It is very difficult to analyse how dark the universe really is especially when you are next to the sun. A recent study by Nasa’s New Horizon took the pictures far away from the universe to give the most accurate results of the spread background light in the universe. The other name given to this diffusion of background light is Cosmic Optical Background.
In general, it is the combination of all the universe lights such as light by all the stars and galaxies in space. Similar to this is the Cosmic Microwave Background the well-known cousin of the Cosmic Optical Background which tells you about the number of contents in the universe. Measuring each and every single galaxy is not possible every time regardless of how far or dim they are with our telescope so instead of that what they used to do is measure the light by all of the galaxies and from that they will get the better idea about how dark the universe really is.
A recent study by Marc Postman of the Space Telescope Science Institute in Baltimore, Maryland answered a question stating that is it really important to count the number of galaxies present in the universe.
Also just calculating the background light is not easy as we think of by just taking the images of the space and then just hoping for the best. And from observing from earth it’s a quite difficult job as there were sources of light pollution on earth. Using the Hubble telescope is also not possible at it is very close to the sun and there are many small ice particles in the solar system that reflects the sunlight also known as zodiacal light which will really confused this kind of observation.
Recently Nasa’s New Horizons spacecraft which got speed up by the object called Arrokoth of the Kuiper belt which is very far away that the zodiacal light is not the concern. The data of archived images from this research by the New Horizons spacecraft is then observed by the team of researchers to calculate the background light in the universe and came up with the result that the background light is twice as bright than expected.
To get this result team had removed a few sources of background light like milky way reflecting off the interstellar medium, galaxies that are too dim and far away to be observed etc. Even after removing light from these sources there was still light leftovers in space.
To find the exact number astronomers are still in a doubt about the excess background light and the reasons could be dwarf galaxies near the milky way that has yet to be observed, maybe there are more stars in the outer parts of the galaxies, or even the galaxies are more than it was expected earlier in the universe. And the one who can answer to all these doubts is the James Webb Space Telescope.