New measurements from NASA’s New Horizons probe support the first indications that the universe appears brighter than previously assumed. The value now determined for the cosmic optical background (COB) is slightly higher than the one that caused the uproar a year ago. At the same time, the margin of error is much smaller. In general, the background in the night sky is more than twice what was previously assumed, based on data collected by the Hubble Space Telescope, among other things. Astronomers still do not have an explanation, only hypotheses have already been formulated.
An inexplicable anomaly
Like the values presented at the beginning of 2021, the data now published also comes from measurements by the New Horizons Pluto probe at the edge of the solar system. When the images were taken last September, it contained more than 51 AU from the Sun, where, among other things, there was no so-called zodiac light The measurements are falsified. This is caused by reflections and scattering of sunlight by dust in the interior of the solar system. In an even darker area, no photos of the night sky have been taken yet. Tod Lauer’s team from the National Optical Infrared Astronomy Research Laboratory removed all light sources from the images and determined the remaining optical radiation.
In this way they determined the value of 16.37 ± 1.47 nW m for the cosmic optical background radiation−2 SR−1. However, the total value of scattered light for all galaxies determined by other instruments is only half of it. Compared to the first measurement using New Horizons, the difference is now not only larger, but also more reliable. However, this cannot be explained. The proposed hypotheses include assuming that there are much more dwarf galaxies in the vicinity of the Milky Way than previously thought. Halos around galaxies could be even brighter than previously assumed. It is also possible that there are more unbound stars in intergalactic space than current theories predict.
Measurements indicate that the galaxies known to us are responsible for only half of the background light in the universe, Lauer explains science news. There is clearly an anomaly that now needs to be understood and explained, adds Mark Postman of the Space Telescope Science Institute, who helped with the analysis. It is believed that there could be many faint, compact galaxies below the Hubble Perception Limit. The James Webb Space Telescope should find them. Astrophysicist Michael Zemkoff believes that it is possible that light sources, for example at New Horizons, may be overlooked during measurements. The whole analysis Available in the trade magazine Astrophysical Journal Letters Posted.
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