Tip Sheet

April Meeting 2024

Simulations May Explain Formation and Arrangement of Satellite Galaxies Around the Milky Way
April 3, 1:42-1:54 p.m. PT, Ballroom A4

Faint, satellite galaxies like those that orbit the Milky Way form in clumps of dark matter, giving researchers an opportunity to study the evolution of dark matter structure in the universe and test cosmological theories like the cold dark matter model. The cold dark matter model has historically faced challenges in explaining some aspects of observed satellite galaxies, but new simulations have replicated structures of satellite galaxies around a larger galaxy like those seen around the Milky Way. The simulations also predict the formation of the most massive satellite galaxies, like the Large Magellanic Cloud orbiting the Milky Way. The presence of the Large Magellanic Cloud may even help explain why the Milky Way’s satellites orbit in a thin, planar arrangement.

A Low-Mass Brown Dwarf that Pushes the Boundaries Between These Objects and Gas Giant Planets
April 3, 5:21-5:33 p.m. PT, Ballroom B2

Among brown dwarfs — objects in between small stars and large gas planets — a class known as Y dwarfs is especially low-mass and low-temperature, at times overlapping in properties with some giant exoplanets. New data confirms that a nearby brown dwarf only 6-8 parsecs away is a Y dwarf. Researchers estimate that this Y dwarf is only about 4 to 6 times Jupiter’s mass. The mass estimate puts this Y dwarf well within the mass range of gas giant exoplanets, suggesting that this object is particularly worthy of follow-up study to better understand these strange objects and their boundaries with gas giant planets.

What We Should See If Black Holes are the Explanation for Dark Energy
April 3, Poster Session I (5:30-7:30 p.m. PT), Exhibit Hall A

Some researchers recently suggested the hypothesis that a particular kind of black hole might be responsible for dark energy, the forces that lead the universe’s expansion to accelerate. A team has now explored this hypothesis, spelling out what observable effects researchers should expect to see if this were the case. The team found many observable implications that would result if black holes are the source of dark energy — there should be many more black hole mergers than currently observed by gravitational wave detectors such as LIGO, and the masses of these merging black holes should be larger and that the supermassive black holes in matter-deficient elliptical galaxies should be rotating slowly.

How Collisions Shape Stellar Populations in the Galaxy’s Center
April 4, 12:21-12:33 p.m. PT, Ballroom A4

The Milky Way harbors a supermassive black hole at its center, surrounded by a dense cluster of stars. In this region, many stars will collide with another star at least once during their lifetime. Using statistical methods, researchers investigated the effects of these collisions on the properties of stellar populations in the Galactic center. The researchers found that within a distance of just 0.01 parsecs from the supermassive black hole, for instance, destructive collisions can halve the stellar population within one billion years. These destructive collisions can also result in a population of strange, low-mass stars throughout the Galactic center: stars lose their outer layers in a destructive collision near the supermassive black hole before migrating to the outer region of the cluster, where they can survive and continue to evolve. Collisions outside of 0.01 parsecs lead to mergers. In certain cases, stars like our Sun can experience many collisions and mergers and go on to become massive stars, including those ten times the Sun’s mass. These merger products can masquerade as rejuvenated, young-looking stars, when in fact they formed through collisions from an older population.

Cool, Bright, Variable Stars in Nearby Satellite Galaxies May Be Key to Understanding When Stars Explode as Supernovae
April 4, 4:21-4:57 p.m. PT, Ballroom B10

While probing the identity of a mysterious star in one of the small satellite galaxies near the Milky Way, researchers identified a potential population of another important class of stars. The researchers studied the properties of HV2112, a star in the Small Magellanic Cloud that some say may be the first compelling candidate for a Thorne-Żytkow Object — a cool, bright star with a neutron star at its core. They searched for other cool, bright stars with similar properties in nearby satellite galaxies and identified several more candidates. Upon analyzing these candidate objects, they found that many of the stars’ properties are consistent with those of massive asymptotic giant branch (AGB) or super-AGB stars. The researchers suggest that this may be the first identified population of super-AGB stars — stars that represent the tipping point between massive stars that explode as supernovae and low-mass stars that do not, making them key to better understanding when stars do and do not explode as supernovae.

Evidence for Nitrogen-9, an Exotic, Proton-Rich Atomic Nucleus
April 4, 4:57-5:33 p.m. PT, Ballroom B2

Generally, light atomic nuclei are more stable when they have similar numbers of neutrons and protons, and nuclei with more protons than neutrons can have exotic properties. Researchers present evidence for nitrogen-9, an extremely proton-rich isotope of nitrogen with seven protons and two neutrons in its nucleus. Nitrogen-9’s nucleus is thought to consist of a bound set of two neutrons and two protons surrounded by a cloud of five unbound protons. This would be the first known example of a nucleus that can emit five protons from its ground state — a nucleus’s lowest energy state — as opposed to from an excited state.

A Proposed Explanation for the ‘Zebra’ Radio Emission Pattern From the Crab Pulsar
April 5, 6:18-6:30 a.m. PT, Virtual Room 03

The Crab Pulsar, a neutron star that remains from a supernova explosion seen on Earth in the year 1054, produces high-energy radio emission whose spectrum has a strange, zebra-like pattern. But for more than 15 years, theoretical studies have not come up with a satisfactory mechanism to explain the strange radio emission. A team of researchers now proposes a model to explain the zebra-patterned radio emission, contributing to researchers’ understanding of pulsars.

Generating Artificial Gravity for Long-Distance Space Travel with High-Frequency Oscillations
April 5, Poster Session II (2-4 p.m. PT), Exhibit Hall A

Producing sources of artificial gravity may be a necessary part of planning longer-distance crewed space missions, such as a mission from Earth to Mars, to mitigate the negative effects of low gravity on the human body. Rotating parts of a spacecraft to generate centrifugal force is one proposed source of artificial gravity, but this method can have its own drawbacks. A team of researchers has proposed an alternative method of generating a centrifugal force by using high-frequency, small-amplitude oscillating vibrations. The researchers are currently working on designing an apparatus to demonstrate this method of producing a centrifugal force as an artificial source of gravity.

An Experiment That Searched for Ultralight Bosonic Dark Matter Signs in State Parks
April 5, Poster Session II (2-4 p.m. PT), Exhibit Hall A

Earth and its ionosphere could transform ultralight bosonic dark matter, a hypothetical kind of dark matter, into magnetic fields that oscillate in specific patterns across Earth’s surface. Researchers share results from the Search for Non-Interacting Particles Experimental (SNIPE) Hunt, a project that used magnetometers placed in remote areas in California, Ohio, and Pennsylvania away from sources of human-caused magnetic interference, such as state parks, to search for these telltale magnetic field patterns. The researchers constrained properties of these hypothetical varieties of dark matter and plan to expand a future search to target a different range of frequencies.

Possible Shielding Methods to Protect Interplanetary Travelers on a Potential Mission to Mars
April 5, 4:33-4:45 p.m. PT, Ballroom B5

A crewed mission from Earth to Mars would need to protect human travelers from dangers such as energetic cosmic ray radiation, the impacts of low gravity on the body, and the potential risks of high-velocity micrometeoroids. A team of researchers is working on spacecraft concepts to protect travelers from these threats. The researchers have proposed an approach that uses both a passive shielding effect, from combinations of materials that attenuate electromagnetic radiation, and an active shielding effect, in which a magnetic field deflects charged particles, and developed computational methods to evaluate the efficacy of the shielding methods.

Running for State Office as a Physicist
April 6, 5:30-5:42 a.m. PT, Virtual Room 01

Ramón Barthelemy, a professor of physics education research at the University of Utah, is running for a Utah state house representative position, citing advocacy for equitable science education environments as a motivation. He will discuss his campaign and his plans to use his platform to support science education and encourage other physicists to run for positions in their state legislatures.

New Measurement of the Hubble Constant Using JWST Observations
April 6, 1:57-2:24 p.m. PT, Ballroom A1

Measurements of the Hubble constant — a parameter describing the expansion of the universe — that teams of researchers have made via a method relying on variable stars and supernovae and a method relying on the cosmic microwave background have differed significantly from one another. If this discrepancy, known as the Hubble tension, persists, it could indicate new physics beyond the standard model. Researchers now present new results from James Webb Space Telescope observations designed to reduce systematic uncertainties in measurements of the Hubble constant using three independent means of measuring local distances and supernovae that directly bear on the Hubble tension.

Better Constraining Dark Matter Properties with Ultra-Faint and Compact Galaxies
April 6, 4:09-4:21 p.m. PT, Ballroom B2

In recent years, researchers have identified several extremely faint groups of stars orbiting the Milky Way that may be the faintest and most compact galaxies known. If researchers can confirm that these ultra-faint compact stellar systems are dark matter-dominated, that would make them an ideal place to look for evidence of dark matter annihilation. A team has now analyzed more than 14 years of data from the Fermi Gamma-Ray Space Telescope that coincided with 26 of these ultra-faint systems. The researchers found no evidence for extra gamma-ray emission from potential dark matter annihilation reactions in these systems, but they showed that these ultra-faint objects allow them to place constraints on dark matter properties that are comparable to or even stricter than those placed by studies of dwarf spheroidal galaxies. The results suggest that further characterizing these ultra-faint objects may be an important target for researchers seeking to better constrain dark matter properties.