In the cosmos, some objects emit pulses rather than a continuous light. This year, astronomers discovered Askap J1832, an object on the Milky Way which emits both X -rays and radio waves, and which is unknown to anything.
In a study published in Nature In May, we report the discovery of a new transitional phenomenon at a long time – and, for the first time, which also regularly emits X -ray starts.
The long -term transients are a class of recently identified cosmic objects which emit intense radio wave flashes every few minutes, or even several hours apart, which is much longer than the very fast pulsed emissions that we generally detect in pulsars, which come from the explosion of a massive star at the end of life.
The nature of these long -term transitional objects and the way in which they generate their unusual signals remain a mystery.
Our discovery opens a new window on the study of these enigmatic sources. But it also strengthens the mystery: the object that we have found does not look like any type of star or system known in our galaxy or beyond.
Supplied by the author
On the lookout for radio flickering in the sky
The night sky has many elements invisible to the naked eye, but detectable to other wavelengths, such as radio waves.
Our research team regularly scrutinizes the radio sky using the Australian Ska Pathfinder (Askap), operated by the CSIRO in the Wajarri Yamaji region, in western Australia. Our goal is to find cosmic objects that appear and disappear – which are called ” transients “In English,” transitional objects “, in French.
Transitional objects are often linked to some of the most powerful and spectacular events in the universe, such as the explosive death of stars.
At the end of 2023, we spotted an extremely brilliant source, called Askap J1832-0911 (according to his position in the sky), in the plane of our galaxy. This object is located at around 15,000 light years … it’s far away, but still on the Milky Way.
CSIRO
A spectacular event
After the initial discovery, we started monitoring observations using telescopes located around the world in the hope of capturing other pulses. Thanks to continuous surveillance, we found that the radio pulses from Askap J1832 arrived regularly, every forty-four minutes. This confirmed that it was a new member of the little -supplied group of long -term transients.
We also searched the old data from the same part of the sky, but we did not find any trace of the object before its discovery in 2023. This suggests that a spectacular event occurred shortly before our first detection, an event sufficiently powerful to “light” our atypical transitional object suddenly.
Then, in February 2024, Askap J1832 became extremely active. After a calm period in January, the source was considerably intensified: less than 30 objects in the sky have never reached such brightness in the radio field … By way of comparison, most of the stars that we detect on radio are about 10,000 times less bright than Askap J1832 during this outbreak.
A stroke of luck
X -rays are a form of light that we cannot see with our eyes. They generally come from extremely hot and energetic environments. Although a dozen similar objects emitting radio waves (those we have initially detected) have been discovered to date, no one had ever observed an X broadcast on their part.
In March, we tried to observe Askap J1832 on X -rays. However, due to technical problems with the telescope, the observation could not take place.
Then luck! In June, I contacted my friend Tong Bao, a postdoctoral researcher at the Italian National Institute of Astrophysics, to check if previous observations on X -rays had captured the source. To our surprise, we have found two previous observations from the NASA X -ray -ray -ray observatory, although the data is still in a limited dissemination period (and therefore not yet made public outside a limited circle of researchers).
We contacted Kaya Mori, researcher at Columbia University and responsible for these observations. He generously shared the data with us. To our surprise, we discovered light X signals from Askap J1832. Even more remarkable: X -rays followed the same 44 -minute cycle as the radio pulses.
It was a real luck. Chandra was pointed out towards a completely different target, but out of pure coincidence, he captured Askap J1832 during his unusual and active phase.
Such a fortuitous alignment is extremely rare, it is like finding a needle in a cosmic hay boot.
NASA/CXC & J. Vaughan
Always a mystery
The simultaneous presence of radio emissions and X starts is a common characteristic of dead stars with extremely powerful magnetic fields, such as neutron stars (large -mass dead stars) and white dwarfs (low -mass dead stars).
Our discovery suggests that at least certain long -term transitional objects could come from this type of stellar vestiges.
But Askap J1832 does not correspond to any object category known in our galaxy. His behavior, although similar in certain respects, remains atypical.
We need more observations to really understand what’s going on. It is possible that ASKAP J1832 is of an entirely new nature for us, or that it issues radio waves in a way that we have never observed before.
