Total Amount of Light in the Universe
Scientists have always wondered how much light exists in the universe. However, measuring it from Earth is difficult because the Sun and space dust interfere with observations.
To get a clearer answer, NASA sent the New Horizons space probe far from the Sun. After 18 years of travel, the probe is now 7.3 billion kilometers away in a distant region called the Kuiper Belt. This area is very cold and far from the inner Solar System, making it the perfect place to measure the total amount of light in space.
What Did New Horizons Discover?
New Horizons has provided the most accurate measurement of all the visible light in the universe. Scientists found that almost all the light comes from galaxies—groups of stars, gas, and dust held together by gravity. This matches what space researchers expected based on how galaxies have emitted light over the past 12.6 billion years.
Astronomer Marc Postman from NASA’s Space Telescope Science Institute said, “We now know how dark space really is. Almost all the light comes from galaxies, and we haven’t found any unknown sources of light.”
What’s Next for New Horizons?
New Horizons was launched on January 19, 2006, to study Pluto and its five moons. It completed that mission in 2015, but NASA has decided to extend its operation. The probe will continue traveling until it leaves the Kuiper Belt around 2028 or 2029.
This mission helps astronomers better understand the brightness of the universe and confirms that galaxies are the main sources of visible light.
