Scientists connected 2 of largest radio telescopes within the world require to take a close check out of the mysterious “colors” of the intergalactic phenomena referred to as fast radio bursts (FRBs).
The researchers found that, while these millisecond-long flashes of light are invisible to human eyes, they glow with a veritable rainbow of radio wavelengths — which could have big implications for what’s causing them.
“Once we analyzed the info , and compared different radio colors, we were very surprised,” Inés Pastor-Marazuela, an astrophysicist at the University of Amsterdam and lead author of a latest study on FRBs, said during a statement. The team determined the FRB was likely an isolated, slowly rotating magnetar, a very dense, highly magnetic neutron-star that crams the mass of a sun into a ball no wider than a city.
Light we cannot see
FRBs are a number of the foremost energetic outbursts within the universe, packing more energy than the sun produces in 3 days into blips of light that last just a couple of milliseconds. Thousands of FRBs flash across the universe a every-day , but our human eyes see none of them; faithful to their name, FRBs only shine in radio wavelengths, far beyond the red-edge of color spectrum .
However, the radio-frequency spectrum contains a miniature rainbow in its own-right , with shorter radio wavelengths appearing blueish to radio telescopes, and longer wavelengths appearing reddish. In their new study, the researchers took a more detailed look at radio “colors” of FRBs than ever before, by training 2 radio telescopes onto an equivalent FRB source.
Using the Low-Frequency Array (LOFAR) & Westerbork Synthesis radio telescope (two radio telescopes from different facilities within the Netherlands), the researchers staked out a periodically-repeating FRB named 20180916B, which emits a salvo of bursts every 16 days or so.
One explanation for this FRB’s predictable, repetitive schedule suggests that a binary-star is involved; every 2 week or-so , the FRB source moves ahead of its companion star (relative to Earth), briefly permitting the FRB’s light to shine across space toward our telescopes. Systems like these include constant-storm of stellar wind blowing out of the FRB source’s companion star, the researchers said — which energetic, electron-packed wind should block certain radio wavelengths.
“Strong stellar winds from the companion of the fast radio burst source were expected to let most blue, short-wavelength radio light escape the system,” Pastor-Marazuela said. “But the redder long-wavelength radio should be blocked more, or maybe completely.”
To test that hypothesis, the researchers used the 2 radio telescopes to focus on two different radio colors, watching at high, reddish frequencies with the Westerbork telescope, and low, blueish frequencies with LOFAR. If the binary model was correct, only the blue frequencies should make it past the star system’s intense winds — however, that wasn’t the case. The telescopes detected both red & blue radio frequencies emanating from the FRB, though never at same time.
“We saw 2 days of bluer radio bursts, followed by 3 days of redder radio bursts,” Pastor-Marazuela said. “We rule out original binary wind models now—something else must be happening .”
Magnetars on the move
This finding features a few big implications for FRB research. For one, the environment around this FRB is perhaps a “bare” one, the researchers said — meaning there’s likely little stellar wind hazing things up & blocking the redder light frequencies from escaping. That rules out a binary numeration system , the team said.
The better explanation is that FRB 20180916B is being made by a magnetar. because the magnetar slowly rotates, its bright magnetic flux could shine toward Earth every 2 weeks or-so , creating the repetitive FRB observed during this study.
That explanation would fit with previous FRB research, too; in 2020, scientists traced a special FRB to a known magnetar within the Milky Way , offering a definitive FRB source for 1st time. Now, by revealing FRB 20180916B’s true colors, astronomers may soon be ready to add another star thereto list.
The new study was published in the journal Nature.