Scientists have recently conducted a study to measure the cosmic optical background, the faint glow that permeates the universe. Using data from NASA’s New Horizons spacecraft, which is currently over 5.5 billion miles from Earth, researchers sought to determine just how bright this glow is compared to sunlight reaching Earth’s surface. The findings suggest that the cosmic optical background is approximately 100 billion times fainter than sunlight, making it too dim for human eyes to see.
The cosmic optical background is a phenomenon that has intrigued scientists for nearly 50 years. It provides insights into the history of the universe since the Big Bang and helps confirm our understanding of how the cosmos has evolved over time. Scientists believe that the first galaxies formed during the Cosmic Dawn, hundreds of millions of years after the Big Bang, and that starlight from distant galaxies reached its peak brightness around 10 billion years ago. Precise measurements of the cosmic optical background can either verify this model of the cosmos or reveal unknown objects emitting light into space.
Measuring the cosmic optical background accurately is a challenging task, as Earth’s atmosphere contains dust and debris that can interfere with the signals coming from space. To overcome this, researchers utilized the New Horizons spacecraft, which provided a unique opportunity to capture these measurements from the edge of the solar system. By pointing the spacecraft’s Long Range Reconnaissance Imager (LORRI) at different patches of the sky, the team was able to estimate the amount of light generated by the Milky Way Galaxy’s halo and subtract it from the cosmic optical background.
The study’s results indicate that the cosmic optical background amounts to approximately 11 nanowatts per square meter per steradian, a value that aligns well with the number of galaxies scientists believe have formed since the Big Bang. While the measurements suggest that there are no unusual objects generating excessive light in space, researchers cannot rule out the possibility of undiscovered anomalies. Due to the limitations of the New Horizons spacecraft and the lack of future missions heading towards these regions of space, these measurements are likely to remain the best estimates of the universe’s glow for the foreseeable future.
The cosmic optical background study was led by Marc Postman at the Space Telescope Science Institute and included researchers from various institutions such as the University of Colorado Boulder and Southwest Research Institute. The mission had its origins in Colorado, with Alan Stern, who leads the New Horizons mission, having studied at CU Boulder under Michael Shull. The collaborative effort involved pointing LORRI at different patches of sky to capture accurate measurements of the cosmic optical background. While future missions with more advanced instruments may provide more precise measurements in the future, the current study represents a significant step forward in our understanding of the faint glow that permeates the universe.