PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

NASA study shows disks don't need planets to make patterns

2013-07-13
(Press-News.org) VIDEO: Watch the changing dust density and the growth of structure in this simulated debris disk, which extends about 100 times farther from its star than Earth's orbit around the sun....
Click here for more information.

Many young stars known to host planets also possess disks containing dust and icy grains, particles produced by collisions among asteroids and comets also orbiting the star. These debris disks often show sharply defined rings or spiral patterns, features that could signal the presence of orbiting planets. Astronomers study the disk features as a way to better understand the physical properties of known planets and possibly uncover new ones.

But a new study by NASA scientists sounds a cautionary note in interpreting rings and spiral arms as signposts for new planets. Thanks to interactions between gas and dust, a debris disk may, under the right conditions, produce narrow rings on its own, no planets needed.

"When the mass of gas is roughly equal to the mass of dust, the two interact in a way that leads to clumping in the dust and the formation of patterns," said lead researcher Wladimir Lyra, a Sagan Fellow at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "In essence, the gas shepherds the dust into the kinds of structures we would expect to be see if a planet were present."

A paper describing the findings was published in the July 11 issue of Nature.

The warm dust in debris disks is easy to detect at infrared wavelengths, but estimating the gas content of disks is a much greater challenge. As a result, theoretical studies tend to focus on the role of dust and ice particles, paying relatively little attention to the gas component. Yet icy grains evaporate and collisions produce both gas and dust, so at some level all debris disks must contain some amount of gas.

"All we need to produce narrow rings and other structures in our models of debris disks is a bit of gas, too little for us to detect today in most actual systems," said co-author Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md.

Here's how it works. When high-energy ultraviolet light from the central star strikes a clump of dust and ice grains, it drives electrons off the particles. These high-speed electrons then collide with and heat nearby gas.

The rising gas pressure changes the drag force on the orbiting dust, causing the clump to grow and better heat the gas. This interaction, which the astronomers refer to as the photoelectric instability, continues to cascade. Clumps grow into arcs, rings, and oval features in tens of thousands of years, a relatively short time compared to other forces at work in a young solar system.

A model developed by Lyra and Kuchner shows the process at work.

"We were fascinated to watch this structure form in the simulations," Lyra said. "Some of the rings begin to oscillate, and at any moment they have the offset appearance of dust rings we see around many stars, such as Fomalhaut."

In addition, dense clumps with many times the dust density elsewhere in the disk also form during the simulation. When a clump in a ring grows too dense, the ring breaks into arcs and the arcs gradually shrink until only a single compact clump remains. In actual debris disks, some of these dense clumps could reflect enough light to be directly observable.

"We would detect these clumps as bright moving sources of light, which is just what we're looking for when we search for planets," adds Kuchner.

The researchers conclude that the photoelectric instability provides a simple and plausible explanation for many of the features found in debris disks, making the job of planet-hunting astronomers just a little bit harder.



INFORMATION:



ELSE PRESS RELEASES FROM THIS DATE:

Knee cartilage repair technique shows improvement in patient outcomes and regeneration

2013-07-13
A natural tissue graft can spur regeneration of cartilage and improve symptoms in patients who have cartilage damage in their knee, according to a study by researchers from Hospital for Special Surgery. The new research, the first case-series evaluation of De Novo NT Natural Tissue Graft, will be presented at the annual meeting of the American Orthopaedic Society for Sports Medicine (AOSSM), to be held July 11-14, in Chicago. "The results at this time are encouraging," said lead author of the study Scott Rodeo, M.D., orthopedic surgeon and co-chief of the sports medicine ...

Study finds surprising benefits about dairy cow inflammation

2013-07-12
MANHATTAN, Kan. -- Inflammation. The word typically has a negative connotation. Arthritis … infection … numerous maladies come to mind. But a Kansas State University researcher found that inflammation that occurs naturally in dairy cows the first few days after giving birth may play a surprisingly beneficial role in the complex process of going from late pregnancy to lactation. "We know that during the first several days after giving birth and going into the lactating phase, dairy cows naturally experience some degree of inflammation," said Barry Bradford, associate ...

50-year-old assumptions about strength muscled aside

2013-07-12
LEMONT, Ill. – Doctors have a new way of thinking about how to treat heart and skeletal muscle diseases. Body builders have a new way of thinking about how they maximize their power. Both owe their new insight to high-energy X-rays, a moth and cloud computing. The understanding of how muscles get their power has been greatly expanded with new results published online July 10 in the Royal Society journal Proceedings of the Royal Society B. The Royal Society is the U.K.'s national academy of sciences. The basics of how a muscle generates power remain the same: Filaments ...

Daydreaming simulated by computer model

2013-07-12
Scientists have created a virtual model of the brain that daydreams like humans do. Researchers created the computer model based on the dynamics of brain cells and the many connections those cells make with their neighbors and with cells in other brain regions. They hope the model will help them understand why certain portions of the brain work together when a person daydreams or is mentally idle. This, in turn, may one day help doctors better diagnose and treat brain injuries. "We can give our model lesions like those we see in stroke or brain cancer, disabling groups ...

New theory uncovers cancer's deep evolutionary roots

2013-07-12
TEMPE, Ariz. -- A new way to look at cancer -- by tracing its deep evolutionary roots to the dawn of multicellularity more than a billion years ago -- has been proposed by Paul Davies of Arizona State University's Beyond Center for Fundamental Concepts in Science in collaboration with Charles Lineweaver of the Australian National University. If their theory is correct, it promises to transform the approach to cancer therapy, and to link the origin of cancer to the origin of life and the developmental processes of embryos. Davies and Lineweaver are both theoretical physicists ...

Artifact suppression and analysis of brain activities with EEG signals

2013-07-12
Electroencephalography is a test to measure the electrical activity of the brain generated by scalp surface after being picked up by metal electrodes and conductive media. Proper classification of electroencephalography data is the main task in electroencephalography based brain computer interface. Brain-computer interface is a communication system that connects the brain with computer (or other devices) but is not dependent on the normal output of the brain (i.e., peripheral nerve and muscle). Such interface transforms neural activities into signals to establish a new ...

Stress fracture risks may be modifiable

2013-07-12
CHICAGO, IL – Programs to improve movement patterns may help prevent stress fractures in athletes and military personnel, say researchers presenting their work today at the American Orthopaedic Society for Sports Medicine's Annual Meeting in Chicago, IL. "Several potentially modifiable muscular and biomechanical factors may be playing a part in the increased rates of stress fractures in athletes and military personnel," said Kenneth L. Cameron, PhD, MPH, ATC, lead author and Director of Orthopaedic Research at Keller Army Hospital, West Point, NY. "It's possible that ...

Shoulder surgery may make sense for young patients

2013-07-12
Arthroscopic bankart repair surgery is a cost-effective approach for patients suffering their first shoulder dislocation, according to research presented today at the American Orthopaedic Society for Sports Medicine's (AOSSM) Annual Meeting in Chicago, IL. "We based our conclusions on a Markov model, which takes into account how surgery affects the patient's recovery in relation to the actual costs of medical treatment," commented Ryan P. Donegan, MD, MS, from Dartmouth-Hitchcock Medical Center in Lebanon, NH. "For surgery to be cost-effective in this model, expenses ...

Corticosteroid injections may help injured NFL players return to play sooner

2013-07-12
CHICAGO, IL – Corticosteroid injections may speed-up the return time for National Football League (NFL) players suffering high ankle sprains, according to research presented today at the American Orthopaedic Society for Sports Medicine's Annual Meeting in Chicago, IL. Players treated with these injections typically returned 40% faster or approximately 10 days earlier than those not receiving the same treatment. "After examining players with stable high ankle sprains over an eight-year period, we discovered those treated with corticosteroid injections returned to play ...

Range of motion may be a predictor for elbow injuries in Major League Baseball pitchers

2013-07-12
CHICAGO, IL – Certain elements of a pitcher's throwing mechanics can increase the risk for elbow injuries, according to information presented by researchers at the American Orthopaedic Society for Sports Medicine's Annual Meeting today in Chicago, IL. The researchers examined 296 MLB pitchers throughout eight seasons from 2005-2012. Pitchers with a deficit of more than five degrees in total range of motion (TRM) in their dominant shoulder had a 2.3 times higher risk of injury, while pitchers with a deficit of five or more degrees in shoulder flexion of the dominant shoulder ...

LAST 30 PRESS RELEASES:

Resistance training may improve nerve health, slow aging process, study shows

Common and inexpensive medicine halves the risk of recurrence in patients with colorectal cancer

SwRI-built instruments to monitor, provide advanced warning of space weather events

Breakthrough advances sodium-based battery design

New targeted radiation therapy shows near-complete response in rare sarcoma patients

Does physical frailty contribute to dementia?

Soccer headers and brain health: Study finds changes within folds of the brain

Decoding plants’ language of light

UNC Greensboro study finds ticks carrying Lyme disease moving into western NC

New implant restores blood pressure balance after spinal cord injury

New York City's medical specialist advantage may be an illusion, new NYU Tandon research shows

Could a local anesthetic that doesn’t impair motor function be within reach?

1 in 8 Italian cetacean strandings show evidence of fishery interactions, with bottlenose and striped dolphins most commonly affected, according to analysis across four decades of data and more than 5

In the wild, chimpanzees likely ingest the equivalent of several alcoholic drinks every day

Warming of 2°C intensifies Arctic carbon sink but weakens Alpine sink, study finds

Bronze and Iron Age cultures in the Middle East were committed to wine production

Indian adolescents are mostly starting their periods at an earlier age than 25 years ago

Temporary medical centers in Gaza known as "Medical Points" (MPs) treat an average of 117 people daily with only about 7 staff per MP

Rates of alcohol-induced deaths among the general population nearly doubled from 1999 to 2024

PLOS One study: In adolescent lab animals exposed to cocaine, High-Intensity Interval Training boosts aversion to the drug

Scientists identify four ways our bodies respond to COVID-19 vaccines

Stronger together: A new fusion protein boosts cancer immunotherapy

Hidden brain waves as triggers for post-seizure wandering

Music training can help the brain focus

Researcher develop the first hydride ion prototype battery

MIT researchers find a more precise way to edit the genome

‘Teen’ pachycephalosaur butts into fossil record

Study finds cocoa extract supplement reduced key marker of inflammation and aging

Obesity treatment with bariatric surgery vs GLP-1 receptor agonists

Nicotinamide for skin cancer chemoprevention

[Press-News.org] NASA study shows disks don't need planets to make patterns