Fast Radio Bursts Might Originate From Nearby Stars, Not Distant Galaxies
Until recently, the origin of "fast radio bursts" was a huge mystery. The first burst was detected about six years ago, when many people thought it was a fluke given its strange nature. Astronomers at the time thought that they originated from beyond the Milky Way. However, researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) claimed in a new study that these extremely quick and bright radio pulses, the fast radio bursts, possibly originate from flaring stars within our own galaxy. These bursts, lasting typically for one thousandth of a second, do not come from galaxies located billions of light-years away, according to lead author of the study, Avi Loeb.
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Follow up studies on fast radio bursts — only six of them have been discovered so far, each only once — have been difficult because they are extremely bright and short lived packaging a huge quantum of energy in its life span.
The source of these bursts was identified on the basis of a detailed analysis which showed that the pulses on their way to Earth had to pass through a large column of electrons. "If those electrons were spread out across intergalactic space, then the pulses must have crossed billions of light-years. As a result, they would have to come from extremely energetic events," according to a Harvard-Smithsonian Center for Astrophysics press release.
Astronomers zeroed-in-on "stellar flares," not gamma-ray bursts as a source because gamma-ray bursts do not produce the correct radio frequencies. Loeb and his colleagues then considered the possibility of the source at a closer point of origin within our galaxy that would require less energy. The reason stellar flares fit the bill is that "tightly packed electrons in the stellar corona would cause the same effect as he more diffuse intergalactic electrons", according to the press release.
Radio bursts are caused by two types of stars: young low-mass stars, and solar-mass "contact" binaries — two stars that share their outer gaseous envelopes as they orbit close to eachother. Both of them also fluctuate in brightness at visible light or optical wavelengths. Loeb and his colleagues used the telescopes at Tel-Aviv University's Wise Observatory in Israel as they searched the locations of three fast radio bursts to look for variable stars.
While monitoring those fields for several nights looking for unusual occurrences, they could identify a location to be home to a contact binary consisting of two sun like stars, about 2,600 light-years from Earth, orbiting each other every 7.8 hours. A new class of sources invariably leads to the debate whether they are close or distant, according to Loeb. Gamma-ray bursts led initially to a similar debate. Its source was speculated to be in the Milky Way. Later, however, astronomers determined its source to actually be far away in cosmological distances. The case of fast radio bursts was just the opposite. Its source, initially thought distant, is actually near home in our own Milky Way, according to Loeb.
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