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A common belief among astronomers is that galaxy groups and clusters differ mainly in the number of galaxies they contain—there are fewer galaxies in groups and more in clusters. Led by Maret Einasto, astronomers at Tartu Observatory of the University of Tartu decided to look into that and discovered even more differences between groups and clusters.

The structure of the universe can be described as a giant network, a cosmic web, with chains (filaments) of single galaxies and small groups of galaxies connecting rich galaxy groups and clusters that can contain thousands of galaxies. Between galaxy systems, there are giant voids with almost no visible matter (galaxies and gas). Galaxy groups and clusters can, in turn, form even larger systems called superclusters.

In their study, Tartu astronomers used data on galaxy groups, their brightest galaxies (so-called main galaxies), and their surroundings. The aim was to combine these data to see whether it could provide new information about the possible classification of groups of different sizes.

We now have a standard model of cosmology, the current version of the Big Bang theory. Although it has proved very successful, its consequences are staggering. We know only 5% of the content of the universe, which is normal matter. The remaining 95% is made up of two exotic entities that have never been produced in the laboratory and whose physical nature is still unknown.

These are dark matter, which accounts for 25% of the content of the cosmos, and dark energy, which contributes 70%. In the standard model of cosmology, dark energy is the energy of empty space, and its density remains constant throughout the evolution of the universe.

According to this theory, sound waves propagated in the very early universe. In those early stages, the universe had an enormous temperature and density. The pressure in this initial gas tried to push the particles that formed it apart, while gravity tried to pull them together, and the competition between the two forces created sound waves that propagated from the beginning of the universe until about 400,000 years after the Big Bang.

What can the night sky tell us about the expansion of the universe?

It’s a loaded question, one that researchers across the globe have been trying to answer for decades. Since 2013, they’ve been helped by the Dark Energy Survey (DES), a collaboration of more than 400 scientists at 25 institutions. At Penn, this includes Masao Sako, Arifa Hasan Ahmad and Nada Al Shoaibi Presidential Professor of Physics and Astronomy; Bhuvnesh Jain, Walter H. and Leonore C. Annenberg Professor in the Natural Sciences; Gary Bernstein, Reese W. Flower Professor of Astronomy and Astrophysics; and a handful of others from the Department of Physics & Astronomy.

In 2019, the DES finished collecting data, but analysis and discoveries continue, including one that Sako and colleagues announced recently in which they validated the “cosmic acceleration” model and dark energy’s role in it. That research is one of five recent studies detailed below, in this second iteration of Omnia’s new research roundup.

Astronomers have spotted an unusual sign that a dead star feasted on a fragment of a planet orbiting it: a metal scar on the star’s surface. The revelation sheds light on the dynamic nature of planetary systems even in the end stages of a star’s life cycle — and could foretell the eventual fate of our own solar system, according to the scientists.

Planets form from swirls of gas and dust called a protoplanetary disk that surrounds a newly formed star. But as the star ages and dies, the stellar object can consume the very planets and asteroids it helped create.

Astronomers observed a dead star, known as a white dwarf, located about 63 light-years away from Earth using the European Southern Observatory’s Very Large Telescope in Chile. The observation revealed a metallic feature on the star’s surface that the researchers determined was related to a change detected in the star’s magnetic field. A new study detailing the observation appeared Monday in The Astrophysical Journal Letters.

As Space.com reports, the uber-powerful James Webb Space Telescope and its predecessor, the Hubble, have observed a super-long gamma-ray burst (GRB) that occurred when two dense neutron stars collided millions of years ago — and the result, as the telescopes’ instruments detected, was quite literally pure gold.

Neutron stars are the rare result of supernovas, or the explosions associated with dying stars, that don’t turn into black holes. Earlier this week, in fact, the JWST was used to detect the neutron star at the heart of a well-known supernova that scientists believed existed but couldn’t see until now.

Because these bodies are, essentially, small and dense balls of mass, it’s not surprising that something huge happens when they collide. With the power of these two magnificent telescopes, scientists from the University of Rome were able to spot the bright shine, known as a kilonova, of the heavy elements like silver and gold created in the dead stars’ turbulent merger.

What is the shape of our universe? A question that has captivated us for a very long time. A recently published paper arrived at a conclusion that may shake up the field of cosmology tremendously.

We could be closer to understanding the mystery behind what dark matter is, following new research from physicists at King’s College London.

First theorized in 1977, axions are a hypothetical, light-mass particle that have been suggested as a possible contender for dark matter, due to the heat they give off. However, due to the range of sizes and masses they could possibly be, their conclusive identification has been difficult.

In a series of papers in Physical Review D, Liina Chung-Jukko, Professors Malcolm Fairbairn, Eugene Lim, Dr. David Marsh and collaborators have suggested a new approach to locate this ‘wonder particle’ that could explain both dark energy and dark matter.

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