Astronomers have finally found the last of the missing universe. It’s been hiding since the mid-1990s, when researchers decided to inventory all the “ordinary” matter in the cosmos—stars and planets and gas, anything made out of atomic parts. (This isn’t “dark matter,” which remains a wholly separate enigma.) They had a pretty good idea of how much should be out there, based on theoretical studies of how matter was created during the Big Bang. Studies of the cosmic microwave background (CMB)—the leftover light from the Big Bang—would confirm these initial estimates.

So they added up all the matter they could see—stars and gas clouds and the like, all the so-called baryons. They were able to account for only about 10 percent of what there should be. And when they considered that ordinary matter makes up only 15 percent of all matter in the universe—dark matter makes up the rest—they had only inventoried a mere 1.5 percent of all matter in the universe.

Now, in a series of three recent papers, astronomers have identified the final chunks of all the ordinary matter in the universe. (They are still deeply perplexed as to what makes up dark matter.) And despite the fact that it took so long to identify it all, researchers spotted it right where they had expected it to be all along: in extensive tendrils of hot gas that span the otherwise empty chasms between galaxies, more properly known as the warm-hot intergalactic medium, or WHIM.

Everything we think we know about the shape of the universe could be wrong. Instead of being flat like a bedsheet, our universe may be curved, like a massive, inflated balloon, according to a new study.

That’s the upshot of a new paper published today (Nov. 4) in the journal Nature Astronomy, which looks at data from the cosmic microwave background (CMB), the faint echo of the Big Bang. But not everyone is convinced; the new findings, based on data released in 2018, contradict both years of conventional wisdom and another recent study based on that same CMB data set.

Related: From Big Bang to Present: Snapshots of Our Universe Through Time.

There are a lot of unsolved mysteries in the Universe, but dark energy is the most confusing. Here’s why.

A trio of researchers with the University of Manchester, Università di Roma ‘La Sapienza’ and Sorbonne Universities has sparked a major debate among cosmologists by claiming that data from the Planck space observatory suggests the universe is a sphere—not flat, as current conventional theory suggests. In their paper published in the journal Nature Astronomy, Eleonora Di Valentino, Alessandro Melchiorri and Joseph Silk outline their arguments and suggest their findings indicate that there exists a cosmological crisis that must be addressed.

Conventional theory, which backs inflation theory, suggests that after the Big Bang, the universe expanded in a way that was flat—two lights shone in parallel would travel forever in parallel. But now, after studying data sent back to Earth from the Planck space observatory (which mapped cosmic microwave background radiation over the years 2009 to 2013) Di Valentino, Melchiorri and Silk have come to disagree with conventional thinking. They claim that there is evidence that the universe is closed—that it is shaped like a sphere. If you shine two lights into the dark of space, they suggest, at some point, the light would come back around to you from behind.

The researchers came to this conclusion after looking at data from the Planck space observatory that showed a discrepancy between the concentration of dark matter and dark energy and outward expansion; there was more gravitational lensing than theory has predicted. Such an imbalance, they claim, would have the universe collapsing in on itself, resulting in a sphere shape. Others who have looked at the same data prior to this new effort have called the data from the observatory a statistical fluke. The research trio note that there are other problems with the flat theory as well, such as scientists’ inability to accurately measure the Hubble constant; each team that tries finds a different answer. There have also been problems with reconciling surveys of dark energy with a flat model.

According to the theory of General Relativity, mass curves spacetime. As a result, the overall mass of the universe determines its shape. Indeed, scientists have been known to calculate the “critical density” of the universe, which is proportional to the square of the Hubble constant, a variable used in estimating the size, age and expansion rate of the universe. If the actual density of the universe is less than the critical density, it is predicted that the universe will forever expand, as there isn’t enough matter to stop it. This creates a flat, and open, universe.

Yet if the density of the universe is more than the critical density, then that means it has enough mass to stop expanding, which is what the latest study using Planck data is suggesting.

A closed universe could end consequentially with a scenario known as the “Big Crunch” — the opposite of a Big Bang, in a sense, and a state in which the universe contracts until it is compressed again to a single energetic point.

For years scientists have believed our universe was as flat as a piece of paper, but new evidence has suggested it is curved like a giant inflated balloon.

A recent study analyzed data from the cosmic microwave background, the faint echo of the Big Bang, and discovered gravity seems to bend the microwaves.

The origin of the universe started with the Big Bang, but how the supernova explosion ignited has long been a mystery – until now. In a new paper appearing today in Science Magazine, researchers detailed the mechanisms that could cause the explosion, which is key for the models that scientists use to understand the origin of the universe.