Scientists recently used data from NASA’s New Horizons mission beyond Pluto to measure how dark the cosmic background really is. What they found has implications for what we thought we knew about the composition of the entire universe.
In short, space is so dark that there can not be as many galaxies out there, adding their faint glow to the background that astronomers have previously estimated.
“That’s an important number to know – how many galaxies are there?” Marc Postman of the Space Telescope Science Institute said in a statement Tuesday. “We simply do not see the light from 2 trillion galaxies.”
It was the previous estimate derived from Hubble Space Telescope observations, but a new study published in the Astrophysical Journal and co-author of Postman suggests that the total number of galaxies in the universe is probably in the hundreds of billions rather than trillions. .
Interestingly, this is closer to an even earlier figure guessing that there were about 200 billion galaxies. It was based on Hubble data from the 1990s.
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New Horizons’ location near the edge of the solar system gives it an ambient sky 10 times darker than where Hubble sits.
“This kind of measurement is extremely difficult. Many people have been trying to do this for a long time,” said study author Tod Lauer of the National Optical Infrared Astronomy Research Laboratory. “New Horizons provided us with a vantage point to measure the cosmic optical background better than anyone has been able to do.”
The team’s results will be presented Wednesday at a meeting of the American Astronomical Society.
The coming, currently set for launch on Halloween, can help provide further insight into exactly how many and what type of galaxies provide the faint background glow that keeps the universe from turning completely black.
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