Astronomers discover dead star cloaked by interstellar dust as they capture a spectacular view of the center of the Milky Way
Invisible to ordinary telescopes, objects in the center of our Milky Way galaxy, have intrigued astronomers for many decades. Now, armed with a powerful radio telescope, Australian astronomers have discovered remains of dead stars -- that have been hiding behind a cloak of interstellar dust, until now.
The new set of images released by scientists from the International Centre for Radio Astronomy Research (ICRAR) shows a new view of the Milky Way (Image by Dr. Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team). "Our images are looking directly at the middle of the Milky Way, towards a region astronomers call the Galactic Center,'' says astrophysicist Dr Natasha Hurley-Walker, from the Curtin University node of the ICAR. She adds, “This is really exciting for us because it's hard to find supernova remnants in this phase of life -- they allow us to look further back in time in the Milky Way.”
The galactic center is covered in interstellar dust, keeping the objects in them hidden. To view past the dust, scientists rely on telescopes that see objects in radio light or infrared light, for instance. Earlier last month, using their Spitzer Space Telescope's infrared cameras, NASA released an image of the crowded galactic center.
In this study, the scientists use the Murchison Widefield Array (MWA) telescope, whose images show what our galaxy would look like if human eyes could see radio waves.
The MWA can capture supernova remains that are older, further away, or in very empty environments -- a feat that has been a challenge, so far. Earlier instruments have easily spotted younger and closer remains, of which 295 are already known, according to the study.
Analyzing images from MWA, Dr Hurley-Walker and team discovered the leftovers of 27 massive stars that exploded in supernovae at the end of their lives. The authors add that these stars would have been eight or more times more massive than the sun. The radio images trace the edges of the explosions as they continue their ongoing expansion into interstellar space. Some are huge, larger than the full moon, and others are small and hard to spot in the complexity of the Milky Way.
Of the newly-discovered supernova remains, Dr Hurley-Walker said one of them lies in an empty region of space, far out of the plane of our galaxy, and is quite young and extremely faint. "It is the remains of a star that died less than 9,000 years ago, meaning the explosion could have been visible to Indigenous people across Australia at that time," she says.
Further, the team found two unusual remnants. Dubbing them "orphans”, the scientists found them in a region of the sky where there are no massive stars. Other supernova remnants discovered in the research are very old, she adds.
For all its advantages, MWA has its shortcomings too. The MWA is limited in its sensitivity and resolution, says Dr Hurley-Walker. Astronomers have their hopes pinned on the world's largest radio telescope, the Square Kilometre Array, which is due to be built in Australia and South Africa from 2021.
Another telescope is in the pipeline. NASA's James Webb Space Telescope (JWST) is expected to open its powerful infrared eyes in 2021 to capture images of the galactic center in finer detail. Such images, according to NASA, could provide answer questions on the origin of our galaxy and how it evolves over time.