Evidence of Dark Matter Interacting With Itself in El Gordo Merger

This image is from a computer simulation of the distribution of matter in the universe. Orange regions host galaxies; blue structures are gas and dark matter. We can map dark matter, but we don't know what it is. Image Credit: TNG Collaboration

The Standard Model of particle physics does a good job of explaining the interactions between matter’s basic building blocks. But it’s not perfect. It struggles to explain dark matter. Dark matter makes up most of the matter in the Universe, yet we don’t know what it is.

The Standard Model says that whatever dark matter is, it can’t interact with itself. New research may have turned that on its head.

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The Milky Way’s History is Written in Streams of Stars

This artist’s impression shows a myriad of stellar streams in and around the Milky Way. These stretched-out remnants of dwarf galaxies and star clusters showcase gravitational interactions between stars, clumps of dark matter, and the entire galaxy. Rubin Observatory will reveal many more stellar streams than we have seen thus far, enabling scientists to study our galaxy’s history and properties of dark matter in more detail than ever before. Image Credit: NOIRLab

The Milky Way is ancient and massive, a collection of hundreds of billions of stars, some dating back to the Universe’s early days. During its long life, it’s grown to these epic proportions through mergers with other, smaller galaxies. These mergers punctuate our galaxy’s history, and its story is written in the streams of stars left behind as evidence after a merger.

And it’s still happening today.

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The Milky Way’s Smallest, Faintest Satellite Galaxy Found

Hidden in this deep sky image (left) is Uma3/U1, an ultra faint galaxy. It contains fewer than 100 hundred stars, a tiny amount for a galaxy. Credit: CFHT/S. Gwyn (right) / S. Smith (left)

The Milky Way has many satellite galaxies, most notably the Large and Small Magellanic Clouds. They’re both visible to the naked eye from the southern hemisphere. Now astronomers have discovered another satellite that’s the smallest and dimmest one ever detected. It may also be one of the most dark matter-dominated galaxies ever found.

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There Aren’t Many Galaxies Like The Milky Way Nearby. Now We Know Why

Antennas of the Very Large Array against the Milky Way. Credit: NRAO/AUI/NSF/Jeff Hellerman

The Milky Way is a barred spiral galaxy, maybe even a grand design spiral galaxy. We can’t be sure from our vantage point. But one thing is certain: there aren’t many disk galaxies like it in our part of the Universe called the supergalactic plane.

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Dark Matter Might Interact in a Totally Unexpected Way With the Universe

Image from Dark Universe, showing the distribution of dark matter in the universe. Credit: AMNH

According to Sir Isaac Newton’s theory of Universal Gravitation, gravity is an action at a distance, where one object feels the influence of another regardless of distance. This became a central feature of Classical Newtonian Physics that remained the accepted canon for over two hundred years. By the 20th century, Einstein began reconceptualizing gravity with his theory of General Relativity, where gravity alters the curvature of local spacetime. From this, we get the principle of locality, which states that an object is directly influenced by its surroundings, and distant objects cannot communicate instantaneously.

However, the birth of quantum mechanics has caused yet another conceptualization, as physicists discovered that non-local phenomena not only exist but are fundamental to reality as we know it. This includes quantum entanglement, where the properties of one particle can be transferred to another instantaneously and regardless of distance. In a new study by the International School for Advanced Studies (SISSA) in Trieste, Italy, a team of researchers suggests that Dark Matter might interact with gravity in a non-local way.

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“Early Dark Energy” Could Explain the Crisis in Cosmology

A diagram of the evolution of the observable universe. The Dark Ages are the object of study in this new research, and were preceded by the CMB, or Afterglow Light Pattern. By NASA/WMAP Science Team - Original version: NASA; modified by Cherkash, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11885244
A diagram of the evolution of the observable universe. Credit: NASA/WMAP/Wikimedia

In 1916, Einstein finished his Theory of General Relativity, which describes how gravitational forces alter the curvature of spacetime. Among other things, this theory predicted that the Universe is expanding, which was confirmed by the observations of Edwin Hubble in 1929. Since then, astronomers have looked farther into space (and hence, back in time) to measure how fast the Universe is expanding – aka. the Hubble Constant. These measurements have become increasingly accurate thanks to the discovery of the Cosmic Microwave Background (CMB) and observatories like the Hubble Space Telescope.

Astronomers have traditionally done this in two ways: directly measuring it locally (using variable stars and supernovae) and indirectly based on redshift measurements of the CMB and cosmological models. Unfortunately, these two methods have produced different values over the past decade. As a result, astronomers have been looking for a possible solution to this problem, known as the “Hubble Tension.” According to a new paper by a team of astrophysicists, the existence of “Early Dark Energy” may be the solution cosmologists have been looking for.

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Finally, an Explanation for the Cold Spot in the Cosmic Microwave Background

Map of the cosmic microwave background (CMB) sky produced by the Planck satellite. The Cold Spot is shown in the inset, with coordinates and the temperature difference in the scale at the bottom. Credit: ESA/Durham University.

According to our current Cosmological models, the Universe began with a Big Bang roughly 13.8 billion years ago. During the earliest periods, the Universe was permeated by an opaque cloud of hot plasma, preventing atoms from forming. About 380,000 years later, the Universe began to cool and much of the energy generated by the Big Bang converted into light. This afterglow is now visible to astronomers as the Cosmic Microwave Background (CMB), first observed during the 1960s.

One peculiar characteristic about the CMB that attracted a lot of attention was the tiny fluctuations in temperature, which could provide information about the early Universe. In particular, there is a rather large spot in the CMB that is cooler than the surrounding afterglow, known as the CMB Cold Spot. After decades of studying the CMB’s temperature fluctuations, a team of scientists recently confirmed the existence of the largest cold spots in the CMB afterglow – the Eridanus Supervoid – might be the explanation for the CMB Cold Spot that astronomers have been looking for!

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A Particle Physics Experiment Might Have Directly Observed Dark Energy

An illustration of cosmic expansion. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

About 25 years ago, astrophysicists noticed something very interesting about the Universe. The fact that it was in a state of expansion had been known since the 1920s, thanks to the observation of Edwin Hubble. But thanks to the observations astronomers were making with the space observatory that bore his name (the Hubble Space Telescope), they began to notice how the rate of cosmic expansion was getting faster!

This has led to the theory that the Universe is filled with an invisible and mysterious force, known as Dark Energy (DE). Decades after it was proposed, scientists are still trying to pin down this elusive force that makes up about 70% of the energy budget of the Universe. According to a recent study by an international team of researchers, the XENON1T experiment may have already detected this elusive force, opening new possibilities for future DE research.

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Cosmic Dawn Holds the Answers to Many of Astronomy’s Greatest Questions

A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).

Thanks to the most advanced telescopes, astronomers today can see what objects looked like 13 billion years ago, roughly 800 million years after the Big Bang. Unfortunately, they are still unable to pierce the veil of the cosmic Dark Ages, a period that lasted from 370,000 to 1 billion years after the Big Bang, where the Universe was shrowded with light-obscuring neutral hydrogen. Because of this, our telescopes cannot see when the first stars and galaxies formed – ca., 100 to 500 million years after the Big Bang.

This period is known as the Cosmic Dawn and represents the “final frontier” of cosmological surveys to astronomers. This November, NASA’s next-generation James Webb Space Telescope (JWST) will finally launch to space. Thanks to its sensitivity and advanced infrared optics, Webb will be the first observatory capable of witnessing the birth of galaxies. According to a new study from the Université de Genève, Switzerland, the ability to see the Cosmic Dawn will provide answers to today’s greatest cosmological mysteries.

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What is the Steady State Hypothesis?

Artist's impression of the Milky Way Galaxy. Credit: ESO

When it comes to our cosmic origins, a number of theories have been advanced throughout the course of history. Literally every culture that’s ever existed has had its own mythological tradition, which naturally included a creation story. With the birth of the scientific tradition, scientists began to understand the Universe in terms of physical laws that could be tested and proven.

With the dawn of the Space Age, scientists began testing cosmological theories in terms of observable phenomena. From all of this, a number of theories emerged by the latter half of the 20th century that attempted to explain how all matter and the physical laws governing it came to be. Of these, the Big Bang Theory remains the most widely accepted while the Steady-State Hypothesis has historically been its greatest challenger.

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