Could Nearby Dwarf Galaxy be a Dark Matter Factory?

A dwarf galaxy orbiting the Milky Way is humming with gamma rays, leading astronomers to hypothesize that it could be filled with annihilating dark matter particles.

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Dark matter is thought to make up for 85 percent of all the mass in the known universe. By looking at the spin of galaxies and the interactions inside galactic clusters, an invisible type of matter exerts a powerful gravitational pull on local space. But because dark matter does not interact with normal (‘bayonic') matter via the electromagnitic force, it cannot be seen and therefore its nature remains highly mysterious.

One leading hypothesis of the source of dark matter is that of weakly-interacting massive particles, or WIMPS. These particles have yet to be discovered, but if they are out there they could account for the bulk of the universal missing mass.

WIMPS, when they collide, are theorized to annihilate. One of the byproducts of this annihilation is energy in the form of gamma rays. But simply scanning the cosmos for sources of WIMP-generated gamma rays is a difficult task as there are many other phenomena out there that also generate gamma ray radiation.

That's where dwarf galaxies come in.

Known gamma ray sources include black holes and pulsars, making the identification of annihilating WIMPs a precarious task. But ancient dwarf galaxies are known to lack a large number of these sources, making them key hunting grounds for the signature of dark matter. "They're basically very clean and quiet systems," said Savvas Koushiappas of Brown University in a press release.

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"In the search for dark matter, gamma rays from a dwarf galaxy have long been considered a very strong signature," he added. "It seems like we may now be detecting such a thing for the first time."

Located only 98,000 light-years away, the dwarf galaxy Reticulum 2 is one of the closest dwarf galaxies found to date and it has become the focus of the dark matter search. Through the analysis of observational data from NASA's Fermi Gamma-ray Space Telescope, Koushiappas and Carnegie Mellon University colleagues Alex Geringer-Sameth and Matthew Walker realized that Reticulum 2 was generating gamma rays at a rate far higher than any known gamma ray source.

"Something in the direction of this dwarf galaxy is emitting gamma rays," said Geringer-Sameth, the study's lead author. "There's no conventional reason this galaxy should be giving off gamma rays, so it's potentially a signal for dark matter."

Seeking the nature of dark matter has been maddeningly difficult, so when a predicted signature of the annihilation of WIMPs in a dwarf galaxy right next door to the Milky Way is revealed, it's understandable that some excitement, and guarded caution, is shown.

"The gravitational detection of dark matter tells you very little about the particle behavior of the dark matter," said Walker. "But now we may have a non-gravitational detection that shows dark matter behaving like a particle, which is a holy grail of sorts."

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In a paper submitted to the journal Physical Review Letters (available on the arXiv preprint service), Geringer-Sameth, Koushiappas and Walker make it clear that it is currently unknown why there's an excess of cosmic rays pumping out of Reticulum 2, but it could also be signs of the predicted signature generated by a concentration of WIMPs inside the dwarf galaxy.

"There did seem to be an excess of gamma rays, above what you would expect from normal background processes, coming from the direction of this galaxy," said Geringer-Sameth. "Given the way that we think we understand how gamma rays are generated in this region of the sky, it doesn't seem that those processes can explain this signal."

"The fact that there are gamma rays and also a clump of dark matter in the same direction makes it quite interesting," Walker added.

This is not the first time that dwarf galaxies have been tapped as possible dark matter factories, nor is Reticulum 2 the only place where tentative dark matter signals have been detected, but it is another tantalizing clue that we are getting closer at understanding what dark matter is, or - if another source for gamma rays inside dwarf galaxies is found - isn't.

Source: Brown University

Scientists at Brown, Carnegie Mellon, and Cambridge universities have detected gamma ray emissions from the direction of the galaxy Reticulum 2. Bright areas indicate a strong gamma ray signal coming from the direction of the galaxy, according to the researchers’ search algorithm.

Introduction

Did you own a toy race-car track as a child? Ever crash your model trains into one another just to see what happened? If you did, then congratulations, you already know some of the basic principles behind the Large Hadron Collider (LHC). Built by the European Organization for Nuclear Research (CERN), the 27-kilometer tunnel buried in the Swiss countryside exists to smash particle beams into each other at velocities approaching the speed of light. The idea is to use the resulting data to better understand the structure and origins of the universe. We're talking heavy questions and even heavier answers. Perhaps it's understandable that some critics, conspiracy theorists, crackpots and (alleged) time travelers might fear something more substantial than the Higgs boson particle. In this article, we'll run through some of the more popular misconceptions about the LHC and how little you have to fear about it causing the end of the world as we know it.

5. CERN Is Making an Antimatter Bomb

The Dan Brown detective novel (and movie adaptation) "Angels and Demons" centers on a plot to steal an antimatter bomb from CERN and blow up the Vatican with it. While the blockbuster delivered its share of action and intrigue, it fell short on facts. Two of the film's biggest mistakes revolved around antimatter's potential use as both an energy source and a weapon. Yes, when an antimatter particle comes in contact with normal matter, the two particles destroy each other and release energy. But CERN is quick to point out that the energy payoff simply isn't there. In fact, the transaction is so inefficient that scientists only get a tenth of a billionth of their invested energy back when an antimatter particle meets its matter counterpart. As for developing an antimatter bomb, the same principles apply. CERN points out that, at current production rates, it would take billions of years for the organization to produce enough antimatter to generate an explosion equal to an atomic blast.

4. Fun-sized Black Holes

Some concepts don't become tamer when you tack a "micro-" or a "mini-" prefix in front of them. For example, a mini-stroke is still an excellent reason to visit the hospital, and you'd certainly be ill advised to question the power of a minigun. So when CERN scientists mention that they might create microscopic black holes in the midst of their particle smashing, it's easy to understand some of the ensuing panic. Based on Einstein's theory of relativity, a few speculative theories lend a sheen of possibility to micro-black hole creation. The good news is that these theories also predict the micro-black holes would disintegrate immediately. If these black hole welterweights did hang around a little longer, it would take billions of years to consume the mass of a tiny grain of sand. That means no reducing the European countryside to a singularity and certainly no destroying the planet "Star Trek" style.

3. Attack of the Strangelets

Read enough space publications and your perception of the universe changes pretty fast. Once you get beyond the absurd vastness of the cosmos, you encounter such mind-rending notions as black holes, antimatter and dark matter. After you've swallowed the notion of a gigantic star collapsing into something smaller than a pinhead, it's easy to get bowled over by the idea of universe-destroying strangelets. Strange matter is presumed to be 10 million times denser than lead and was birthed during the Big Bang from the hearts of dense stars. The fear, which originated with the start-up of the Relativistic Heavy Ion Collider (RHIC) in 2000, is that the LHC will inadvertently produce strangelets -- tiny particles of strange matter -- and that these particles will swiftly convert surrounding normal matter into even more strange matter. It only takes a thousand-millionth of a second for the chain reaction to convert the entire planet. Strangelets, however, are purely speculative, and haven't surfaced in over eight years of RHIC operation. CERN says that the RHIC was far more likely to produce the theoretical matter than the LHC, so there's really no chance of it consuming the planet.

2. Time Travelers Hate It

In "Bill & Ted's Excellent Adventure," the titular slacker duo wields time travel with the logic of a 12-year-old. When Bill and Ted need a cell key to bust a few historical figures out of a modern California jail, they simply make a mental note for their future selves to travel back in time and plant the key where they can find it. While the 1989 buddy comedy is pretty much the antithesis of hard science fiction, its view of time-travel logic is shockingly similar to a 2009 theory regarding the LHC. Danish string theory pioneer Holger Bech Nielsen and Japanese physicist Masao Ninomiya, in a series of posted physics articles, laid out their theory that the Higgs boson particle is so abhorrent to nature that its future creation will send a ripple back through time to keep it from being made. Naturally, this theory summons images of T-800s, Jean-Claude Van Damme and Hermione Granger all galloping back through time to prevent future disasters, but not everyone is busy cracking jokes and reminiscing about time-travel movies. The two scientists aren't even talking about shadowy strangers from the future, but merely "something" looping back through the fourth dimension. Imagine a poorly designed bomb that, upon creation, destroys half the bomb factory. Now expand that example out from the confines of linear time.

1. Gateway to Hell

Black holes, antimatter explosions and even strangelets all originate from scientific fact and theory (albeit with a bit of imagination thrown in). Forget all that for the moment and consider the "Satan's Stargate" theory, proposed by Chris Constantine, better known on the Internet as YouTube user gorilla199. Constantine charges that the LHC exists "to disrupt a hole in the Van Allen belt that surrounds the Earth" and "to allow the return of the Annunaki from the planet Nibiru in order that they can come here, corrupt the rest of the Earth and do battle with God at Armageddon." There's also some stuff in there about freemasonry, cosmic rays and the Old Testament offspring of humans and fallen angels. According to BBC News, Constantine received a suspended sentence for DVD pirating after his defense attorney charged that Constantine suffered from a serious psychiatric condition. The Antichrist could not be reached for comment.