Lifeboat Foundation

Large, low-background detectors using xenon as a target medium are widely used in fundamental physics, particularly in experiments searching for dark matter or studying rare decays of atomic nuclei. In these detectors, the weak interaction of a neutral particle—such as a neutrino—with a xenon-136 nucleus can transform it into a cesium-136 nucleus in a high-energy excited state.

The gamma rays emitted as the cesium-136 relaxes from this excited state could allow scientists to separate rare signals from background radioactivity. This can enable new measurements of solar neutrinos and more powerful searches for certain models of dark matter. However, searching for these events has been difficult due to a lack of reliable nuclear data for cesium-136. Researchers need to know the properties of cesium-136’s excited states, which have never been measured for this isotope.

This research, appearing in Physical Review Letters, provides direct determination of the relevant data by measuring gamma-ray emission from cesium-136 produced in nuclear reactions at a particle accelerator. Importantly, this research reveals the existence of so-called “isomeric states”—excited states that exist for approximately 100ns before relaxing to the ground state.

Some of the finest, smallest details in the universe – the gaps between elongated groups of stars – may soon help astronomers reveal dark matter in greater detail than ever before. After NASA’s Nancy Grace Roman Space Telescope launches, by May 2027, researchers will use its images to explore what exists between looping tendrils of stars that are pulled from globular clusters. Specifically, they will focus on the tidal streams from globular clusters that orbit our neighboring Andromeda galaxy. Their aim is to pinpoint a greater number of examples of these tidal streams, examine gaps between the stars, and ideally determine concrete properties of dark matter.

Globular cluster streams are like ribbons fluttering in the cosmos, both leading and trailing the globular clusters where they originated along their orbits. Their lengths in our Milky Way galaxy vary wildly. Very short stellar streams are relatively young, while those that completely wrap around a galaxy may be almost as old as the universe. A stream that is fully wrapped around the Andromeda galaxy could be more than 300,000 light-years long but less than 3,000 light-years wide.

With Roman, astronomers will be able to search nearby galaxies for globular cluster stellar streams for the first time. Roman’s Wide Field Instrument has 18 detectors that will produce images 200 times the size of the Hubble Space Telescope’s near-infrared camera – at a slightly greater resolution.

Finally, after more than a decade of work and studying around 1,500 Type Ia supernovas, the Dark Energy Survey has produced a new best measurement of w. We found w = −0.80 ± 0.18, so it’s somewhere between −0.62 and −0.98.

This is a very interesting result. It is close to −1, but not quite exactly there. To be the cosmological constant, or the energy of empty space, it would need to be exactly −1.

Where does this leave us? With the idea that a more complex model of dark energy may be needed, perhaps one in which this mysterious energy has changed over the life of the universe.

It’s not every day astronomers say, “What is that?” After all, most observed astronomical phenomena are known: stars, planets, black holes and galaxies. But in 2019 the newly completed ASKAP (Australian Square Kilometer Array Pathfinder) telescope picked up something no one had ever seen before: radio wave circles so large they contained entire galaxies in their centers.

As the astrophysics community tried to determine what these circles were, they also wanted to know why the circles were. Now a team led by University of California San Diego Professor of Astronomy and Astrophysics Alison Coil believes they may have found the answer: the circles are shells formed by outflowing galactic winds, possibly from massive exploding stars known as supernovae. Their work is published in Nature.

Coil and her collaborators have been studying massive “starburst” galaxies that can drive these ultra-fast outflowing winds. Starburst galaxies have an exceptionally high rate of star formation. When stars die and explode, they expel gas from the star and its surroundings back into interstellar space. If enough stars explode near each other at the same time, the force of these explosions can push the gas out of the galaxy itself into outflowing winds, which can travel at up to 2,000 kilometers/second.

JWST’s recent observations of two quasars from the universe’s infancy reveal crucial insights into the early relationship between black holes and their galaxies, echoing mass ratios seen in the more recent universe.

New images from the James Webb Space Telescope (JWST) have revealed, for the first time, starlight from two massive galaxies hosting actively growing black holes – quasars – seen less than a billion years after the Big Bang. The black holes have masses close to a billion times that of the Sun, and the host galaxy masses are almost one hundred times larger, a ratio similar to what is found in the more recent universe. A powerful combination of the wide-field survey of the Subaru Telescope and the JWST has paved a new path to study the distant universe, reports a recent study in Nature.

Observations of giant black holes have attracted the attention of astronomers in recent years. The Event Horizon Telescope (EHT) has started to image the “shadow” of black holes at the galaxy centers. The 2020 Novel Prize in Physics was awarded to stellar motion observations at the heart of the Milky Way. While the existence of such giant black holes has become solid, no one knows their origin.

It’s not every day astronomers say, “What is that?” After all, most observed astronomical phenomena are known: stars, planets, black holes, and galaxies. But in 2019 the newly completed ASKAP (Australian Square Kilometer Array Pathfinder) telescope picked up something no one had ever seen before: radio wave circles so large they contained entire galaxies in their centers.

As the astrophysics community tried to determine what these circles were, they also wanted to know why the circles were. Now a team led by University of California San Diego Professor of Astronomy and Astrophysics Alison Coil believes they may have found the answer: the circles are shells formed by outflowing galactic winds, possibly from massive exploding stars known as supernovae. Their work is published in Nature.

The enduring mystery of dark matter has led some physicists to propose that it was forged in a distinct moment of cosmic creation, potentially transforming our view of the early universe.

By Stuart Clark

So the idea is that intergalactic magnetic fields would tend to cluster electrons and ionized intergalactic hydrogen along their field lines, making those regions of the intergalactic voids just slightly denser than the rest of the void. This would cause dark matter to cluster a bit along the field lines as well. The gravitational effect would be extremely tiny, but over the entire history of the Universe, it would add up. So if primordial magnetic fields did form in the early Universe, tendrils of dark matter should be present along the same lines.

In a recent work in Physical Review Letters the authors argue that this effect would produce minihalos of dark matter. Just as galaxies are surrounded by a halo of dark matter due to gravitational clustering, faint halos of dark matter should exist around primordial magnetic field lines to do the gravitational tug of ionized matter along the field lines.

What’s interesting about this idea is that over time the charged ions and electrons would interact with the primordial magnetic fields and tend to cancel them out. The ions and electrons could even merge to create neutral hydrogen, so in the modern Universe, there would be no trace of these early magnetic fields in regular matter. But the microhalos of dark matter would still exist, and they could be seen through the gravitational lensing of distant light sources. These tendrils of dark matter could be the only evidence remaining of the earliest magnetic fields in the cosmos.

A supernova in a nearby galaxy resulted in a compact massive object, providing a link between supernovae, black holes, and neutron stars.