Three articles published in the journal “Publications of the Astronomical Society of Australia (PASA)” – availabe here, here and here (links to PDF files) – report some results of the GaLactic and Extragalactic All-sky MWA (GLEAM) survey. A team of researchers created some images obtained thanks to the Murchison Widefield Array (MWA) radio telescope showing the center of the Milky Way. Thanks to the low-frequency radio emissions detected, it was possible to generate an image that reproduces both the larger structures and the details. This means that it was possible to obtain an overall image and images of individual objects such as 27 supernova remnants.
The MWA radio telescope is a precursor of the Square Kilometer Array (SKA), the next generation radio telescope, and aims to develop the technologies needed to build it. For the various precursor projects, this also means doing high-level scientific research, for the MWA among other things it meant conducting the GLEAM survey, started in August 2013 for the first year, continued for a second year and subsequently completed with a third year up to July 2016.
The data collected during the GLEAM survey were used in various ways, in this case astrophysicist Natasha Hurley-Walker of the Curtin University node of the International Center for Radio Astronomy Research (ICRAR) directed the creation of images at the Pawsey Perth Supercomputing Center putting together data about the center of the Milky Way.
The top image (Courtesy of Dr. Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team. All rights reserved) shows the center of the Milky Way with lower radio frequencies in red, medium frequencies in green and higher ones in blue. The huge golden filaments indicate huge magnetic fields. Supernova remnants are visible as small bubbles and massive star-forming regions are shown in blue. The supermassive black hole at the center of the Milky Way is hidden in the bright white region at the center.
The researchers were able to find in the images the remnants of 27 supernovae, visible in the bottom image (Courtesy Dr. Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team. All rights reserved) in their different shapes and sizes. Radio frequency images show the edges of the explosions as their remnants keep on expanding into interstellar space.
Generally the remnants of supernovae that are relatively recent and near or in dense environments are discovered, thanks to the MWA radio telescope it was possible to discover the remnants of supernovae that are older, more distant or in empty environments. One of the 27 discoveries is quite recent as it dates back less than 9,000 years ago but is very dim because the progenitor star was in a really empty region of space, far from the galactic plane.
This is an excellent result for the MWA radio telescope and it’s only the beginning because the SKA radio telescope will have a sensitivity thousands of times higher and a much better resolution. For example, astronomers expect to find remnants of supernovae even on the other side of the Milky Way. It’s just one of the results that will be possible in the next decade thanks to SKA.