How many galaxies are there outside ours?
NASA’s July 2015 New Horizons probe was a historical moment when it did a close flyby of Pluto.
Later, New Horizons had an encounter with a Kuiper Belt Object (KBO) – known as Arrokoth (AKA 2014 MU69) on December 2018. Astronomers started conducting experiments on it after seeing it’s strange position in the outer Solar System. Among this were parallax measurements of Proxima Centauri and Wolf 359, the two stars closest to the Solar System.
The Cosmic Optical Background
Aside from looking into Arrokoth, a team of astronomers led by the National Optical Astronomy Observatory (NOAO) and Southwest Research Institute (SwRI) measured the Cosmic Optical Background (COB) using the data obtained from the Long Range Reconnaissance Imager (LORRI) probe.
COB is the light from every source located outside the Milky Way that is scattered over every part of the Universe that we can see. It is also the visible light analogue of the Cosmic Microwave Background (CMB) and is an important standard set by the astronomers. They identify the locations of stars, the size and density of galaxies, and test theories about the structure and formation of the cosmos using this light.
Being able to measure the COB accurately has many reasons of significance. It is an important part of the history of star formation, star clusters, galaxies, black holes, galaxy clusters, and pretty much every massive structure included in the universe. Hence, being able to determine just how dark the night sky is can help us know about how the universe was formed and evolved afterwards.
A diffuse component of the COB called dCOB, which is a collection of photons is being looked into by scientists. This would help them know how much of the cosmic background light can be coming for sources in the low density regions of the Universe.