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 behavior 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 polarized, and change in brightness. Investigating a new astronomical object is a bit like a detective job. This object was unique in that it started out invisible, became bright, faded away, and then reappeared. When we looked towards the center of our galaxy (the Milky Way), we found a source we called ASKAP J173608.2-321635 (this catchy name comes from its coordinates in the sky).
The past decade has seen thousands of transients discovered at optical and X-ray wavelengths, but radio wavelengths are largely untapped. Transients are usually connected with some of the most energetic and violent events in the Universe, such as the death of massive stars. That's why objects that do change (known as variables) or appear and disappear (known as transients) are so interesting. Most things astronomers see in outer space are fairly stable and don't change much on human time scales. We have been surveying the sky with ASKAP throughout 20 in search of unusual new objects, in a project called the Variables and Slow Transients (VAST) survey. Despite our best efforts, we are still unable to work out exactly what produced these mysterious radio waves.Ī strange signal from the heart of the Milky Way We first spotted the signal using the Australian Square Kilometre Array Pathfinder Telescope (ASKAP), then followed up with other telescopes around the world and in space. What's more, the radio waves in the signal had an uncommon "circular polarization," which means the electric field in the radio waves spirals around as the waves travel through space.
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