The intriguing cosmic mystery of Fast Radio Bursts (FRBs) sheds light (pun intended) on another mystery. By studying FRB signatures from nearby galaxies, astronomers have discovered that the Milky Way has far less matter than expected.
Fed is exactly what the name suggests. They are bursts of radio signals lasting only milliseconds from deep space. Some are one-hit wonders, others are random or regularly repeated. The exact cause remains unknown, but with hundreds recorded since the first detection in 2007, we are getting closer to answering each event.
For the new study, astronomers looked at FRB, first detected in March 2022 by California’s Deep Synoptic Array (DSA). It was back in a galaxy about 163 million light-years away, and knowing that distance and the direction it came from, the team was able to measure how much the signal dispersed before reaching the observatory. This allows astronomers to see how much matter the radio signal has passed through on its journey.
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In doing so, the researchers were able to calculate how much matter there is in the Milky Way’s ambient medium (CGM) — the halo of dust and gas that surrounds our entire galaxy. It’s like shining a light through fog to figure out how thick it is, he explains.
From this, scientists calculated that the mass of the Milky Way’s CGM is less than 100 billion of the Sun. This is much lighter than expected. In fact, when combined with all of the rest of the galaxy’s normal matter, the Milky Way’s total mass is less than 60% of his average galaxy.
So where is the problem? The team says this new evidence supports previous hypotheses that matter is often blown out of galaxies thanks to various processes such as stellar winds, supernovae and supermassive black holes.
“These results strongly support the scenario predicted by galaxy-formation simulations, in which feedback processes expel matter from the galaxy’s halo,” said Vikram Ravi, lead author of the study. “This is fundamental to galaxy formation, and matter periodically flows into and is blown out of the galaxy.”
New insights are inevitable as DSA is set to become even more powerful. Currently, only 63 of the final 110 dishes are operational, and in the long term, 2,000 dishes will constitute the follow-up observatory. This will allow us to detect far more FRBs, better answering mysteries and other discoveries like this new revelation about the Milky Way.
The study has been submitted for publication astrophysics journal.
Source: California Institute of Technology
