Scientists have used some recent data from NASA's New Horizons spacecraft mission outside Pluto to measure how dark the cosmic background is. What they found has implications for what we thought we knew about the composition of the entire universe. The universe is not as densely populated as we thought.
In short, the universe is so dark, there can not be so many galaxies out there - we should be "seeing" more light. In the past the astronomers had estimated that there are 2 trillion galaxies in the universe.
"It's an important number we all need to know - how many galaxies are there after all?" Marc Postman of the Space Telescope Science Institute wondered in a statement yesterday. "We just do not see the light from 2 trillion galaxies."
That was his previous assessment arise Hubble Space Telescope observations, but a new study published in the Astrophysical Journal suggests that the total number galaxies in the universe are probably in the hundreds of billions instead of the trillions.
The fact that NASA's New Horizons is close to the edge of the solar system makes it see a darker image of the universe - it is actually 10 times darker - from where the Hubble Telescope sits.
"These kinds of measurements are extremely difficult. Many have tried to do the right thing at different times measurementsSaid co-author of the study Tod Lauer. "New Horizons because of its location has given us the advantage of measuring the cosmic visual background better than in the past."
The team's results will be presented at a meeting on Wednesday American Astronomical Society.
The upcoming space telescope James Webb, which is due to start on 31 October, could help provide further information on the number and the type of galaxies that provide the faint glow to background which prevents the universe from being completely black.
Source of information: cnet.com