Suzaku explains cosmic powerhouses

These cosmic powerhouses pour out vast amounts of energy, and they accelerate particles to almost the speed of light. But very little is known about these sources because they were discovered only recently. "Understanding these objects is one of the most intriguing problems in astrophysics," says Takayasu Anada of the Institute for Space and Astronautical Science in Kanagawa, Japan. Anada is lead author of a paper presented last week at a Suzaku science conference in San Diego, Calif.

These mysterious objects have been discovered in just the last few years by an array of four European-built telescopes named the High Energy Stereoscopic System (H.E.S.S.), located in the African nation of Namibia. H.E.S.S. indirectly detects very-high-energy gamma rays from outer space. These gamma rays are the highest-energy form of light ever detected from beyond Earth, so H.E.S.S. and other similar arrays have opened up a new branch of astronomy.

The gamma rays themselves are absorbed by gases high up in Earth’s atmosphere. But as the gamma rays interact with air molecules, they produce subatomic particles that radiate a blue-colored light known as Cherenkov radiation. H.E.S.S. detects this blue light, whose intensity and direction reveals the energy and position of the gamma-ray source.

The H.E.S.S. observations were groundbreaking, but the array’s images aren’t sharp enough to reveal the exact location where particles are being accelerated or how the particles are being accelerated. To solve this problem, several teams aimed Suzaku in the direction of some of these H.E.S.S. sources. Any object capable of emitting high-energy gamma rays will also produce X-rays, and Suzaku is particularly sensitive to high-energy (hard) X-rays.

When Anada and his colleagues pointed Suzaku at a source known as HESS J1837-069 (the numerals express the object’s sky coordinates), the X-ray spectrum closely resembled X-ray spectra of pulsar wind nebulae — gaseous clouds that are sculpted by winds blown off by collapsed stars known as pulsars. Pulsar wind nebulae emit hard X-rays, and their X-ray output remains relatively constant over long timescales. "The origin of the gamma-ray emission from HESS J1837-069 remains unclear, but we suspect that this source is a pulsar wind nebula from the Suzaku observation," says Anada.

NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton X-ray Observatory have revealed that other H.E.S.S. sources are also pulsar wind nebulae. These combined gamma-ray and X-ray observations are revealing that pulsar wind nebulae are more common and more energetic than astronomers had expected.

Another group, led by Hironori Matsumoto of the University of Kyoto in Japan, targeted Suzaku on HESS J1614-518. This source belongs to a class of objects known as "dark particle accelerators" because their ultrahigh energies suggest they are accelerating particles to near-light speed, turning them into cosmic rays. But what are these objects, and what kinds of particles are being accelerated?

Although the nature of these objects remains a mystery, Suzaku’s observations do reveal the identity of the particles. When electrons are accelerated to high speeds, they spiral around magnetic field lines that permeate space, generating copious X-rays. But since protons are 2,000 times more massive than electrons, they emit few X-rays. Matsumoto and his colleagues reported at the conference that HESS J1614-518 is a very weak X-ray emitter. "This result strongly suggests that high-energy protons are being produced in this object," says Matsumoto.

Suzaku also observed two other H.E.S.S. dark particle accelerators, but found no obvious X-ray counterparts at the H.E.S.S. positions. These sources must also be weak X-ray emitters, indicating they are accelerating mostly protons. As Matsumoto says, "Using the high sensitivity of the Suzaku satellite, we can find strong candidates for the origin of cosmic rays."

Launched in 2005, Suzaku is the fifth in a series of Japanese satellites devoted to studying celestial X-ray sources. Managed by JAXA, this mission is a collaborative effort between Japanese universities and institutions and NASA Goddard.

Source: Goddard Space Flight Center

Climate change will affect public health -- a call to action
Extreme heat events (EHE), or heat waves, are the most prominent cause of weather-related human mortality in the United States, responsible for more deaths annually than hurricanes, lightning, tornadoes, floods and earthquakes combined. These events, and other climate-related changes in the worldwide environment that directly affect public health, are examined in the November issue of the American Journal of Preventive Medicine. This special issue provides a crucial state-of-the art overview of many of the issues at the intersection of climate change and health.
Eroded telomeres are behind a rare premature aging syndrome
(PhysOrg.com) -- Each time a cell divides, the protective caps at the ends of chromosomes shorten — and when these caps are gone, so are we. Now, by using an unconventional strategy to shorten telomeres in mice, researchers at Rockefeller University have not only created the first faithful mouse model for studying a rare yet fatal premature aging syndrome, but they have revealed the molecular defect behind the disease.
Old eyes can learn new tricks; findings offer hope for adults with 'lazy eye'
New evidence that the brain regions responsible for vision are capable of adapting in adults offers new hope for those with an untreated condition commonly known as lazy eye. Also called amblyopia, the condition is the most prevalent cause of visual impairment in a single eye, affecting about six million people in the United States alone.
Major 'missed' biochemical pathway emerges as important in virtually all cells
A new study by Duke University researchers provides more evidence that the nitric oxide (NO) system in the life of a cell plays a key role in disease, and the findings point to ways to improve treatment of illnesses such as heart disease and cancer.
Old antibiotic may find new life as a stroke treatment
An old intravenous antibiotic may have new life as a stroke treatment, researchers say. Minocycline appears to reduce stroke damage in multiple ways – inhibiting white blood cells and enzymes that, at least acutely, can destroy brain tissue and blood vessels, respectively, says Dr. David Hess, chair of the Department of Neurology in the Medical College of Georgia School of Medicine. The broad-spectrum antibiotic also seems to reduce cell suicide in the minutes and hours following a stroke, enabling more cells to recover.
The new boss ... same as the old boss?
Facing ever-declining performance in their schools, and frustrated by reports of corruption and petty politics in the school boards, mayors and legislative bodies in the United States' largest cities have in recent years dismissed the elected boards and moved to a model of appointed boards. With cities such as Boston, Chicago, and New York City in the lead, this bold move has been mostly praised in the media and by the public.
Stem cell therapy studies for stroke, cerebral palsy prepare for clinical trials
Finding answers about optimal dosage and timing for stem cell therapy in adults with strokes and
newborns with ischemic injuries is a goal of two new federally funded studies.
Mammalian protein plays unexpected role in cell division, and perhaps cancer
The French Nobel laureate Jacques Monod famously said, “What’s true for E.coli is true for an elephant.” With this in mind, researchers at Rockefeller University set out to determine the function of Tel2, a protein originally found in yeast where it maintains the length of chromosome tips called telomeres. But one experiment after another informed the group that Tel2 in humans plays an altogether different role.

Suzaku explains cosmic powerhouses

Related stories:

News discussion: