Roman Space Telescope Will Be Hunting For Primordial Black Holes

This artist's illustration shows what primordial black holes might look like. In reality, the black holes would struggle to form accretion disks. (But without them it would just be an illustration of black space.) Image Credit: NASA’s Goddard Space Flight Center

When astrophysicists observe the cosmos, they see different types of black holes. They range from gargantuan supermassive black holes with billions of solar masses to difficult-to-find intermediate-mass black holes (IMBHs) all the way down to smaller stellar-mass black holes.

But there may be another class of these objects: primordial black holes (PBHs) that formed in the very early Universe. If they exist, the Nancy Grace Roman Space Telescope should be able to spot them.

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The Universe Could Be Filled With Ultralight Black Holes That Can't Die

This simulated image shows how black holes bend a starry background and capture light. Credit: NASA’s Goddard Space Flight Center

It’s that time again! Time for another model that will finally solve the mystery of dark matter. Or not, but it’s worth a shot. Until we directly detect dark matter particles, or until some model conclusively removes dark matter from our astrophysical toolkit the best we can do is continue looking for solutions. This new work takes a look at that old theoretical chestnut, primordial black holes, but it has a few interesting twists.

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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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A New Tabletop Experiment to Search for Dark Matter

Astronomers are getting a new tool to help them in the hunt for Dark Matter. This is a rendering of the BREAD design, which stands for Broadband Reflector Experiment for Axion Detection. The ‘Hershey’s Kiss’-shaped structure funnels potential dark matter signals to the copper-colored detector on the left. The detector is compact enough to fit on a tabletop. Image courtesy BREAD Collaboration

What is Dark Matter? We don’t know. At this stage of the game, scientists are busy trying to detect it and map out its presence and distribution throughout the Universe. Usually, that involves highly-engineered, sophisticated telescopes.

But a new approach involves a device so small it can sit on a kitchen table.

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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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Dwarf Galaxies Could be the Key to Explaining Dark Matter

Dark matter map in Galaxy Cluster Abell 1689. Credit: NASA, ESA, and D. Coe (NASA JPL/Caltech and STScI)

If you have a view of the southern celestial sky, on a clear night you might see two clear smudges of light set off a bit from the great arch of the Milky Way. They are the Large and Small Magellanic Clouds, and they are the most visible of the dwarf galaxies. Dwarf galaxies are small galaxies that typically cluster around larger ones. The Milky Way, for example, has nearly two dozen dwarf galaxies. Because of their small size, they can be more significantly affected by dark matter. Their formation may even have been triggered by the distribution of dark matter. So they can be an excellent way to study this mysterious unseen material.

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This New Map of 1.3 Million Quasars Is A Powerful Tool

This figure from the research shows the sky distribution of the new Quaia quasar catalogue in Galactic coordinates and is displayed using a Mollweide projection. The grey region across the center is the Milky Way, a blind spot in the Quaia catalogue. Image Credit: K. Storey-Fisher et al. 2024

Quasars are the brightest objects in the Universe. The most powerful ones are thousands of times more luminous than entire galaxies. They’re the visible part of a supermassive black hole (SMBH) at the center of a galaxy. The intense light comes from gas drawn toward the black hole, emitting light across several wavelengths as it heats up.

But quasars are more than just bright ancient objects. They have something important to show us about the dark matter.

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Colliding Neutron Stars are the Ultimate Particle Accelerators

This artist’s impression shows two tiny but very dense neutron stars at the point at which they merge and explode as a kilonova. Such a very rare event is expected to produce both gravitational waves and a short gamma-ray burst, both of which were observed on 17 August 2017 by LIGO–Virgo and Fermi/INTEGRAL respectively. Subsequent detailed observations with many ESO telescopes confirmed that this object, seen in the galaxy NGC 4993 about 130 million light-years from the Earth, is indeed a kilonova. Such objects are the main source of very heavy chemical elements, such as gold and platinum, in the Universe.

Gamma-ray telescopes observing neutron star collisions might be the key to identifying the composition of dark matter. One leading theory explaining dark matter it that is mostly made from hypothetical particles called axions. If an axion is created within the intensely energetic environment of two neutron stars merging, it should then decay into gamma-ray photons which we could see using space telescopes like Fermi-LAT.

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Webb Can Directly Test One Theory for Dark Matter

Stephan's Quintet of galaxies as seen by JWST. The telescope could provide sharp views of even more distant galaxies that could help solve part of the dark matter mystery in galaxy formation. Courtesy: JWST.

What is it about galaxies and dark matter? Most, if not all galaxies are surrounded by halos of this mysterious, unknown, but ubiquitous material. And, it also played a role in galaxy formation. The nature of that role is something astronomers are still figuring out. Today, they’re searching the infant Universe, looking for the tiniest, brightest galaxies. That’s because they could help tell the tale of dark matter’s role in galactic creation.

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“Seeing” the Dark Matter Web That Surrounds the Coma Cluster

Artist's impression of Dark matter in the Coma Cluster region. Credit: HyeongHan et al.

According to our predominant cosmological models, Dark Matter makes up the majority of mass in the Universe (roughly 85%). While it is not detectable in visible light, its influence can be seen based on how it causes matter to form large-scale structures in our Universe. Based on ongoing observations, astronomers have determined that Dark Matter structures are filamentary, consisting of long, thin strands. For the first time, using the Subaru Telescope, a team of astronomers directly detected Dark Matter filaments in a massive galaxy cluster, providing new evidence to test theories about the evolution of the Universe.

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