Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hotter than expected neutron star surfaces help explain superburst frequency

17.04.2007
A new theoretical thermometer built from heavy-duty mathematics and computer code suggests that the surfaces of certain neutron stars run significantly hotter than previously expected. Hot enough, in fact, to at least partially answer an open question in astrophysics -- how to explain the observed frequency of ultra-violent explosions known as superbursts that sometimes ignite on such stars' surfaces?

"This is the first model that goes into some reasonable detail about the nuclear physics that occur in the crusts of accreting neutron stars," said Hendrik Schatz, NSCL professor and co-author of a paper that will be published in The Astrophysical Journal in June. One of Schatz's co-authors, NSCL assistant professor Ed Brown, will present the results April 17 at a meeting of the American Physical Society in Jacksonville, Fla.

Superbursts emanate from binary systems in which a neutron star orbits a companion star. When the two stars get close enough together, a steady rain of material is sucked away from the companion star onto the surface of the neutron star.

Because a neutron star is so dense -- on Earth, one teaspoonful would weigh a billion tons -- the companion star material that reaches the neutron star surface is strongly compressed and heated. Eventually nuclear reactions trigger an explosion that burns through the surface layer of accumulated material, resulting in a burst of X-rays clearly detectable by ground- and space-based instruments.

X-ray bursts repeat every few hours to days, along the way fusing hydrogen and helium into a mixture of elements that is itself potentially reactive. In contrast, superbursts occur when, after many months, the accumulated "ashes" produced in the X-ray bursts ignite in a different, even more dramatic nuclear explosion.

The result is an outpouring of X-rays some 1,000 times as energetic as a standard X-ray burst. One superburst, which lasts only on the order of a few hours, releases as much energy as the sun will radiate in a decade.

Though hardly subtle astrophysical phenomena, superbursts remain shrouded in some mystery, largely because only twelve of the extreme events have ever been observed. This mystery is what attracted the attention of researchers participating in the Joint Institute for Nuclear Astrophysics, or JINA, project.

Working with colleagues at Los Alamos National Laboratory and the University of Mainz in Germany, JINA-affiliated NSCL scientists set out to build the most accurate model to-date of the crusts of accreting neutron stars. The team calculated that reactions in the stars' crusts release 10 times more heat than indicated by earlier models.

At least in part, this newly discovered heat helps to reconcile the work of theorists and experimentalists who study neutron stars. Prior to Schatz and Brown's research, theoretical astrophysicists predicted that superbursts should occur every ten years or so. Now, according to the new calculation, theorists can explain why the gigantic explosions should occur every three or four years.

But more work remains to be done. According to observational data, superbursts occur roughly annually -- and scientists still aren't altogether sure why.

"So this doesn't quite solve the problem," Brown said. "It's still an open question as to how nature ignites superbursts."

Geoff Koch | EurekAlert!
Further information:
http://www.nscl.msu.edu
http://arxiv.org/abs/astro-ph/0609828
http://www.jinaweb.org/docs/nuggets_07/schatz_sanjib.pdf

More articles from Physics and Astronomy:

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

nachricht Protecting the power grid: Advanced plasma switch for more efficient transmission
17.08.2018 | DOE/Princeton Plasma Physics Laboratory

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>