New measurements show that light emitted by stars outside our galaxy is two to three times brighter than light emitted by known populations of galaxies. This observation is calling into question assumptions about the number and environment of stars in the universe. The study was led by Rochester Institute of Technology researchers. It has been posted to arXiv and accepted for publication in The Astrophysical Journal.
The team analysed hundreds of images of background light. These images were taken by NASA’s New Horizons mission’s Long-Range Reconnaissance Imager (LORRI) to calculate the cosmic optical background (COB). The COB brightness does not equal the light from known galaxies. It suggests that there may be missing optical light sources in the universe.
In Astrophysical Journal Letters earlier this year another paper is published. There an independent team of scientists reported that the COB was twice as large as previously thought. Those findings were confirmed in a new study by Symons, RIT Associate Professor Michael Zemcov. They have used a much larger set of LORRI observations. Researchers from the Jet Propulsion Laboratory at Caltech, UC Irvine, UC Berkeley, and Johns Hopkins University were also involved in this.
While measuring the COB from Earth is difficult due to dust between planets, the New Horizons spacecraft is at the edge of our solar system. There the foreground is minimal. Thus it provides a much clearer view for this type of study. The scientists hope that future missions and instruments will help them investigate the discrepancy.
“This has progressed to the point where it’s an actual mystery that needs to be solved.” This was said by Zemcov, a research professor at RIT’s Center for Detectors and School of Physics and Astronomy, said. “I’m hoping that some of the experiments we’re working on here at RIT, such as CIBER-2 and SPHEREx, will help us resolve the discrepancy.”
More information: Teresa Symons et al, A Measurement of the Cosmic Optical Background and Diffuse Galactic Light Scaling from the R < 50 AU New Horizons-LORRI Data, arXiv (2022). DOI: 10.48550/arxiv.2212.07449
Tod R. Lauer et al, Anomalous Flux in the Cosmic Optical Background Detected with New Horizons Observations, The Astrophysical Journal Letters (2022). DOI: 10.3847/2041-8213/ac573d