Outer space is not black: the New Horizons probe leaves scientists puzzled

Is space really black? Astronomer Todd Lauer has been wondering that for a long time. If you could see the night sky without stars, galaxies, and the rest of the known sources of visible light, would we be looking at absolute black?


The surprise is that it is not. Lauer and other researchers from NASA's New Horizons mission have used this probe's telescope and camera and have discovered something curious that they cannot explain very well: the universe is not as black as it is painted.


The space is "quite dark"

New Horizons had the original mission to study Pluto, but it already passed the dwarf planet in 2015 and fulfilled its mission , and now it has simply continued its journey and is currently about 7.4 billion kilometers from Earth.


That means this spacecraft is now far from any source of light pollution that could prevent it from detecting light signals from the universe itself.


As these astronomers explained, both around our planet and in the inner part of the solar system, space is full of dust particles that are illuminated by the Sun and that create a diffuse glow throughout the sky, but the light that comes from the sun it is much weaker where New Horizons is now.


To try to answer that initial question, astronomers used the probe's instruments to analyze the outer space around it. They selected images that they qualify as a blank sky, where there are certain small lights from distant stars and galaxies but very dim.


They processed those images to eliminate all sources of visible light. After eliminating the light that comes from the stars and the light that comes from the Milky Way they also eliminated any stray light from the camera's peculiarities. The theoretically the result was to be left only with the light that came from beyond our own galaxy.


Even then they were not satisfied: they went further and subtracted the light that could be attributed to the galaxies that could have been captured by those cameras. Even doing all that, there was still light in an image that was not totally black when it should be.


Pluto and Charon, as seen by New Horizons. Photo: JHUAPL / SwRI.


In fact, Marc Postman, one of the astronomers involved in the study, pointed out that the amount of light that came from unknown sources was equivalent to that coming from known galaxies. That left scientists puzzled, who believe that there are either unknown galaxies out there "or another source of light that we still do not know about."


Preliminary studies that were also done with the New Horizons probe pointed in that direction without being so precise. There is no definitive explanation for a surprising phenomenon for experts and that could even be associated with dark matter.


For Lauer, as for other astronomers, the discovery is disturbing, but he ended up saying that even after all these analyzes "space is quite dark."


Via | NPR

More information | arXiv

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