We have a new upper limit for the amount of light.
According to measurements of the pulsating stars scattered throughout the Milky Way and the occult radio waves from other star clusters, a particle of light – called a photon – cannot be heavier than 9.52 × 10.-46 kg.
It’s a small limit, but finding that light has any mass could significantly affect the way we interpret the Universe around us, and our understanding of physics.
Photons, usually, are defined as particles with no mass. Come on different amounts of energy zip through spacetime at a constant speed, it cannot speed up or slow down in a vacuum. This constant speed indicates no crowding, and there is no evidence to the contrary.
However, we do not know for sure that photons are massless.
Non-zero mass can have a significant effect. It would challenge Einstein’s special relativity, and Maxwell’s electromagnetic theory, possibly leading to new physics, and possibly answering big questions about the Universe (though raising more in the process).
If the photon had mass, it would have to be very small to have no significant effect on how the Universe came to be, which means we don’t have the tools to measure it directly.
But we can take indirect measurements that will give us an upper limit on this hypothetical mass, and this is exactly what a group of astronomers did.
A team from Sichuan University of Science and Engineering, the Chinese Academy of Sciences, and Nanjing University analyzed data collected by the Parkes Pulsar Interval Observatory and data on fast radio bursts from several sources to determine how bright the light might be. big
A pulsar time array is an array of radio telescope antennas to monitor neutron stars that send electromagnetic radiation beams at pulsars precise to milliseconds. Radio bursts are extremely powerful bursts of light of unknown origin that are detected in large swaths of intergalactic space.
The property the researchers investigated is known as the dispersion scale, one of the main characteristics of pulsars and fast radio bursts. It refers to how much of a powerful radio beam is scattered by the free electrons between us and the light source.
If the photons have mass, their propagation through the non-vacuum space containing the plasma is affected by the mass and free electrons in the plasma. This can cause a time delay proportional to the photon mass.
The pulsar time series looks for the time delay of the pulsars relative to each other. Especially within a wider bandwidth, the effects of dispersion can be reduced, allowing researchers to quantify how much delay can be contributed by the amount of abstract images.
Meanwhile, scattering signals from fast radio bursts can also reveal a delay proportional to the photon mass.
By carefully studying this data, the team was able to find their upper limit of 9.52 × 10.-46 kg (or, for equivalent energy, 5.34 × 10-10 electron voltages c-2) Note that this does not mean that the photon has mass; it just means that we have a new boundary where mass could fall, if it existed.
“This is the first time,” the authors write, “that the interaction between the nonzero photon mass and the plasma has been observed and quantified as the photon propagates through the plasma path.”
It’s not much lower than the measure published in 2023, but it’s an improvement. This means that scientists investigating the effects of mass spectrometry have a more accurate range to work with.
The research also highlights, astronomers say, the need for accurate radio telescopes. We may not be able to measure photons anytime soon, but getting high-quality data regularly will allow us to further narrow down the measurement, as well as its possible effects on the Universe around us.
The research is published in The Astrophysical Journal.
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