An international team of astronomers has made a precise measurement of a distant, spinning star that’s about a million times more precise than the previous world’s best. That resolution is like being able to see DNA’s double helix structure from the moon.
"Compared to other objects in space, neutron stars are tiny,” Jean-Pierre Macquart from Curtin University explains in a news release. They’re about tens of kilometers in diameter. “So we need extremely high resolution to observe them and understand their physics.” Neutron stars are particularly interesting for astronomers because some of them (called pulsars) gave off pulsed radio waves whose beams regularly sweep across telescopes. Nearly five decades since pulsars were discovered, astronomers still don’t understand how they emit those pulses.
To get this highest resolution yet, Macquart, Ue-Li Pen of the Canadian Institute of Theoretical Astrophysics, and colleagues used the interstellar medium -- the turbulent “empty” spaces in between, where charged particles float around -- as a giant magnifying glass to look at the radio waves emitted by a small, spinning neutron star called PSR 0834+06.
These pulse signals become distorted as they pass through the interstellar medium. The team was able to use the distortions to reconstruct a close-up view of the pulsar from thousands of individual images of the scattering speckle pattern.
"The best we could previously do was pointing a large number of radio telescopes across the world at the same pulsar, using the distance between the telescopes on Earth to get good resolution," Macquart explains. By combining views from several telescopes, the previous record had a resolution of 50 microarcseconds.
The new record using this “interstellar lens,” the galaxy's biggest telescope, is 50 picoarcseconds, or a million times more detail. And it resolves areas of less than 5 kilometers in the emission region. Because of that, the team found that the emission region of pulsar B0834+06 was much smaller than previously assumed and possibly much closer to the star's surface -- a critical piece of information for understanding the origin of the radio wave emission.
The work was published in Monthly Notices of the Royal Astronomical Society.
Image/video: Swinburne Astronomy Productions/CAASTRO