Hubble Space Telescope traces 5 mysterious 'fast radio bursts' to distant spiral galaxies
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Hubble Space Telescope traces 5 mysterious ‘fast radio bursts’ to distant spiral galaxies

Hubble Space Telescope observations have added weight to a theory that explains mysterious radio energy bursts.

Five fast radio bursts (FRBs) were tracked down to the spiral arms of five distant galaxies by the long-running observatory. Because the bright flares fade so fast, FRBs are notoriously difficult to trace, and astronomers have only detected approximately 1,000 of them so far, but there are a few theories regarding their origin stories.

The study team dismissed older hypotheses connected with FRBs via deduction. Because the newly found bursts don’t come from regions full of massive stars, this set likely can’t be associated with star explosions — such as those that produce supernovas.

Using the Hubble Space Telescope, astronomers followed four rapid radio bursts to the spiral arms of four distant galaxies. FRB 190714 (top left), FRB 191001 (top right), FRB 180924 (bottom left), and FRB 190608 are the names of the bursts (bottom right). (Image credit: NASA/ESA/Alexandra Mannings (UC Santa Cruz)/Wen-fai Fong (Northwestern)/Alyssa Pagan (STScI))

These FRBs were also not caused by old city-sized star cores (or neutron stars) merging, as such collisions are rare and tend to happen far outside of galactic arms, according to the researchers. Rather, Hubble observations from 2009, 2019, and 2020 imply that FRBs are produced by magnetars, a type of strongly magnetic neutron star.

A typical magnetar has a field 10 trillion times more powerful than a refrigerator door magnet, according to Hubble officials. A 2020 analysis of the Milky Way discovered that a FRB originated in the same zone as a known magnetar, giving support to the FRB magnetar hypothesis.

The bursts were observed using ultraviolet and near-infrared light captured by Hubble’s Wide Field Camera 3, which NASA astronauts installed during the last telescope servicing mission in 2009. Combining these two wavelengths allows astronomers to estimate the mass of observed galaxies (using infrared), discover newborn stars (using ultraviolet), and search for older stars (using visible) (again, using infrared).

“The [Hubble] imaging allows us to get a better idea of the overall host-galaxy properties, such as its mass and star-formation rate, as well as probe what’s happening right at the FRB,” lead author Alexandra Mannings, a graduate student at the University of California, Santa Cruz, said in the statement.

These Hubble Space Telescope images show the locations of two fast radio bursts, FRB 190714 (top row) and FRB 180924 (bottom row) (bottom row). (Image credit: NASA/ESA/Alexandra Mannings (UC Santa Cruz)/Wen-fai Fong (Northwestern)/Alyssa Pagan (STScI))

The new work allowed astronomers to downplay another suggestion for the origin story of FRBs, too. Some past studies from ground-based telescopes suggest the bursts may come from dwarf galaxies, as the telescopes did not see spiral arms or other substantial galactic infrastructure. Scientists were able to rule out that hypothesis for this set of FRBs because to advanced image processing and analysis of Hubble data.

“We don’t know what causes FRBs, so it’s really important to use context when we have it,” study team member Wen-fai Fong, an astrophysicist at Northwestern University, said in the statement. Her team’s imaging technique has assisted in detecting other kinds of “transient” events in the sky, such as supernovas and another type of massive energy explosion known as gamma-ray bursts.

A study based on the findings will be published in the next issue of The Astrophysical Journal. A preprint version is available on Arxiv.

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