Astronomers have known for a while that our galaxy is full of many more remains of supernovas than we’ve been able to detect. This has all changed with a new radio telescope collaboration which has revealed around 20 previously unseen remnants of dying stars.
Remnants of stars are exploding clouds of gas, marking the last stage of a star’s life cycle after it explodes in a supernova. Astronomers estimate that a star in the Milky Way explodes as a supernova at least once every 100 years.
Essentially, this explosion is a way for massive stars to exhaust the last of their fuel; the stars have the potential to eject clouds of gas and dust many light years away from the point of the explosion. The remnants can linger for thousands of years before dispersing.
So far, astronomers have found hundreds of similar remnants across the Milky Way, but they estimate that they’ve only detected around 20% of the total number. They know this because researchers found ‘thin tendrils and clumpy clouds’ in the areas between numerous stars in the Milky Way, which suggests that there are more supernova remnants than previously observed.
Usually, these remnants are discovered by detecting radio emissions that come from them as they expand; these emissions reveal their previously undetectable shapes, but unfortunately, many are too faint to be picked up by current technology. Astronomers know how many we should be seeing but can only detect around one-fifth.
Recently, this all changed. PhD student Brianna Ball from the University of Alberta and her supervisor, Roland Kothes, facilitated a collaboration between two different radio telescope projects. On the 16th of January of this year, their project revealed a new way of observing supernova remnants.
They combined the powers of two different projects.
First, the Australian Square Kilometre Array Pathfinder (ASKAP), a radio telescope made up of 36 relatively small dishes (each 12 metres wide), which mimic a single large telescope with a 6km wide dish). This telescope has a good resolution but can’t detect radio emissions from even the largest star regions. Therefore, its power was combined with the Parkes/Murriyang telescope, one of the world’s largest single-dish radio telescopes, allowing novel detection.
By combining maps of our galaxy from each telescope, supernova remnants in the Milky Way were revealed with ‘extremely high precision and accuracy’. The team uncovered 21 supernova remnants, of which only seven were previously known.
The resulting image is being referred to by scientists as the most detailed radio image of our galaxy so far, showing the galactic plane in its ‘finest detail yet’. The colour in the image represents heat – purple is the coolest, then blue, green, red, and finally, the hottest areas are white.
The image contains five of the 21 newly revealed remnants, including one shaped with a figure of eight. The picture was taken along the Norma Arm in the Milky Way, which is near the dense Galactic Centre, where dust and gas heavily obscure light.
Through this approach of generating high-quality images of the sky, astronomers hope to further their understanding of our galaxy and beyond with future observations. It’s estimated that there might be around 1500 more undiscovered supernova remnants in our galaxy.
By finding and studying new remnants, scientists can learn more about the kinds of stars that explode as supernovas. Furthermore, they can reveal useful information about the Milky Way, as the remnants often contain heavy elements which are the building blocks of other stars, planets, and even life itself.