Away from the sunshine air pollution of the interior photo voltaic system, New Horizons may see how darkish the universe actually is

How dark is the universe anyway? It’s pretty hard to measure when we’re sitting this close to the sun. However, NASA’s New Horizons probe is so far away that the images it captures of the distant universe can provide the most accurate measurement of the universe’s diffuse background light.

The cosmic optical background is the name scientists give to the diffuse, general light that is given off by all stars and galaxies through all of space and time in the universe together. Like its cousin, the better known cosmic microwave background, it is an important cosmological number because it informs us about the contents of the universe. We cannot hope to use our telescopes to measure every single galaxy, no matter how far away or how dark it is. So if we measure the total light of all galaxies, we can better see how dark the universe is.

“It’s an important number to know – how many galaxies are there?” said Marc Postman of the Space Telescope Science Institute in Baltimore, Maryland, a lead author on a recent study that answered that very question.

Unfortunately, measuring this backlight isn’t as easy as just taking a picture of the room and hoping for the best.

With all of the sources of light pollution on earth, we obviously cannot do a very good job from the ground up. We can’t use the Hubble either because the telescope is too close to the sun. Tiny particles of ice throughout the solar system reflect sunlight in a phenomenon called zodiacal light that really messes up this type of observation.

However, NASA’s New Horizons starship, which was recently accelerated by the Kuiper Belt object Arrokoth, is far enough away that the zodiac light is not an issue. Using shared archived images from the probe’s main camera, a team of researchers tried to measure the backlight of the cosmos and found a number about twice as bright as expected.

To get this number, the team first subtracted some well-known background light sources such as stars in the Milky Way that are reflected from the interstellar medium and galaxies that are too dark and distant to be observed. But even after subtracting this there was still some light left.

Astronomers aren’t sure what could be causing this excessive background light. It could be a number of dwarf galaxies near the Milky Way that we have not yet observed. There could be more stars than expected scattered on the far edge of the galaxies. Or, more galaxies than expected could appear in the early universe, which the James Webb Space Telescope can answer.

Like this:

To like Loading…