Astronomers have detected unexpected behavior in fast radio bursts (FRBs) – mysterious signals from deep space – that is shaking up theories about their origin.
Repeating Radio Bursts Reveal Surprises
FRBs are intense pulses of radio waves that appear temporarily and come from far beyond our galaxy. Most burst just once, but a small share emit repeat bursts. New observations of repeating FRB 121102, first detected in 2012, show its radio emissions are more complex than thought [based on https://phys.org/news/2023-12-secrets-fast-radio-pieces-puzzle.html].
The odd FRB gets dimmer and brighter in a way never seen before. “It was phenomenal to find FRB 121102 bursting in this way every hour. Bursts were either bright or weak, but rarely at an intermediate level,” said Dr. Ziggy Pleunis, a team member at McGill University in Canada [https://www.albanyherald.com/news/mysterious-fast-radio-bursts-in-space-keep-getting-stranger/article_7b869e4a-f86b-5085-94d0-009e8e849d90.html].
| Flux Density | Number of Bursts |
|---|---|
| Bright | 156 |
| Dim | 72 |
The changes suggest FRB 121102 comes from a young and highly magnetized neutron star. “The diversity in fast radio bursts is increasing very quickly. I expect we’ll have more surprises in store soon,” said Dr. Shriharsh Tendulkar at McGill [https://phys.org/news/2023-12-secrets-fast-radio-pieces-puzzle.html].
Clues Point to Star’s Environment
FRB 121102 was first spotted inside a dwarf galaxy over 3 billion light years away. Unlike most one-off FRBs from distant galaxies, this one churns repeatedly [https://amp.cnn.com/cnn/2023/12/14/world/repeating-fast-radio-burst-quirk-scn/index.html].
Of the over 500 FRBs detected, only about 10% have repeated. What makes FRB 121102 special lies in its home. “It comes from a turbulent environment, likely near the supermassive black hole at the galaxy’s core. Material swirling around the black hole powers unusual outflows,” explained Dr. Daniele Michilli at MIT [https://ras.ac.uk/news-and-press/news/never-seen-fast-radio-burst-sheds-new-light-deep-space-signals].
This extreme setting likely explains the odd variable brightness. Astronomers think blobs of material moving near its source occasionally block parts of the bursts.
“This galaxy has all the right characteristics to produce repeating fast radio bursts. Finding more objects like it will be key to understanding the physical nature and diversity of FRBs,” added Dr. Michilli.
Next Steps Toward Solving the Mystery
While the new observations don’t completely solve the mystery, astronomers are thrilled with the clues. “FRB 121102 continues to surprise us. The next step is to comb through the Signals database and see if other repeating FRBs behave this way,” said Dr. Tendulkar [https://www.azoquantum.com/News.aspx?newsID=9988].
More detections of FRBs should reveal whether this changing pattern is common or unique to 121102. Astronomers also plan to analyze new bursts at higher radio frequencies [https://www.channel3000.com/news/national-and-world-news/astronomers-detect-signals-from-a-galaxy-almost-a-billion-light-years-away-2022/video_eda408f9-33b9-54ee-8ba5-ccb8fb773016.html]. This can fingerprint the environment near an FRB’s source.
“If we find more FRBs nestled inside turbulent galaxies with properties like this one, it will strengthen the case that neutron stars are behind these mysterious signals,” concluded Dr. Pleunis.
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