world agreed to stop using CC14 as part of the Vienna Convention on Protection of the Ozone Layer and its Montreal Protocol, which attained universal ratification in 2009.
"Parties to the Montreal Protocol reported zero new CCl4 emissions between 2007-2012," the US space agency said in a statement.
"However, the new research shows worldwide emissions of CCl4 average 39 kilotons per year, approximately 30 percent of peak emissions prior to the international treaty going into effect."
CC14 levels are not enough to reverse the decreasing trend of ozone-depletion, but experts are still mystified as to where it is coming from.
With no new reported emissions, atmospheric concentrations of the compound should have declined at an expected rate of four percent per year since 2007.
However, observations from the ground showed atmospheric concentrations were only declining one percent per year.
"We are not supposed to be seeing this at all," said Qing Liang, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
"It is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources."
Researchers used NASA's 3-D GEOS Chemistry Climate Model and data from global networks of ground-based observations to establish the first estimate of average global CC14 emissions from 2000 to 2012.
In going through the data, researchers also learned that the chemical stays in the atmosphere were 40 percent longer than previously thought.
"People believe the emissions of ozone-depleting substances have stopped because of the Montreal Protocol," said Paul Newman, chief scientist for atmospheres at NASA.
"Unfortunately, there is still a major source of CCl4 out in the world."

The study was published in the journal Geophysical Research Letters.

Wednesday, 20 August 2014

“COMPUTER MODEL SHOWS MOON'S CORE SURROUNDED BY LIQUID AND IT'S CAUSED BY EARTH'S GRAVITY” Jul 28, 2014 by Bob Yirka

(Phys.org) —A team of researchers with team members from China, the U.S. and Japan has created a computer model that shows that the moon is not solid all the way through—instead, it shows a liquid layer surrounding the core. In their paper published in the journal Nature Geoscience, the team suggests the liquid layer, if it's really there, is caused by friction due to Earth's gravity.
Scientists have noted anomalies in measurements of the moon's orbit and associated gravitational readings for some time. Such anomalies have defied explanation, however, as models built to replicate them have generally produced results that weren't very clear. At root however, has been the idea that the moon's core may be covered by a thin layer of liquid. The team noted that gravitational readings of the moon indicate that there is rotation at the core that is not the same as other rotation measurements near the core. This suggests a liquid outer layer.
To getter a better idea of what might be going on at the moon's center, the researchers built a computer model that takes into account the gravity exerted by the moon, the earth and the sun. When set into motion, the model showed that a liquid layer over the core gave the same gravity readings as scientists have found when measuring the real moon. This suggests, the team reports, that a liquid layer does truly exist, and likely has been there for a very long time.
As for why such a layer would exist, the team suggests that the tug of Earth's gravity—tidal heating—is likely playing a role, causing friction between the core and material above it, resulting in the creation and maintenance of a liquid layer.

A lot more research will have to be done, of course, before scientists accept the results of the computer model. But if such research should prove that there is a liquid layer, scientists might have to do some rethinking of theories that describe the origin of the moon. If the moon was created due to a large body striking Earth, why did it not cool down over the four and half billion years since then, to the extent that it would be too cold for a liquid layer to exist today?

Sunday, 15 June 2014

WHY ISN’T THE ASTEROID BELT A PLANET? by Fraser Cain on June 11, 2014

It seems like there’s a strange gap in between Mars and Jupiter filled with rocky rubble. Why didn’t the asteroid belt form into a planet, like the rest of the Solar System?
Beyond the orbit of Mars lies the asteroid belt its a vast collection of rocks and ice, leftover from the formation of the solar system. It starts about 2 AU, ends around 4 AU. Objects in the asteroid belt range from tiny pebbles to Ceres at 950 km across.
Star Wars and other sci-fi has it all wrong. The objects here are hundreds of thousand of kilometers apart. There’d be absolutely no danger or tactical advantage to flying your spacecraft through it.
To begin with, there actually isn’t that much stuff in the asteroid belt. If you were to take the entire asteroid belt and form it into a single mass, it would only be about 4% of the mass of our Moon. Assuming a similar density, it would be smaller than Pluto’s moon Charon.
There’s a popular idea that perhaps there was a planet between Mars and Jupiter that exploded, or even collided with another planet. What if most of the debris was thrown out of the solar system, and the asteroid belt is what remains?
We know this isn’t the case for a few of reasons. First, any explosion or collision wouldn’t be powerful enough to throw material out of the Solar System. So if it were a former planet we’d actually see more debris.
Second, if all the asteroid belt bits came from a single planetary body, they would all be chemically similar. The chemical composition of Earth, Mars, Venus, etc are all unique because they formed in different regions of the solar system. Likewise, different asteroids have different chemical compositions, which means they must have formed in different regions of the asteroid belt.
In fact, when we look at the chemical compositions of different asteroids we see that they can be grouped into different families, with each having a common origin. This gives us a clue as to why a planet didn’t form where the asteroid belt is.
If you arrange all the asteroids in order of their average distance from the Sun, you find they aren’t evenly distributed. Instead you find a bunch, then a gap, then a bunch more, then another gap, and so on. These gaps in the asteroid belt are known as Kirkwood gaps, and they occur at distances where an orbit would be in resonance with the orbit of Jupiter.

Jupiter’s gravity is so strong, that it makes asteroid orbits within the Kirkwood gaps unstable. It’s these gaps that prevented a single planetary body from forming in that region. So, because of Jupiter, asteroids formed into families of debris, rather than a single planetary body.

Saturday, 14 June 2014

Hubble Hubba: Stars Are Being Born Around A Black Hole In Galaxy’s Center by ELIZABETH HOWELL on JUNE 13, 2014

Let’s just casually look at this image of a galaxy 86 million light-years away from us. In the center of this incredible image is a bright loop that you can see surrounding the heart of the galaxy. That is where stars are being born, say the scientists behind this new Hubble Space Telescope image. “Compared to other spiral galaxies, it looks a little different,” NASA stated. “The galaxy’s barred spiral center is surrounded by a bright loop known as a resonance ring. This ring is full of bright clusters and bursts of new star formation, and frames the supermassive black hole thought to be lurking within NGC 3081 — which glows brightly as it hungrily gobbles up in-falling material.”
A “resonance ring” refers to an area where gravity causes gas to stick around in certain areas, and can be the result of a ring (like you see in NGC 3081) or close-by objects with a lot of gravity. Scientists added that NGC 3081, which is in the constellation Hydra or the Sea Serpent, is just one of many examples of barred galaxies with this type of resonance.
By the way, this image is a combination of several types of light: optical, infrared and ultraviolet.

Thursday, 5 June 2014

Thursday, 3 April 2014

"Moon's Age Revealed, and a Lunar Mystery May Be Solved" - By Charles Q. Choi, Space.com Contributor | April 02, 2014 01:01pm ET

Scientists have pinned down the birth date of the moon to within 100 million years of the birth of the solar system — the best timeline yet for the evolution of our planet's natural satellite.
This new discovery about the origin of the moon may help solve a mystery about why the moon and the Earth appear virtually identical in makeup, investigators added.
Scientists have suggested the moon was formed4.5 billion years ago by a gigantic collision between a Mars-size object named Theiaand Earth, a crash that would have largely melted the  Earth. This model suggested that more than 40 percent of the moon was made up of debris from this impacting body. (Current theory suggests that Earth experienced several giant impacts during its formation, with the moon-forming impact being the last.) [How the Moon Was Born: A Photo Timeline]
However, researchers suspected Theia was chemically different from Earth. In contrast, recent studies revealed that the moon and Earth appear very similarwhen it comes to versions of elements called isotopes — more so than might be suggested by the current impact model. (Isotopes of an element have differing numbers of neutrons from one another.)
"This means that at the atomic level, the Earth and the moon are identical,"study lead author Seth Jacobson, a planetary scientist at the Côte d'Azur Observatory in Nice, France, told Space.com. "This new information challenged the giant impact theory for lunar formation."
How the moon evolved
No one seriously disputed an impact as the most likely scenario for the formation of the moon, Jacobson said. However, a virtually atomically identical moon and Earth threw the exact circumstances of the collision into question, he said.
Now, by pinpointing when the moon formed, Jacobson and his colleagues could help explain why the moon and Earth are mysteriously similar. The scientists detailed their findings in the April 3 issue of the journal Nature. [How the Moon Formed: 5 Wild Lunar Theories]
Efforts to date the moon-forming impact have proposed a range of ages. Some have argued for an early event, about 30 million years after the birth of the solar system, whereas others suggested that it occurred more than 50 million years and possibly as much as 100 million years after the solar system formed.
To help solve this mystery, Jacobson and his colleagues simulated the growth of the solar system's rocky planets — Mercury, Venus, Earth and Mars — from a protoplanetary disk of thousands of planetary building blocks orbiting the sun.
By analyzing how these planets formed and grew from more than 250 computer simulations, the researchers discovered that if the moon-forming impact was early, the amount of material accreted onto Earth afterward was large. If the impact was late, the amount would then be small.
Past research had calculated the amount of material accreted onto Earth after the moon-forming impact. These estimates are based on how on how so-called highly siderophile or "iron-loving" elements such as iridium and platinum show a strong tendency to move into Earth's core. After each giant impact the nascent Earth sustained, these elements would have leached from Earth's mantle and bonded with heavy, iron-rich material destined to sink to Earth's heart.
Moon birth mystery
After the last giant impact that formed the moon, the mantle should have been almost completely stripped of iridium, platinum and their cousins. These elements are still present in the mantle, but only in small amounts, which suggests only a small amount of material accreted onto Earth after the moon-forming impact.
The researchers calculated the moon-forming impact must have occurred about 95 million years after the formation of the solar system, give or take 32 million years.
"A late moon-forming event, as suggested by our work, is very consistent with an identical Earth and moon," Jacobson said.
In addition, recent analyses propose that the impact that created the moon required a faster, more energetic collision than previously suggested. This makes sense if the impact took place relatively late with an older protoplanetary disk, as the new findings suggest.
"Older disks tend to be dynamically more active, since there are fewer bodies left in the disk to distribute energy amongst," Jacobson said.
These new findings raise an interesting new puzzle. While they suggest the moon and the Earth formed together nearly 100 million years after the solar system arose, evidence from meteorites from Mars suggests that the Red Planet formed as little as a few million years after the solar system was born.
"This means that Earth and Mars formed over dramatically different timescales, with Mars forming much faster than the Earth," Jacobson said. "How can this be? Is it just a matter of size? Location? What about Mercury and Venus? Did they grow on similar timescales to the Earth or on timescales more similar to Mars? I think these are some of the really important questions that we, as a community of planetary scientists, will be addressing in the future."

Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Wednesday, 2 April 2014

Case for Dark Matter Signal Strengthens - By: Natalie Wolchover March 3, 2014 - [simonsfoundation.org/quanta]

Not long after the Fermi Gamma-ray Space Telescope took to the sky in 2008, astrophysicists noticed that it was picking up a steady rain of gamma rays pouring outward from the center of the Milky Way galaxy. This high-energy radiation was consistent with the detritus of annihilating dark matter, the unidentified particles that constitute 84 percent of the matter in the universe and that fizzle upon contact with each other, spewing other particles as they go. If the gamma rays did in fact come from dark matter, they would reveal its identity, resolving one of the biggest mysteries in physics. But some argued that the gamma rays could have originated from another source.
Now a new analysis of the signal claims to rule out all other plausible explanations and makes the case that the gamma rays trace back to a type of particle that has long been considered the leading dark matter candidate — a weakly interacting massive particle, or WIMP. Meanwhile, a more tentative X-ray signal reported in two other new studies suggests the existence of yet another kind of dark matter particle called a sterile neutrino.
In the new gamma-ray analysis, which appeared Feb. 27 on the scientific preprint site arXiv.org, Dan Hooper and his collaborators used more than five years’ worth of the cleanest Fermi data to generate a high-resolution map of the gamma-ray excess extending from the center of the galaxy outward at least 10 angular degrees, or 5,000 light-years, in all directions.
“The results are extremely interesting,” said Kevork Abazajian, an associate professor of physics and astronomy at the University of California, Irvine. “The most remarkable part of the analysis is that the signal follows the shape of the dark matter profile out to 10 degrees,” he said, explaining that it would be “very difficult to impossible” for other sources to mimic this predicted dark matter distribution over such a broad range.
The findings do not constitute a discovery of dark matter, the scientists said, but they prepare the way for an upcoming test described by many researchers as a “smoking gun”: If the gamma-ray excess comes from annihilating WIMPs, and not conventional astrophysical objects, then the signal will also be seen emanating from dwarf galaxies that orbit the Milky Way — diffuse objects that are rich in dark matter but not in other high-energy photon sources such as pulsars, rotating neutron stars that have been floated as alternative explanations for the excess.
“These gamma rays match the predictions of a pretty prototypical WIMP, the kind of thing we were all writing down 10 or 15 years ago,” said Hooper, a theoretical astrophysicist at the Fermi National Accelerator Laboratory and the University of Chicago, and the person who co-discovered the gamma-ray excess with then graduate student Lisa Goodenough in 2009. “That’s where my money is.”
“It’s definitely exciting,” said Neal Weiner, a dark matter specialist at New York University. “I think we’d like to see it somewhere else, like a dwarf galaxy, before getting really excited.”
Preliminary results from the Fermi Collaboration — scientists who process, analyze and release the telescope data — offer hints that there may indeed be a surplus of gamma rays coming from the dwarf galaxies. Although there is currently too little data to determine whether an excess exists, “we are starting to get closer to the range,” said Jennifer Siegal-Gaskins, a physicist at the California Institute of Technology and a member of the Fermi Collaboration. “I would say the next couple of years of data could really be important for testing this excess.”
“If that small excess from the dwarf galaxies turns to a big one, that would convince the whole community,” Hooper said. “That would be game over.”
While most experts agree, some question whether indirect glimpses of dark matter can ever truly constitute a discovery.
Dark matter consists of elementary particles that do not emit or absorb light, because they do not experience the electromagnetic force. These particles are also unaffected by the strong nuclear force, which ensnares many of the known particles into atoms. Cosmologists infer the existence of dark matter, and can model its distribution throughout the cosmos, because it does participate in the force of gravity and therefore plays a leading role in shaping galaxies. If dark matter particles also experience the fourth and final force of nature, called the weak nuclear force, then they are of a type known as a WIMP.
In many theories, pairs of WIMPs can annihilate each other on contact, emitting other particles as they go. If the glimmer of gamma rays from the inner galaxy is the afterglow from such annihilations, then their detected energy levels indicate that they most likely originate from WIMPs with a mass of 35 giga-electron-volts (GeV) annihilating into quarks, or 10-GeV WIMPs annihilating into tau particles.
The 35-GeV WIMP model “fits the data best,” said Tracy Slatyer, an assistant professor of physics at the Massachusetts Institute of Technology and a co-author of the new paper. The fit has greatly improved, she said, since the group’s last analysis of the gamma-ray excess. If the signal wasn’t from dark matter, “it’s not at all clear that going to a better data sample would make the results look better,” she said, “but when I saw the new results, I was amazed.”
WIMPs have not yet shown up in direct detection experiments, which look for spurts of energy coming from their weak interactions with atomic nuclei, usually in detectors placed in mine shafts deep underground to lower the background noise. But this does not mean 35-GeV WIMPs don’t exist, scientists said, because no one knows how frequently they interact. The authors of the new study “could be perfectly right, and we just need detectors two orders of magnitude more sensitive to see the particles,” said Juan Collar, an associate professor of physics at the University of Chicago who helps develop direct detection experiments.
Most of the researchers interviewed for this article said the presence of a gamma-ray excess from the dwarf galaxies would be sufficient proof of WIMPs, but a few said that it might take a direct detection to convince them. “The problem is the universe is a messy place,” said Kathryn Zurek, an associate professor of physics at the University of Michigan. Try as they might to rule out “astrophysics” — shorthand among dark matter researchers for all the conventional stuff in the sky, from pulsars to supernovae to the sun — it is always possible that they have missed something.
The study authors, however, are confident that dark matter is the only plausible source of the gamma rays. “We threw everything including the kitchen sink at the problem,” Hooper said. “My views are on the record.”
Meanwhile, just as Hooper’s group was putting the finishing touches on the new manuscript, two other teams of scientists independently reported the discovery of a different anomaly in the sky: a dash of X-rays emanating from distant galaxies that is consistent with the decay of 7-kilo-electron-volt (keV) sterile neutrinos — heavier and less active cousins of the familiar neutrinos that are also dark matter candidates.
Esra Bulbul, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, and her colleagues spotted the X-rays in data from the Chandra and XMM-Newton space telescopes and published their results Feb. 10. A week later, a group led by Alexey Boyarsky of the University of Leiden in the Netherlands reported the same X-ray excess in telescope observations of the Andromeda galaxy.
“I think we have a very big fish here,” Bulbul said.
Bulbul and colleagues report a statistical significance of between 4 and 5 sigma, meaning the X-ray signal is strong enough that the odds that it is a random fluke are only one in 100,000. However, putative dark matter signals often hover at the 4-sigma brink of statistical significance only to fade into the background when more data is collected. Seasoned veterans of this boom-and-bust cycle are skeptical about the new anomaly, but some have expressed cautious optimism.
“It’s definitely intriguing,” said John Beacom, a theoretical astrophysicist at Ohio State University. “They certainly have tried very hard to eliminate or examine the possibility of an atomic transition being the cause. They’ve also gone to great lengths to eliminate instrumental effects.”
The X-ray bump appeared in all subsets of the data, no matter how Bulbul and colleagues sliced it — a sign that the bump did not come from a bias somewhere in the telescope instrumentation. It was this same omnipresence that convinced particle physicists at the Large Hadron Collider that they had cornered the Higgs boson in 2012 before their signal reached the 5-sigma strength formally needed for a discovery. Further support for the significance of the X-ray excess comes from the Dutch group’s discovery of the same bump at 4.4-sigma strength in a different data set.
If the X-rays come from sterile neutrinos, the existence of these particles would very likely solve a long-standing puzzle about galaxy formation known as the “too big to fail” problem, which asks why objects called dark matter subhalos don’t collapse and form dwarf galaxies. “That’s one of the reasons I’m actually more excited about this result than I would be otherwise,” Abazajian said. The particles also play a role in the seesaw mechanism, the most widely supported explanation for the minuscule mass of regular neutrinos. Decays of sterile neutrinos shortly after the Big Bang could even explain the mysterious dominance of matter over antimatter in the universe today. “Sterile neutrinos get invoked for twenty different reasons,” Beacom said.
Like the gamma-ray signal, the X-ray excess will face a clear-cut test in the near future. The Astro-H telescope, set for launch in 2015, will be sensitive enough to detect the smear of the signal. If the width of the bump is consistent with the expected speed of decaying dark matter particles, “that would be a detection,” Abazajian said.
Both signals are tough to dismiss, raising a strange prospect. “It’s possible they are both dark matter,” Abazajian said. “It would be crazy, but it’s certainly possible.”
The sterile neutrinos associated with the X-rays could account for anywhere from 1 to 100 percent of dark matter, depending on how often they decay. And the WIMPs tied to the gamma rays are almost as flexible. The two could coexist. As Collar put it, “If the matter we know about is so rich in families of particles, what tells you this dark sector we know nothing about is not as rich or richer?”
A theoretical model called “exciting dark matter,” proposed in 2007 by Weiner and Douglas Finkbeiner of Harvard, a co-author of the new gamma-ray paper, even predicts the existence of both a keV-scale dark matter particle and a GeV-scale particle working in tandem. “So, at the moment, I’m quite excited!” Weiner said in an email.
But at least for the next couple of years, another nagging possibility remains.
“It’s like the Monty Python sketch — nobody ever expects the Spanish Inquisition,” Beacom said. “Sometimes in this field nobody expects astrophysics, but it’s almost always astrophysics. All of these groups have tried to be very careful, but it is difficult, and nature may surprise us with astrophysics yet again.”

Correction: This article was revised on March 4, 2014, to reflect that the Fermi Collaboration had exclusive access to only the first years’ worth of telescope data before releasing it to the public. New data is now released weekly.

This article was reprinted on TheGuardian.com.