Experts Have Made A New and Improved Dark Matter Map of the Universe

Bringing us one step closer to understanding the mysterious matter that takes up about a quarter of the Universe

Hiya!

There are several grand mysteries we hope to understand someday. How does consciousness form? Or, for that matter, what is it? Why are we here? What/Who created the universe? Are we alone? What’s inside a black hole? What’s the deal with dark matter and energy? The answers to these questions and more will likely remain elusive for a while longer, but experts are slowly chipping away at them with each new discovery.

For instance, on April 11, 2023, astronomers unveiled an updated map of dark matter— one that surpasses previous models in both detail and accuracy—at the Future Science with CMB x LSS conference at Japan’s Yukawa Institute for Theoretical Physics. If that’s not impressive enough, the map also confirms Albert Einstein’s predictions about dark matter based on his theory of general relativity.

Building Blocks

Heads up: This section is a smidge dense, but I ask that you bear with me. I promise this will help us better understand the new research afterward.

I’m sure you have at least a broad understanding of Einstein’s 1915 theory of general relativity. Generally (ha!) speaking, the theory helps explain several subjects, including gravity, the existence of black holes, and planets’ motions.

Einstein argued that an object’s mass “warps” the fabric of spacetime, thus creating what we experience as gravity. His theory also provides a way to calculate specific predictions about the formation and evolution of large-scale structures such as planets, stars, and galaxies. The theory of general relativity played a significant role in teaching us about the universe’s journey over the last 13.8 billion years since the Big Bang.

Together, these predictions pretty much compose the standard model of cosmology, also known as the ACDM Model or the Concordance Cosmological Model. Basically, it assumes the Big Bang’s pure energy created the universe and everything in it — which is thought to be made of roughly 5 percent of ordinary matter you and I can see, 27 percent of theoretical dark matter which we can’t see, and 68 percent dark energy which is a theoretical invisible energetic force.

Technology advancement over the few decades following Einstein allowed astronomers to use radio telescopes to detect signals in the microwave region of the radio spectrum that are invisible to our eyes. In the 1960s, experts noticed permeating electromagnetic radiation in every direction throughout the universe. Experts believe it formed around 380,000 years after the Big Bang and thought it could explain how the first galaxies and their stars formed. This radiation became known as the Cosmic Microwave Background (CMB).

CMB is essentially what’s leftover from the very first freely traveling light in the universe, thanks to the constant expansion of the universe, which allows this relic radiation to fill the universe in a nearly uniform manner. Astronomers can use the CMB to estimate how fast the universe is expanding. It can also be used to measure the distribution of dark matter in large scales. The problem is scientists also observed that the rotational curves of galaxies were significantly faster than predictions.

This meant either Einstien’s theory was wrong or the universe possesses a significant and invisible mass called dark matter. If it exists, it’s thought dark matter is invisible to us because it doesn’t interact with light the way matter we’re familiar with does. Dark matter can’t be measured using our current tools. For instance, it can’t be seen in electromagnetic radiation or wavelengths.

But dark matter does have mass, and therefore it interacts with gravity. So while we can’t see it directly, experts can evaluate how dark matter interacts with “normal” matter and radiation. It also means that dark matter creates a gravitational lensing effect which we can see in the form of CMB distortions, especially when there are large concentrations.

Since the early 1990s, scientists have attempted to create a full-sky map of the cosmos. Each one becomes increasingly more accurate and detailed than the ones before it. The previous one (seen below) added data collected between 2009 to 2013 by the European Space Agency’s Planck satellite, which measured and mapped subtle temperature fluctuations CMB.

The full-sky image of the temperature fluctuations (shown as color differences) in the CMB over nine years. These are the seeds of galaxies from when the universe was under 400,000 years old. Image Credit: NASA

Phew. You did it!! Now for the fun part!