Universe's Missing Matter Finally Found

With how vast the universe is, it's easy to assume that there are missing objects, unaccounted bodies, and countless mysteries drifting through the cosmos.

When it comes to universe matter, though, scientists are quite certain that they've got it all accounted for except for a last missing chunk.

Until now, that is.

The Missing Universe

According to a report from Quanta Magazine, researchers conducted an inventory of all ordinary matter or baryons in the universe back in the 1990s. Theoretical models of the Big Bang and studies on the event's afterglow known as the cosmic microwave background allowed them to make an estimate of how much matter there should be out there.

Then they basically counted all the matter that they were able to see. Ultimately, they came up with just around 10 percent of what should be available.

Considering ordinary matter only makes up 15 percent of all matter in the universe, with the rest being dark matter, the scientists realized that they were only able to account for 1.5 percent of the total matter in existence.

Astronomers were able to determine that a majority of the baryons should be in the form of hot, diffuse gas, which is, unfortunately, very challenging to find.

So where is the rest?

Uncovering The Lost Matter

Through the years, scientists recovered bits and pieces of the missing matter until their inventory included 70 percent of all existing ordinary matter in 2014.

A series of three papers from 2017 to 2018 finally reveal where the missing ordinary matter have been hiding all these years. The last one-third of ordinary matter was discovered by scientists who shared their findings in a study published in the journal Nature last June.

It turns out the final reservoir of baryons are filaments of hot gas that occupies the spaces between galaxies, which is known as the warm-hot intergalactic medium or WHIM.

"This is where nature has become very perverse," Michael Shull, co-author of the study from the University of Colorado Boulder, says in a statement. "This intergalactic medium contains filaments of gas at temperatures from a few thousand degrees to a few million degrees."

By observing a quasar called 1ES 1553, which is a black hole in a galaxy that's consuming and expelling massive quantities of gas, the international team of researchers were able to detect the signature of highly ionized oxygen gas occupying the space between the quasar and the solar system. When this gas' density is extrapolated to the entire universe, it adds up to the final 30 percent of missing matter.