Lifeboat Foundation

An international research team analyzed a database of more than 1000 supernova explosions and found that models for the expansion of the Universe best match the data when a new time dependent variation is introduced. If proven correct with future, higher-quality data from the Subaru Telescope and other observatories, these results could indicate still unknown physics working on the cosmic scale.

Edwin Hubble’s observations over 90 years ago showing the expansion of the Universe remain a cornerstone of modern astrophysics. But when you get into the details of calculating how fast the Universe was expanding at different times in its history, scientists have difficulty getting theoretical models to match observations.

To solve this problem, a team led by Maria Dainotti (Assistant Professor at the National Astronomical Observatory of Japan and the Graduate University for Advanced Studies, SOKENDAI in Japan and an affiliated scientist at the Space Science Institute in the U.S.A.) analyzed a catalog of 1048 supernovae which exploded at different times in the history of the Universe. The team found that the theoretical models can be made to match the observations if one of the constants used in the equations, appropriately called the Hubble constant, is allowed to vary with time.

At the time the proposed planet signal is strongest, stellar activity on the surface of the star was Also strong, says Lubin. Thus, he notes, the signal associated with the planet can be explained by activity emanating from stellar activity instead of from the telltale periodic tug on Barnard’s Star from a putative super-earth.

As I noted here previously, Barnard’s Star, which lies only 6 light years away in Ophiuchus, has long fascinated astronomers both due to its proximity to Earth and the fact that it has the largest apparent motion across our line of sight as any known stellar object. In the 105 years since its discovery by astronomer E.E. Barnard, it is the nearest star to our own Sun in the Northern Celestial Hemisphere, the authors note.

One of the more infamous claims of planets around barnard’s star came in in 1963, when Swarthmore College astronomer Peter van de Kamp announced that he had detected a planet using Swarthmore’s 24-inch refractor at Sproul Observatory. Van de Kamp later updated his findings three more times, proposing a second planet in the system with periods of 12 and 20 years, respectively, the authors note.

New observations and simulations show that jets of high-energy particles emitted from the central massive black hole in the brightest galaxy in galaxy clusters can be used to map the structure of invisible inter-cluster magnetic fields. These findings provide astronomers with a new tool for investigating previously unexplored aspects of clusters of galaxies.

As clusters of galaxies grow through collisions with surrounding matter, they create bow shocks and wakes in their dilute plasma. The plasma motion induced by these activities can drape intra-cluster magnetic layers, forming virtual walls of magnetic force. These magnetic layers, however, can only be observed indirectly when something interacts with them. Because it is simply difficult to identify such interactions, the nature of intra-cluster magnetic fields remains poorly understood. A new approach to map/characterize magnetic layers is highly desired.

Cosmologists love universe simulations. Even models covering hundreds of millions of light years can be useful for understanding fundamental aspects of cosmology and the early universe. There’s just one problem – they’re extremely computationally intensive. A 500 million light year swath of the universe could take more than 3 weeks to simulate… Now, scientists led by Yin Li at the Flatiron Institute have developed a way to run these cosmically huge models 1000 times faster. That 500 million year light year swath could then be simulated in 36 minutes.

Older algorithms took such a long time in part because of a tradeoff. Existing models could either simulate a very detailed, very small slice of the cosmos or a vaguely detailed larger slice of it. They could provide either high resolution or a large area to study, not both.

To overcome this dichotomy, Dr. Li turned to an AI technique called a generative adversarial network (GAN). This algorithm pits two competing algorithms again each other, and then iterates on those algorithms with slight changes to them and judges whether those incremental changes improved the algorithm or not. Eventually, with enough iterations, both algorithms become much more accurate naturally on their own.

Observational evidence of cosmic magnetic fields in a galaxy cluster.

If the authors’ interpretation is correct, it is a remarkable finding, because it implies that relatively strong, ordered magnetic fields (of a few tens of microgauss in strength) exist in the highly disrupted environments of galaxy clusters such as Abell 3376. For comparison, relatively weak magnetic fields (of a few microgauss) have been detected¹³ in the gas at the centres of clusters less disrupted than Abell 3376. So far, it has proved extremely challenging to detect and measure magnetic fields in clusters and in the space between galaxies, and the origin of cosmic magnetic fields is still mysterious. Consequently, any observational evidence for such fields in cluster environments is valuable.

However, there is another plausible explanation for the bent jets, referred to as the slingshot model. In this scenario, MRC 0600‑399 and the nearby radio galaxy are falling back towards the centre of Abell 3376 after being ejected from the centre at supersonic speed. The radio jets of MRC 0600‑399 are bent simply by the pressure of gaseous wind acting in the opposite direction to the galaxy’s motion. Although this alternative model can explain the bent jets, it cannot account for the peculiar double-scythe structures, which suggest that the jets are interacting with a layer of strong, ordered magnetic fields. One limitation of the current work is that the magnetic-field strength in the jet-interaction region was not measured directly but was obtained from numerical simulations.

Continue reading “Black hole jets bent by magnetic fields” »

New observations and simulations show that jets of high-energy particles emitted from the central massive black hole in the brightest galaxy in galaxy clusters can be used to map the structure of invisible inter-cluster magnetic fields. These findings provide astronomers with a new tool for investigating previously unexplored aspects of clusters of galaxies.

As clusters of galaxies grow through collisions with surrounding matter, they create bow shocks and wakes in their dilute plasma. The plasma motion induced by these activities can drape intra–cluster magnetic layers, forming virtual walls of magnetic force. These magnetic layers, however, can only be observed indirectly when something interacts with them. Because it is simply difficult to identify such interactions, the nature of intra-cluster magnetic fields remains poorly understood. A new approach to map/characterize magnetic layers is highly desired.

An international team of astronomers including Haruka Sakemi, a graduate student at Kyushu University (now a research fellow at the National Astronomical Observatory of Japan—NAOJ), used the MeerKAT radio telescope located in the Northern Karoo desert of South Africa to observe a bright galaxy in the merging galaxy cluster Abell 3376 known as MRC 0600–399. Located more than 600 million light-years away in the direction of the constellation Columba, MRC 0600–399 is known to have unusual jet structures bent to 90-degree angles. Previous X-ray observations revealed that MRC 0600–399 is the core of a sub-cluster penetrating the main cluster of galaxies, indicating the presence of strong magnetic layers at the boundary between the main and sub-clusters. These features make MRC 0600–399 an ideal laboratory to investigate interactions between jets and strong magnetic layers.

Scientists are certain that dark matter exists. Yet, after more than 50 years of searching, they still have no direct evidence for the mysterious substance.

University of Delaware’s Swati Singh is among a small group of researchers across the dark matter community that have begun to wonder if they are looking for the right type of dark matter.

Continue reading “Researchers propose repurposing tabletop sensors to search for dark matter” »

Astronomers are hoping to use the wake of stars to test the existing theories of dark matter.

The detection of the axion would mark a key episode in the history of science. This hypothetical particle could resolve two fundamental problems of Modern Physics at the same time: the problem of Charge and Parity in the strong interaction, and the mystery of dark matter. However, in spite of the high scientific interest in finding it, the search at high radio frequency-above 6 GHz-has been almost left aside for the lack of the high sensitivity technology which could be built at reasonable cost. Until now.

The Instituto de Astrofísica de Canarias (IAC) will participate in an international collaboration to develop the DALI (Dark-photons & Axion-Like particles Interferometer) experiment, an astro-particle telescope for dark matter whose scientific objective is the search for axions and paraphotons in the 6 to 60 GHz band. The prototype, proof of concept, is currently in the design and fabrication phase at the IAC. The white-paper describing the experiment has been accepted for publication in the Journal of Cosmology and Astroparticle Physics (JCAP).

Predicted by theory in the 1970’s, the axion is a hypothetical low mass particle that interacts weakly with standard particles such as nucleons and electrons, as well as with photons. These proposed interactions are studied to try to detect the axion with different types of instruments. One promising technique is to study the interaction of axions with standard photons.