An object very close to us
This strange object is located 4000 light-years from Earth. But when one considers that a light year corresponds to the distance that light has traveled in a vacuum in a year, that is, more or less 9461 billion kilometers, it is easy to realize that this object is located more than 37 billiards away miles from home. These values seem colossal, and yet, on the scale of the universe, it is as if it is right next to us.
The mysterious object was discovered thanks to the Murchinson Widefield Array (MWA) telescope located in Western Australia. MWA is the first element in a much larger set called the Square Kilometer Array (SKA), which should soon see the light of day. This is a giant radio telescope project consisting of a set of interferometers capable of working in meter and centimeter wavelengths. It will be primarily installed in Australia and South Africa.
MWA is a low-frequency radio telescope used to study the origin of the universe, the formation of stars and galaxies, or the search for extraterrestrial life. It consists of 512 tiles forming a set of more than 8000 double-polarized dipole antennas operating in a frequency range from 70 to 300 MHz. These antennas are spread over an area of 1.5 km
which makes it possible to form a network that allows a very high image quality.
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Impossible electromagnetic radiation
This object produces intense electromagnetic radiation every 18.18. minute. Such phenomena with regular wave and radiation emissions are common in the universe, but this frequency has never been seen before.
Pulsars are, for example, neutron stars that rotate very fast and emit rays of electromagnetic radiation periodically into space. Quite often, pulsars ‘turn on’ and ‘turn off’ over very short periods, ranging from a few seconds to a few milliseconds. These are rapid transient phenomena. Other objects, such as supernovae, are slow transients that occur in days and disappear in months.
Astronomers from the International Center for Radio Astronomy Research in Australia also noted that this object is intensely bright and has a very strong magnetic field.
For scientists, there is still a mystery. By doing all the calculations, they realized that this object should not have enough current to produce this electromagnetic radiation every 18.18. minute. But it turns out that it generates this huge release of energy three times an hour. Scientists know nothing similar in the universe!
The signal was observed at a wide range of frequencies. This means that it is a natural phenomenon. It is therefore not sent on purpose of any kind of life. For Australian scientists, this event could be an ultra-long period magnetar. This phenomenon is known theoretically but has never been observed.
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The magnetar, a very dense neutron star
The magnetar is a very rare type of neutron star that produces very high energy electromagnetic radiation such as X-rays and gamma rays. These rays produce a very intense magnetic field that is 1000 times stronger than that of a classical neutron star.
At the end of its life, when a massive star collapses on its own in a supernova explosion, it can either become a neutron star or a black hole. Magnets are actually quite rare forms of neutron stars, as scientists estimate that every tenth supernova would form a magnetar on average.
Regarding the formation of magnetars, astronomers give the following explanation: right after the collapse of the massive star, the formed neutron star cools very quickly by rejecting a huge amount of neutrinos and begins to rotate very rapidly about itself. This rapid drop in temperature creates a convective motion inside the star. These brutal movements of matter in the star produce a sudden and very sharp rise in the magnetic field. In fact, it is the normally existing dynamo effect that is greatly amplified. This gain can in some cases go up to 10
Astronomers now want to continue their studies to search for and discover, perhaps, other strange objects in the Milky Way. They will then be able to verify whether the observation they have just made is a unique case or whether it is the first member of a new category of objects in our universe.
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Repeating Transient Animation from ICRAR on Vimeo.
Source: Hurley-Walker, N., Zhang, X., Bahramian, A. et al. “A radio transient with an unusually slow periodic emission”, Nature, 601, 526 –530 (2022), https://doi.org/10.1038/s41586-021-04272-x