. 24/7 Space News .
Neutron Stars Warp Space-Time

Previous X-ray observatories detected iron lines around neutron stars, but they lacked the sensitivity to measure the shapes of the lines in detail.
by Staff Writers
Ann Arbor MI (SPX) Aug 30, 2007
Einstein's predicted distortion of space-time occurs around neutron stars, University of Michigan astronomers and others have observed. Using European and Japanese/NASA X-ray observatory satellites, teams of researchers have pioneered a groundbreaking technique for determining the properties of these ultradense objects.

Neutron stars contain the densest observable matter in the universe. They cram more than a sun's worth of material into a city-sized sphere, meaning a few cups of neutron-star stuff would outweigh Mount Everest. Astronomers use these collapsed stars as natural laboratories to study how tightly matter can be crammed under the most extreme pressures nature can offer.

Researchers who study neutron stars are seeking answers to fundamental physics questions. Their centers could hold exotic particles or states of matter that are impossible to create in a lab.

The first step in addressing these mysteries is to accurately and precisely measure the diameters and masses of neutron stars. A U-M study is one of two that have recently done just that.

Like neutron stars themselves, the region around these stars is also extreme. The motions of gas in this environment are described by Einstein's general theory of relativity. Scientists are now exploiting general relativity to study neutron stars.

U-M research fellow Edward Cackett and assistant professor Jon Miller are lead authors of a paper on the research that has been submitted to Astrophysical Journal Letters. Independent work reported by Sudip Bhattacharyya and Tod Strohmayer of NASA's Goddard Space Flight Center bolsters the results reported by Cackett and Miller, and together the results signal that an accessible new method for probing neutron stars has been found.

NASA describes the findings as "a big step forward."

Cackett and Miller used the Japanese/NASA Suzaku X-ray observatory satellite to survey three neutron-star binaries: Serpens X-1, GX 349+2, and 4U 1820-30. The team studied the spectral lines from hot iron atoms that are whirling around in a disk just beyond the neutron stars' surface at 40 percent light speed.

Previous X-ray observatories detected iron lines around neutron stars, but they lacked the sensitivity to measure the shapes of the lines in detail.

Cackett and Miller, along with the Goddard astronomers, were able to determine that the iron line is broadened asymmetrically by the gas's extreme velocity. The line is smeared and distorted because of the Doppler effect and beaming effects predicted by Einstein's special theory of relativity. The warping of space-time by the neutron star's powerful gravity, an effect of Einstein's general theory of relativity, shifts the neutron star's iron line to longer wavelengths.

The iron line Cackett and Miller observed in Serpens X-1 was nearly identical to the one Bhattacharyya and Strohmayer observed with a different satellite: the European Space Agency's XMM-Newton. In the other star systems, Cackett and Miller observed similarly-skewed iron lines.

"We're seeing the gas whipping around just outside the neutron star's surface," Cackett said. "And since the inner part of the disk obviously can't orbit any closer than the neutron star's surface, these measurements give us a maximum size of the neutron star's diameter. The neutron stars can be no larger than 18 to 20.5 miles across, results that agree with other types of measurements."

Knowing a neutron star's size and mass allows physicists to describe the "stiffness," or "equation of state," of matter packed inside these incredibly dense objects. Besides using these iron lines to test Einstein's general theory of relativity, astronomers can probe conditions in the inner part of a neutron star's accretion disk.

"Now that we've seen this relativistic iron line around three neutron stars, we have established a new technique," Miller said. "It's very difficult to measure the mass and diameter of a neutron star, so we need several techniques to work together to achieve that goal."

The paper authored by Cackett and Miller is titled, "Relativistic iron emission lines in neutron star low-mass x-ray binaries as probes of neutron star radii."

Community
Email This Article
Comment On This Article

Related Links
University of Michigan
Stellar Chemistry, The Universe And All Within It



Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


Water Vapor Seen 'Raining Down' On Young Star System
Los Angeles CA (SPX) Aug 30, 2007
NASA's Spitzer Space Telescope has detected enough water vapor to fill the oceans on Earth five times inside the collapsing nest of a forming star system. Astronomers say the water vapor is pouring down from the system's natal cloud and smacking into a dusty disk where planets are thought to form.







  • NASA debunks claims of drunken space flights
  • NASA's Troubled Future
  • NASA's Centennial Challenges To Advance Technologies
  • Science Teachers Take Flight In Zero-Gravity

  • HiRISE Confirms Existence of 'Pit Craters' On Mars
  • Threatening Conditions For Rovers In Giant Martian Dust Storm
  • Rovers Begin New Observations On Changing Martian Atmosphere
  • Calculating The Biomass Of Martian Soil

  • E'Prime Aerospace Corporation Selects First Launch Operations Facility
  • Sea Launch Awaits Delivery Of New Gas Deflector
  • India To Launch INSAT-4CR From Sriharikota On Sept 01
  • Lockheed Martin Marks 33rd Consecutive A2100 Success With The Launch Of BSAT-3A

  • European Hot Spots And Fires Identified From Space
  • China Develops Beidou Satellite Monitoring System
  • DigitalGlobe Announces Launch Date For WorldView-1
  • Radar reveals vast medieval Cambodian city: study

  • Outbound To The Outerplanets At 7 AU
  • Charon: An Ice Machine In The Ultimate Deep Freeze
  • New Horizons Slips Into Electronic Slumber
  • Nap Before You Sleep For Your Cruise Into The Abyss Of Outer Sol

  • Shrinking Giants, Exploding Dwarves
  • Water Vapor Seen 'Raining Down' On Young Star System
  • Neutron Stars Warp Space-Time
  • XMM-Newton And Suzaku Help Pioneer Method For Probing Exotic Matter

  • An Exploding Lunar Eclipse
  • SpaceDev To Build Lunar Lander Prototype
  • Drawing A Living On Lunar
  • SMART-1 Diagnoses Wrinkles And Excess Weight On The Moon

  • Lockheed Martin Bids On Next Generation Global Positioning Satellite System
  • Boeing Bids On Next Generation Global Positioning Satellite System
  • Tracking The Elusive Shipping Container Out Beyond The Horizon
  • Russia Starts Serial Production Of New Navigation Systems

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement