MWA: From the Outback to the Cosmos

Way out in the wilds of Western Australia is a major astronomy facility that doesn’t look at all like a telescope. The Murchison Widefield Array is a radio telescope that observes the cosmos at frequencies between 70 to 300 MHz. It looks like a bunch of funny little metal scaffolds connected by wires. However, in recent years, since its first deployment in 2013, it has been finding amazing things in our galaxy.

How do I know all this? I worked on a video about the array for MIT Haystack Observatory (which has a page dedicated to the project.) I’ve also written about it previously and even did a podcast about it. The observatory was involved in some of the preliminary design and testing work for the MWA. I wrote and produced it along with my partner, M. C. Petersen, with some valuable cooperation from MIT and some of its contractors. Here’s a link to the video.

MWA’s Latest Discovery

Here we are, ten years later, and MWA is doing exactly what Dr. Colin Lonsdale, the director at Haystack, said it would do in the video: searching out low-frequency activities in the cosmos. The latest work is a low-frequency view of the center of our galaxy as it would appear to us if we could sense light at the same frequencies as MWA does. In the image, scientists have assigned colors to different ranges of light that MWA detected. The red indicates the lowest frequencies, while the green shows the mid-range, and the blue areas are the highest-frequency light. The filmy filaments that seem to float out of the plane of the galaxy are clumps of gas spiraling around the magnetic fields embedded in our galaxy.

Finding Dying Stars with MWA

The image also revealed 27 supernova remnants that had not been observed previously. Those are the leftovers of supermassive stars that blew themselves apart and scattered their remains to space. The radio images from MWA show the shapes of the remnants. Some of these remnants were hard to spot against the busy backdrop of our galaxy. That didn’t stop the MWA from detecting them in its survey of the Milky Way. That ongoing work called the Galactic and Extragalactic All-sky MWA (GLEAM) survey. The current image from GLEAM has centered on the core of the galaxy and then worked its way out. Each scan finds low-frequency activity and hidden stellar objects. You can read more about the image and the scientists behind it here.

The survey is mapping the galaxy at between 72 and 231 MHz. From its very radio-quiet area in the Australian Outback, the MWA benefits from the LACK of radio frequency interference. That includes TV and FM radio, which permeates airwaves elsewhere. That’s one of the main reasons MWA is out there. It’s largely sheltered from human radio noise interference that could ruin its observations.

MWA and the Supernovae Remnants

The supernova remnants that MWA found are older ones. Studying them gives astronomers a great look back to more ancient activities in our galaxy. Younger supernova remnants are bright in both optical and radio regimes, while older ones look dim. That makes them tougher to spot. So, the MWA, which is a predecessor instrument to the low-frequency Square Kilometer Array, is proving to be a pathfinder in many ways. The low-frequency universe it “sees” is the latest area of study for radio astronomers. I look forward to seeing more from this odd little array that is proving itself to be a big contributor to science.

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