Scientists Solve Cosmic Mystery: “Missing” Ordinary Matter Found in Intergalactic Space
Astronomers have finally cracked a decades-long cosmic mystery the location of the universe’s “missing” ordinary matter.
While scientists have long known that ordinary matter (the kind that makes up stars, planets, and people) accounts for only about 15% of the total matter in the universe the rest being invisible and enigmatic dark matter nearly half of this ordinary matter had remained undetected. Now, thanks to a groundbreaking study published in Nature Astronomy, researchers have discovered where it’s been hiding: in a vast, diffuse web of gas stretching between galaxies.
Led by Harvard astronomer Dr. Liam Connor, the team detected the missing matter using powerful radio signals called Fast Radio Bursts (FRBs) mysterious, millisecond-long pulses of energy that travel billions of light-years across space. As these waves travel to Earth, they are dispersed by any matter they pass through. By measuring the dispersion from 69 FRBs, scientists mapped the otherwise invisible material.
“So the question we’ve been grappling with was: Where is it hiding?” said Connor. “The answer appears to be: in a diffuse, wispy cosmic web, well away from galaxies.”
The newly detected matter, consisting of plasma (a state of matter where electrons are separated from atomic nuclei), makes up about 76% of all ordinary matter and resides in the intergalactic medium the space between galaxies. Another 15% is located in galactic halos, and just 9% is inside galaxies themselves.
This discovery helps confirm earlier calculations from cosmic microwave background radiation — the afterglow of the Big Bang which indicated how much baryonic (ordinary) matter should exist.
Why was it so hard to find? Because violent cosmic events such as supernova explosions and bursts from supermassive black holes fling vast amounts of matter out of galaxies and into deep space. Over billions of years, this process has left most baryons scattered thinly across the cosmic wilderness.
The radio bursts used in this study originated up to 9.1 billion light-years from Earth, with 39 of the signals recorded by the Deep Synoptic Array, a network of 110 radio telescopes in California.
While the mystery of ordinary matter is now largely resolved, bigger questions remain especially about dark matter, which makes up the bulk of the universe’s mass but has yet to be directly detected.
“We know exactly what ordinary matter is, we just didn’t know where it was,”
