It is a powerful observatory that has provided enormous amounts of data on gamma rays (the most energetic form of light) and their interaction with the extragalactic background light
(EBL), which is a cosmic fog composed of all the ultraviolet, visible and infrared light emitted by stars or from dust in their vicinity.
"Though some challenges remain, further data from LORRI could provide a definitive measurement of the extragalactic background light
at optical wavelengths, and may be instrumental in completing our understanding of the history of stars and galaxies in the universe," the researchers wrote in the study.
They were trying to decipher the extragalactic background light
, or EBL, a diffuse glow that fills the universe (SN:9/7/13, p.
That bath of ancient and young photons suffusing the Universe today is called the extragalactic background light
The combination of its superior location and experimental capabilities led to a long list of exciting discoveries of several very high energy (VHE) gamma ray sources over the past few years, including supernova remnants, the source at the Galactic Centre, compact binary systems, microquasars, pulsar wind nebulae, gamma rays from cosmic-ray interactions with dense molecular clouds, a starburst galaxy, stellar and galaxy clusters, active galactic nuclei, and "dark sources" with no obvious counterparts, in addition to conducting the first VHE survey of the sky, measuring the local cosmic-ray electron and iron nuclei spectra, constraining the level of extragalactic background light
, and providing upper limits to dark mater annihilation.
But measuring the extragalactic background light is a challenge researchers are eager to take on.
In 1992, astrophysicist Floyd Stecker of NASA Goddard and his colleagues suggested using this drop-off between the expected and observed gamma rays to measure how much extragalactic background light exists between the blazar and Earth.
Over such a great distance, a substantial proportion of the gamma rays should be absorbed by the extragalactic background light
, but calculations that account for the expected absorption yield an unexpected emission spectrum for the blazar.
The light emitted by all the objects in the Universe (stars, galaxies, etc) ever since its birth fills intergalactic space with an 'ocean' of photons known as the 'diffuse extragalactic background light
The total sum of starlight in the cosmos is known to astronomers as the extragalactic background light