What can we say about what it actually is?Ĭan it be a star? It seems unlikely because stars also emit much of their light in the optical and infrared (like the Sun), but we detect nothing at these wavelengths.Ĭan it be a pulsar? Like our signal, pulsars produce polarised radio waves and can vary dramatically in brightness. We have observed this strange object at multiple wavelengths using telescopes on three continents and in space. Telescopes working at other wavelengths can serve as another pair of eyes to help us find new clues.Īfter the MeerKAT detection, we searched for the source in X-rays (using the space-based Neil Gehrels Swift Observatory and Chandra X-ray Observatory) and infrared (using the Gemini telescope in Chile). It is always a good idea to investigate from multiple perspectives. Radio lightcurve showing how ASKAP J173608.2-321635 varies with time. The source disappeared in the course of a single day, even though it had lasted for weeks in our previous ASKAP observations. Luckily, the signal returned, but the behaviour of the source was now dramatically different. Because the signal was intermittent, we observed it for 15 minutes every few weeks, hoping we would see it again.
We then tried the more sensitive MeerKAT radio telescope in South Africa. However, these observations yielded nothing. We next observed the source with the Parkes radio telescope in New South Wales to decide whether it was a pulsar. We need evidence to determine what it is.īased on our ASKAP data, we thought the new object might be a pulsar or a flaring star: both types of object can be polarised, and change in brightness. Investigating a new astronomical object is a bit like a detective job. Almost all of them are sources we understand well, such as pulsars (the rapidly rotating, highly magnetised remnants of exploded stars) or highly magnetised red dwarf stars. Polarised radio sources are extremely rare: we might find fewer than ten circularly polarised sources out of thousands.
Our eyes cannot distinguish between polarised and unpolarised light, but ASKAP has the equivalent of polaroid sunglasses for radio waves. Author providedĪs well as changing over time, the signal was circularly polarised. The small insets show the source turning off and on in images from the MeerKAT telescope. ASKAP image of the Galactic Centre region.
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