The universe is much brighter than expected: Is dark matter responsible?

The universe’s unexpectedly high brightness could be caused by the decay of an elementary particle that was only theoretically described previously and is a candidate for dark matter. Now two researchers and one researcher from the United States propose this explanation for the anomaly discovered by NASA’s New Horizons probe. In several measurements, the space probe has identified values ​​for what’s called the cosmic optical background radiation (COB) that are more than twice what was previously assumed, based on data from the Hubble Space Telescope, among other things. The new hypothesis should be verifiable using tools from New Horizons.

As the group led by José Luis Bernal of Johns Hopkins University recalls, a NASA probe has already been sent to explore Pluto and determined in two measurements at the edge of the solar system that the universe appears much brighter than expected. There, observations are not falsified by so-called zodiacal light, that is, reflections and scatterings of sunlight on dust in the interior of the solar system. No cosmic optical background radiation measurements have been made in a darker location.

The stars we know are not enough

The specific value is 16.37 ± 1.47 nW m^-2 SR^-1 For COB, it has been suggested that the galaxies we know account for only half of the background light in the universe. A possible explanation that has been proposed so far is that there are many faint, compact galaxies below the Hubble perception limit. But it should be possible to find it with the James Webb Space Telescope, it was said in the presentation. With the theory now presented, there is another hypothesis that can be verified.

The group explained about Bernal In a technical article in the scientific journal Physical Review LettersThat the elementary particle called an axion, which has been described theoretically so far, can explain the values. So it must be present first and have a mass of 8 to 20 eV. In addition, it must decay into photons in a very specific ratio. They write that the hypothesis and the values ​​determined can be verified using the Alice ultraviolet spectrometer aboard New Horizons. Further measurements are already planned. The axion is a candidate for dark matter, which has not yet been experimentally confirmed.

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