Fast radio bursts could be the key to a greater understanding of the cosmos. If we can use these milliseconds-long bursts of radio waves to measure distances across space, it may help us figure out the true nature of dark energy.
We measure cosmic distances using objects called 鈥渟tandard candles鈥�, which have a predictable brightness, or luminosity. By comparing how they appear from Earth to how bright we know they actually ought to be, we can determine how far away they are.
There are only a few types of standard candles, including supernovae and stars with well-known luminosities. Now, Tetsuya Hashimoto at the National Tsing Hua University in Taiwan and his colleagues have found a property of fast radio bursts (FRBs) that may allow them to be used in a similar way.
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鈥淭he standard measures that we have all have their limitations,鈥� says Amanda Weltman at the University of Cape Town in South Africa. 鈥淚f we can find a way to use FRBs then we get a new way of constraining cosmology that should be independent of all the others.鈥� We expect to find thousands of FRBs in the coming years,聽including some聽from further away than the other standard candles, which could make them particularly useful, she says.
Hashimoto and his team compared the luminosity of a sample of 27 FRBs to the duration of the bursts and found that the two were correlated 鈥� the longer a burst lasted, the brighter it was. That means that if we can measure the duration of the burst we can estimate its intrinsic brightness and calculate its distance.
The luminosities and durations did not all match up perfectly, but the researchers calculated that there is less than a four per cent probability that they would appear as related as they do just by chance.
If the relationship is confirmed and FRBs can be used as standard candles, they may help us figure out the nature of dark energy, which is making the universe expand. If we know how far an object is, we can calculate how fast it鈥檚 moving away from us, which is dependent on the expansion of the universe. Spotting more FRBs from farther away could help us find out how that has changed since earlier in the universe鈥檚 history.
It could also give us a 鈥渟ignificant hint鈥� about what creates FRBs, which are currently of unknown origins, says Hashimoto.聽This idea that the聽longer a burst of FRBs is, the brighter it will be聽supports three particular models of what causes these mysterious signals: the interaction of a powerful jet with a cloud of debris, a collision between a neutron star and a comet or asteroid, and a shock traveling through a supernova remnant.
It鈥檚 not clear which, if any, of those models is most likely, and before FRBs are used widely as standard candles astronomers will have to figure out for sure what causes them. 鈥淭he assumption that鈥檚 going into this is that there鈥檚 only one type of FRB, and that seems unlikely,鈥� says Weltman. 鈥淲e really need to know how FRBs work before we can trust this relationship.鈥�
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