Blobs of Dark Matter

Dark matter fluctuations in the lens system MG J0414+0534. The whitish blue color represents the gravitationally lensed images observed by ALMA. The calculated distribution of dark matter is shown in orange; brighter regions indicate higher concentrations of dark matter and dark orange regions indicate lower concentrations.  Credit: ALMA (ESO/NAOJ/NRAO), K. T. Inoue et al.

Astronomers Observe Blobs of Dark Matter Down to a Scale of 30,000 Light-Years Across

Dark matter remains mysterious and… well… dark. While we don’t yet have a definite idea of what this cosmic “stuff” is made of, astronomers are learning more about its distribution throughout the Universe. 

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Since we can’t see it directly, observers need to use indirect methods to detect it. One way is through gravitational lensing. Another is by looking for emissions from hydrogen gas associated with small-scale dark matter structures in the Universe.

A group of astronomers led by Kaiki Taro Inoue of Kindai University in Japan used the Atacama Large Millimeter Array in Chile to study a distant gravitational lens system called MG J0414+534. A massive foreground galaxy is bending and distorting the light from a distant quasar that lies some 11 billion light-years away. 

The result is four images of the quasar. When they looked at the data, the team found some strange anomalies in the images. They are actually variations in the distribution of dark matter along the line of sight between us and the quasar. 

The gravitational lens magnified the fluctuations and analysis of the data allowed them to map the fluctuations down to a scale of 30,000 light-years.

What The Blobs of Dark Matter Mean
Throughout the universe, dark matter is associated with massive galaxies and galaxy clusters. However, small-scale clumps and distributions aren’t as well understood. So, astronomers want to find ways to map the smaller concentrations of it. Gravitational lensing provides one way to do that. 

In the case of MG J0414+0534, the positions and shapes of the lensed quasar images look a little strange. They don’t fit the model of gravitational lensing predicted when you plug in the numbers for the galaxy and its associated dark matter component.  READ MORE...

Dark Energy

This diagram reveals changes in the rate of expansion since the universe’s birth nearly 15 billion years ago. The more shallow the curve, the faster the rate of expansion. The curve changes noticeably about 7.5 billion years ago when objects in the universe began flying apart at a faster rate. Astronomers theorize that the faster expansion rate is due to a force called “dark energy” that is pulling galaxies apart. Credit: NASA/STSci/Ann Feild






Dark Energy Was Always Present, Everywhere and at Every Time


The Force is with us, according to cosmologists working to understand a mysterious “something” that’s making the universe expand. Its name? Dark energy. And, it turns out that it’s been present everywhere throughout cosmic history.

Astronomers have known since the 1920s that the universe is expanding. That understanding began with Edwin Hubble’s groundbreaking observation of a Type I supernova in the Andromeda Galaxy. 

And, astronomy trucked along for many years, using that expansion to measure distances and other parameters in the cosmos. Then, in 1998, something happened. Astronomers discovered that the cosmic expansion is speeding up.

The culprit? This completely not-at-all-understood dark energy force which can’t be seen, but with effects that can be detected. Some explain it as a property of space that causes the universe to expand faster and faster. 

Others suggest that it’s some kind of new energy fluid or a field that fits throughout space, but has an effect on the expansion of the Universe. It could also be something that doesn’t fit our current theories about gravity, and that a new theory of gravity could account for dark energy’s effects.

There’s no consensus yet about which of these theories is correct. However, its discovery immediately raised a bunch of questions, such as, when did the expansion rate accelerate? Will that change, too? Was it the same rate throughout the universe across all time?

Dark Energy, eROSITA, and Galaxy Clusters

To answer those, a group of researchers used something called eROSITA to look at a specific subset of galaxy clusters across time. eROSITA is the main X-ray-sensitive instrument aboard the Spectrum-ROENTGEN-GAMMA (SRG) mission launched in 2019. (Currently, it is shut down due to the ongoing conflict between Russia and Ukraine.) 

One of its jobs is to do a complete all-sky survey in the medium energy X-ray range (up to 10 keV). The data it returns should help probe the nature and ubiquity of dark energy by studying up to 100,000 galaxy clusters and the material between them. It also studies obscured black holes in galaxies and looks at X-ray sources ranging from young stars and supernova remnants to X-ray binaries.

Astronomers I-Non Chieu of Taiwan’s National Cheng Kung University and Matthias Klein, Sebastian Bocquet, and Joseph Mohr at Ludwig Maximilians-Universitat in Munich used eROSITA Final Equatorial Depth Survey (eFEDS) data taken before the shutdown to characterize about 500 low-mass galaxy clusters. 

It’s one of the largest such samples and it “saw” them over the past ten billion years. That’s around 3/4 of the age of the Universe.  READ MORE...

Our Universe - Gravity Creates Light

A star is being consumed by a distant supermassive black hole. Astronomers call this a tidal disruption event (TDE). As the black hole rips apart the star, two jets of material moving with almost the speed of light are launched in opposite directions. One of the jets was aimed directly at Earth. Image credit: Carl Knox (OzGrav, ARC Centre of Excellence for Gravitational Wave Discovery, Swinburne University of Technology)

Physicists Discover that Gravity Can Create Light
Researchers have discovered that in the exotic conditions of the early universe, waves of gravity may have shaken space-time so hard that they spontaneously created radiation.

The physical concept of resonance surrounds us in everyday life. When you’re sitting on a swing and want to go higher, you naturally start pumping your legs back and forth. You very quickly find the exact right rhythm to make the swing go higher. If you go off rhythm then the swing stops going higher. This particular kind of phenomenon is known in physics as a parametric resonance.

Your legs act as an external pumping mechanism. When they match the resonant frequency of the system, in this case your body sitting on a swing, they are able to transfer energy to the system making the swing go higher.

These kinds of resonances happen all over the place, and a team of researchers have discovered that an exotic form of parametric resonance may have even occurred in the extremely early universe.

Perhaps the most dramatic event to occur in the entire history of the universe was inflation. This is a hypothetical event that took place when our universe was less than a second old. During inflation our cosmos swelled to dramatic proportions, becoming many orders of magnitude larger than it was before. The end of inflation was a very messy business, as gravitational waves sloshed back and forth throughout the cosmos.  READ MORE...