Discovered: Cosmic Rays from a Mysterious, NEARBY Object

Discovered: Cosmic Rays from a Mysterious, Nearby Object
Nov. 19, 2008

An international team of researchers has discovered a puzzling surplus of high-energy electrons bombarding Earth from space. The source of these cosmic rays is unknown, but it must be close to the solar system and it could be made of dark matter. Their results are being reported in the Nov. 20th issue of the journal Nature.

"This is a big discovery," says co-author John Wefel of Louisiana State University. "It's the first time we've seen a discrete source of accelerated cosmic rays standing out from the general galactic background."

Above:An artist's concept of cosmic rays hitting Earth's upper atmosphere. Credit: Simon Swordy, University of Chicago.

Galactic cosmic rays are subatomic particles accelerated to almost light speed by distant supernova explosions and other violent events. They swarm through the Milky Way, forming a haze of high energy particles that enter the solar system from all directions. Cosmic rays consist mostly of protons and heavier atomic nuclei with a dash of electrons and photons spicing the mix.

To study the most powerful and interesting cosmic rays, Wefel and colleagues have spent the last eight years flying a series of balloons through the stratosphere over Antarctica. Each time the payload was a NASA-funded cosmic ray detector named ATIC, short for Advanced Thin Ionization Calorimeter. The team expected ATIC to tally the usual mix of particles, mainly protons and ions, but the calorimeter found something extra: an abundance of high-energy electrons.

Wefel likens it to driving down a freeway among family sedans, mini-vans and trucks—when suddenly a bunch of Lamborghinis bursts through the normal traffic. "You don't expect to see so many race cars on the road—or so many high-energy electrons in the mix of cosmic rays." During five weeks of ballooning in 2000 and 2003, ATIC counted 70 excess electrons in the energy range 300-800 GeV. ("Excess" means over and above the usual number expected from the galactic background.) Seventy electrons may not sound like a great number, but like seventy Lamborghinis on the freeway, it's a significant surplus.

Above: ATIC high-energy electron counts. The triangular curve fitted to the data comes from a model of dark-matter annihilation featuring a Kaluza-Klein particle of mass near 620 GeV. Details may be found in the Nov. 20, 2008, edition of Nature: "An excess of cosmic ray electrons at energies of 300-800 Gev," by J. Chang et al.

"The source of these exotic electrons must be relatively close to the solar system—no more than a kiloparsec away," says co-author Jim Adams of the NASA Marshall Space Flight Center.

Why must the source be nearby? Adams explains: "High-energy electrons lose energy rapidly as they fly through the galaxy. They give up energy in two main ways: (1) when they collide with lower-energy photons, a process called inverse Compton scattering, and (2) when they radiate away some of their energy by spiraling through the galaxy's magnetic field." By the time an electron has traveled a whole kiloparsec, it isn't so 'high energy' any more.

High-energy electrons are therefore local. Some members of the research team believe the source could be less than a few hundred parsecs away. For comparison, the disk of the spiral Milky Way galaxy is about thirty thousand parsecs wide. (One parsec approximately equals three light years.)

"Unfortunately," says Wefel, "we can't pinpoint the source in the sky." Although ATIC does measure the direction of incoming particles, it's difficult to translate those arrival angles into celestial coordinates. For one thing, the detector was in the basket of a balloon bobbing around the South Pole in a turbulent vortex of high-altitude winds; that makes pointing tricky. Moreover, the incoming electrons have had their directions scrambled to some degree by galactic magnetic fields. "The best ATIC could hope to do is measure a general anisotropy—one side of the sky versus the other."

This uncertainty gives free rein to the imagination. The least exotic possibilities include, e.g., a nearby pulsar, a 'microquasar' or a stellar-mass black hole—all are capable of accelerating electrons to these energies. It is possible that such a source lurks undetected not far away. NASA's recently-launched Fermi Gamma-ray Space Telescope is only just beginning to survey the sky with sufficient sensitivity to reveal some of these objects.

An even more tantalizing possibility is dark matter.

There is a class of physical theories called "Kaluza-Klein theories" which seek to reconcile gravity with other fundamental forces by positing extra dimensions. In addition to the familiar 3D of human experience, there could be as many as eight more dimensions woven into the space around us. A popular yet unproven explanation for dark matter is that dark matter particles inhabit the extra dimensions. We feel their presence via the force of gravity, but do not sense them in any other way.

How does this produce excess cosmic rays? Kaluza-Klein particles have the curious property (one of many) that they are their own anti-particle. When two collide, they annihilate one another, producing a spray of high-energy photons and electrons. The electrons are not lost in hidden dimensions, however, they materialize in the 3-dimensions of the real world where ATIC can detect them as "cosmic rays."

"Our data could be explained by a cloud or clump of dark matter in the neighborhood of the solar system," says Wefel. "In particular, there is a hypothesized Kaluza-Klein particle with a mass near 620 GeV which, when annihilated, should produce electrons with the same spectrum of energies we observed."

Testing this possibility is nontrivial because dark matter is so, well, dark. But it may be possible to find the cloud by looking for other annihilation products, such as gamma-rays. Again, the Fermi Space Telescope may have the best chance of pinpointing the source.

"Whatever it is," says Adams, "it's going to be amazing."

For more information about this research, see "An excess of cosmic ray electrons at energies of 300-800 Gev," by J. Chang et al. in the Nov. 20, 2008, issue of Nature.

Click to expand...

Clump of dark matter may loom near solar system
By Will Dunham
Wed Nov 19, 4:25 pm ET

WASHINGTON (Reuters) – A balloon-borne instrument soaring high over Antarctica has found evidence of a possible large clump of mysterious so-called dark matter relatively close to our solar system, scientists said on Wednesday.

It detected an unexpected amount of very high energy cosmic ray electrons coming from an unknown source within about 3,000 light years of the solar system. A light-year is 6 trillion miles (10 trillion km), the distance light travels in a year.

One explanation is that the electrons may have been spawned as dark matter particles collided with one another, triggering their mutual annihilation, according to Louisiana State University physics professor John Wefel.

Scientists think perhaps 25 percent of the universe is made up of dark matter, which responds to gravity the same way as does regular matter such as stars and planets and the like.

While the stuff is thought to be strewn throughout the cosmos, it is invisible and poorly understood. Scientists have struggled to find any solid evidence of dark matter, and the new study could represent a major step forward in that effort.

"This would be the first indirect detection of the annihilation signature of predicted dark matter particles," Wefel, who helped lead the research published in the journal Nature, said in a telephone interview.

Scientists think regular matter amounts to about 5 percent of the universe's mass. The remaining roughly 70 percent is thought to be composed of dark energy, a mysterious presence that may be making the universe expand at an accelerated pace.

The scientists said it is possible that the electrons detected in this research may have been produced by a more conventional source -- perhaps a spinning neutron star called a pulsar that emits a beam of radiation, a medium-sized black hole or the remnants of a bygone supernova.

Scientists think dark matter is distributed somewhat uniformly throughout the universe, with clumps forming around concentrations of regular matter -- for example, galaxies -- due to their gravitational pull.

The scientists think the electrons detected by the instrument may come from one of these clumps located relatively close in astronomical terms to our solar system.

"If our data is to be explained this way, there's got to be some sort of a clump," Wefel said.

The electrons detected by the instrument seem to match theories about what would be produced when dark matter particles collide and destroy each other.

"The annihilation of these exotic particles with each other would produce normal particles such as electrons, positrons, protons and antiprotons that can be observed by scientists," Eun-Suk Seo of the University of Maryland said in a statement.

The NASA-funded instrument was carried to an altitude of about 24 miles above Antarctica using a helium-filled balloon as big as the interior of a large sports stadium.

The research was part of the Advanced Thin Ionization Calorimeter, or ATIC, collaboration involving scientists in the United States, Germany, Russia and China.

Click to expand...

Rex Jackson said:

"An even more tantalizing possibility is dark matter."

how about "An even more tantalizing possibility is some sort of weapon or tool"??

Click to expand...

December 6, 2008 - Two Cosmic Ray Hot Spots
Never Seen from Earth Before.
“This discovery calls into question our understanding of cosmic rays
and raises the possibility that an unknown source or magnetic effect near our
solar system is responsible for these observations.”
- John Pretz, Ph.D., Los Alamos National Laboratory



The Los Alamos National Laboratory Milagro cosmic-ray observatory was constructed in a water pond atop Fenton Hill west of Los Alamos, New Mexico. It is a telescope without lenses and mirrors. The instrument is the size of a football field with a protective cover to keep out light. Any cosmic ray that hits the pond flashes light that is recorded by the Milagro telescope under water. Until now, scientists thought cosmic rays came randomly from all over the cosmos. The new LANL research published in the November 24, 2008, Physical Review Letters, shows two regions near the bulls eye of the constellation Taurus and near the constellation Gemini are firing out cosmic rays more intensely than any other region. The puzzle is why? And what is the source?

An international team of researchers, using Los Alamos National Laboratory's
Milagro Observatory, has discovered for the first time two distinct hot spots (red regions)
that appear to be bombarding Earth with an excess of cosmic rays near the
Orion constellation (white diagram). Image credit John Pretz, LANL.

Click to expand...

Peanut said:

space ghost farts?

Click to expand...

Rex Jackson said:

I would guess something like this could be heating the planet a bit. I wonder if other planets are experiencing this too.

Click to expand...