Page 19 - EngineerIT June 2022

SPACE SCIENCES

Strange neutron star spinning

every 76 seconds is discovered in

stellar graveyard

n international team of scientists Artist’s impression of the 76s
has discovered a strange radio pulsar (in magenta) compared
Aemitting neutron star which to other, more rapidly
rotates extremely slowly, completing one spinning sources. (c) Danielle
Futselaar (artsource.nl)
rotation every 76 seconds.
The team, led by members of the
ERC-funded MeerTRAP (More Transients
and Pulsars) group at the University of
Manchester, says it is a unique discovery as it
resides in the neutron star graveyard where
they do not expect to see any radio emission
at all. The discovery was made using the
MeerKAT radio telescope in South Africa.
The source was initially found from
a single flash or pulse, by the MeerTRAP
instrument whilst piggybacking on imaging
observations being led by a different team, important implications for how neutron stars are born and age.”
ThunderKAT. MeerTRAP and ThunderKAT “The majority of pulsar surveys do not search for periods this long and so we have no
then worked closely together to work out idea how many of these sources there might be. In this case, the source was bright enough
its origin. Combining the data from the that we could detect the single pulses with the MeerTRAP instrument at MeerKAT.”
two teams, it was then possible to confirm The newly discovered neutron star is named PSR J0901-4046, and shows characteristics
the pulsations and get an accurate position of pulsars, (ultra-long period) magnetars and even fast radio bursts. While the radio energy
for the source, enabling detailed and more produced suggests a pulsar origin, the pulses with chaotic sub-pulse components, and the
sensitive follow-up observations. polarization of the pulses, are reminiscent of magnetars.
Neutron stars are extremely dense While the spin period of PSR J0901−4046 might be more consistent with a white dwarf,
remnants of a supernova explosion of a another less extreme type of stellar remnant, scientists do not see any multi-wavelength
massive star. They can produce beams support for this. It is presently unclear how long this source has been emitting in the radio. It
of radio waves which sweep around the was discovered in a well-studied part of the galaxy, but radio surveys don’t usually search for
sky as the neutron star spins, producing periods this long, or pulses that last more than a few tens of milliseconds.
regular flashes like cosmic lighthouses. “The radio emission from this neutron star is unlike any we have ever seen before,”
Scientists currently know of about 3000 of explained Professor Ben Stappers at the University of Manchester, and principal investigator
these in our own galaxy. However, the new of the MeerTRAP project. “We get to view it for about 300 milliseconds, which is much
discovery is unlike anything seen so far. The longer than for the majority of other radio emitting neutron stars. There seem to be at least
team thinks it could belong to the theorised seven different pulse types, some of which show strongly periodic structure, which could be
class of ultra-long period magnetars with interpreted as seismic vibrations of the neutron star. These pulses might be giving us vital
extremely strong magnetic fields. insight into the nature of the emission mechanism for these sources.”
Dr Manisha Caleb, formerly from the “The sensitivity that MeerKAT provides, combined with the sophisticated searching that
University of Manchester and now at the was possible with MeerTRAP and an ability to make simultaneous images of the sky, made
University of Sydney, who led the research this discovery possible. Even then it took an eagle eye to recognise it for something that was
said: “Amazingly we only detect radio possibly a real source because it was so unusual looking!” said Dr Ian Heywood from the
emission from this source for 0.5% of its ThunderKAT team and the University of Oxford, who collaborated on this study.
rotation period. This means that it is very Detecting similar sources is observationally challenging, which implies that there may
fortuitous that the radio beam intersected be a larger undetected population waiting to be uncovered. This new discovery adds to the
with the Earth. It is therefore likely that possibility of the existence of a new class of radio transients, the ultra-long period neutron
there are many more of these very slowly stars, suggesting a possible connection to the evolution of highly magnetised neutron stars,
spinning sources in the galaxy which has ultra-long period magnetars, and fast radio bursts. n

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