Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists Glimpse Exotic Matter in a Neutron Star

09.09.2004


The neutron star, left, is surrounded by a swirling disk of gas supplied by the companion star, the yellow-red sphere at right. The neutron star’s immense gravity pulls gas onto its surface. (Image credit: NASA/GSFC/Dana Berry)


Theory says that the neutron star crust is about a mile thick. Beneath is likely a superfluid of neutrons. Extreme gravity has compressed protons and electrons into neutrons. (Image credit: NASA/GSFC)


Scientists have obtained their best measurement yet of the size and contents of a neutron star, an ultra-dense object containing the strangest and rarest matter in the universe.

The measurement may lead to a better understanding of nature’s building blocks -- protons, neutrons and their constituent quarks -- as they are compressed inside the neutron star to a density trillions of times greater than on Earth.

Tod Strohmayer of NASA Goddard Space Flight Center in Greenbelt, Md., and Adam Villarreal, a physics graduate student at the University of Arizona, present their results today at the American Astronomical Society’s High Energy Astrophysics Division meeting in New Orleans.



Strohmayer and Villarreal estimate that the neutron star is about 1.8 times as massive as the sun -- slightly more massive than expected -- with a radius of about 7 miles (11.5 kilometers). It is part of a binary star system named EXO 0748-676, located about 30,000 light-years away in the southern sky constellation Volans, or Flying Fish.
The scientists used NASA Rossi X-ray Timing Explorer data to measure how fast the neutron star spins. Spin-rate was the unknown factor needed to estimate the neutron star’s size and total mass. Their results agree with a mass-to-radius ratio estimate made from European Space Agency (ESA) X-ray satellite observations in 2002.

The long-sought mass-radius ratio defines the neutron star’s internal density and pressure relationship, the so-called equation of state. "Astrophysicists have been trying for decades to constrain the equation of state of neutron star matter," Villarreal said. "Our results hold great promise for accomplishing this goal. It looks like equations of state which predict either very large or very small stars are nearly excluded."

Knowing a neutron star’s equation of state allows physicists to determine what kind of matter can exist within that star. Scientists need to understand such exotic matter to test theories describing the fundamental nature of matter and energy, and the strength of nuclear interactions. "We would really like to get our hands on the stuff at the center of a neutron star," said Strohmayer. "But since we can’t do that, this is about the next best thing. A neutron star is a cosmic laboratory and provides the only opportunity to see the effects of matter compressed to such a degree." A neutron star is the core remnant of a star once bigger than the sun. The interior contains matter under forces that perhaps existed at the moment of the Big Bang but which cannot be duplicated on Earth. In this system, gas from a "normal" companion star, attracted by gravity, plunges onto the neutron star. This triggers thermonuclear explosions on the neutron star surface that illuminate the region. Such bursts often reveal the spin rate of the neutron star through a flickering in the X-ray emission, called a burst oscillation.

Strohmayer and Villarreal detected a 45-hertz burst oscillation frequency, which corresponds to a neutron star spin rate of 45 times per second. This is a leisurely pace for neutron stars, which are often seen spinning at more than 600 times per second. They next capitalized on EXO 0748-676 observations with ESA’s XMM-Newton satellite, led by Jean Cottam of NASA Goddard in 2002. Cottam’s team detected spectral lines emitted by hot gas, lines resembling those of a cardiogram.

These lines had two features. First, they were Doppler shifted. This means the energy detected was an average of the light spinning around the neutron star, moving away from us and then towards us. Second, the lines were gravitationally redshifted. This means that gravity pulled on the light as it tried to escape the region, stealing a bit of its energy. The gravitational redshift measurement offered the first estimate of a mass-radius ratio, because the degree of redshifting depends on the mass and radius of the neutron star.

Strohmayer and Villarreal determined that the 45-hertz frequency and the observed line widths from Doppler shifting are consistent with a neutron star radius between 9.5 and 15 kilometers (between about 6 and 9 miles) with the best estimate at 11.5 kilometers (about 7 miles). They used the radius and the mass-radius ratio to calculate the neutron star’s mass between 1.5 and 2.3 solar masses, with the best estimate at around 1.8 solar masses.
credit: NASA/GSFC)

The result supports the theory that matter in the neutron star in EXO 0748-676 is packed so tightly that almost all protons and electrons are squeezed together to become neutrons, which swirl about as a superfluid, a liquid that flows without friction. Yet the matter isn’t packed so tightly that quarks are liberated, a so-called quark star. "Perhaps most exciting is that we now have an observational technique that should allow us to measure the mass-radius relations in other neutron stars," Villarrael said.

A proposed NASA mission called the Constellation X-ray Observatory would have the ability to make such measurements, but with much greater precision, for a number of neutron star systems.

Lori Stiles | EurekAlert!
Further information:
http://www.u.arizona.edu

More articles from Physics and Astronomy:

nachricht Witnessing turbulent motion in the atmosphere of a distant star
23.08.2017 | Max-Planck-Institut für Radioastronomie

nachricht Heating quantum matter: A novel view on topology
22.08.2017 | Université libre de Bruxelles

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>