Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars

March 21, 2017, International Centre for Radio Astronomy Research
A schematic view of a pulsar. The sphere in the middle represents the neutron star, the curves indicate the magnetic field lines and the protruding cones represent the emission zones. Credit: Mysid

What sounds like a stomach-turning ride at an amusement park might hold the key to unravelling the mysterious mechanism that causes beams of radio waves to shoot out from pulsars—super-magnetic rotating stars in our Galaxy.

New research from Curtin University, obtained using the Murchison Widefield Array (MWA) located in the Western Australian outback, suggests the answer could lie in a 'drifting carousel' found in a special class of pulsars.

Curtin PhD student Sam McSweeney, who led the research as part of his PhD project with the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO) and the International Centre for Radio Astronomy Research (ICRAR), described pulsars as extremely dense neutron stars that emit beams of .

"These pulsars weigh about half a million times the mass of the Earth but are only 20km across," Mr McSweeney said.

"They are nicknamed 'lighthouses in space' because they appear to 'pulse' once per rotation period, and their sweeping light signal can be seen through telescopes at exceptionally regular intervals."

Thousands of pulsars have been seen since their first discovery in the late 1960s, but questions still remain as to why these stars emit radio beams in the first place, and what type of model best describes the radio waves, or 'light', that we see.

Antenna 'tiles' of the Murchison Widefield Array (MWA) are in the Western Australian desert. Credit: MWA Project / Curtin University
"The classical pulsar model pictures the emission that is shooting out from the magnetic poles of the pulsar as a light cone," Mr McSweeney said.

"But the signal that we observe with our telescopes suggests a much more complex structure behind this emission - probably coming from several emission regions, not just one."

The 'drifting carousel' model manages to explain this complexity much better, describing the emission as coming from patches of charged particles, arranged in a rotating ring around magnetic field lines, or a carousel.

"As each patch releases radiation, the rotation generates a small drift in the observed signal of these sub-pulses that we can detect using the MWA," Mr McSweeney said.

"Occasionally, we find that this sub-pulse carousel gets faster and then slower again, which can be our best window into the plasma physics underlying the pulsar emission."

One possibility the researchers are currently testing is that surface temperature is responsible for the carousel changing rotation speed: localised 'hotspots' on the pulsar surface might cause it to speed up.

"We will observe individual pulses from these drifting pulsars across a wide range of radio frequencies, with lower frequency data than ever before," Mr McSweeney said.

"Looking at the same with different telescopes simultaneously will allow us to trace the emission at different heights above their surface."

The researchers plan to combine the data from the MWA, the Giant Metre-wave Radio Telescope in India and the CSIRO Parkes Radio Telescope in New South Wales to - literally - get to the bottom of the mysterious pulses.

A paper explaining the research "Low Frequency Observations of the Subpulse Drifter PSR J0034-0721 with the Murchison Widefield Array" was recently published in The Astrophysical Journal.

Explore further: Astronomers harness the galaxy's biggest telescope to make most precise measurement of spinning star

More information: S. J. McSweeney et al. Low-frequency Observations of the Subpulse Drifter PSR J0034−0721 with the Murchison Widefield Array, The Astrophysical Journal (2017). DOI: 10.3847/1538-4357/aa5c35

Related Stories

The mystery of part-time pulsars

January 5, 2017

A new discovery has upended the widely held view that all pulsars are orderly ticking clocks of the universe. A survey done at the Arecibo Observatory in Puerto Rico has fortuitously discovered two extremely strange pulsars ...

Chameleon pulsar baffles astronomers

January 24, 2013

A pulsar that is able, without warning, to dramatically change the way in which it shines has been identified by an international team of astronomers.

Pulsars in many octaves

April 22, 2010

A unique combination of telescopes allowed astronomers to simultaneously observe the radio wavelength light from six different pulsars across wavelengths from only 3.5 centimetres up to 7 metres - a difference-factor of 200, ...

Parkes telescope finds new kind of star

February 16, 2006

An international team of astronomers using CSIRO’s Parkes radio telescope in eastern Australia has found a new kind of cosmic object.

Recommended for you

The powerful meteor that no one saw (except satellites)

March 19, 2019

At precisely 11:48 am on December 18, 2018, a large space rock heading straight for Earth at a speed of 19 miles per second exploded into a vast ball of fire as it entered the atmosphere, 15.9 miles above the Bering Sea.

OSIRIS-REx reveals asteroid Bennu has big surprises

March 19, 2019

A NASA spacecraft that will return a sample of a near-Earth asteroid named Bennu to Earth in 2023 made the first-ever close-up observations of particle plumes erupting from an asteroid's surface. Bennu also revealed itself ...

Nanoscale Lamb wave-driven motors in nonliquid environments

March 19, 2019

Light driven movement is challenging in nonliquid environments as micro-sized objects can experience strong dry adhesion to contact surfaces and resist movement. In a recent study, Jinsheng Lu and co-workers at the College ...

Revealing the rules behind virus scaffold construction

March 19, 2019

A team of researchers including Northwestern Engineering faculty has expanded the understanding of how virus shells self-assemble, an important step toward developing techniques that use viruses as vehicles to deliver targeted ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.