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This whirling image features a bright spiral galaxy known as MCG-01–24-014, which is located about 275 million light-years from Earth. In addition to being a well-defined spiral galaxy, MCG-01–24-014 has an extremely energetic core known as an active galactic nucleus (AGN) and is categorized as a Type-2 Seyfert galaxy.

Seyfert galaxies, along with quasars, host one of the most common subclasses of AGN. While the precise categorization of AGNs is nuanced, Seyfert galaxies tend to be relatively nearby and their central AGN does not outshine its host, while quasars are very distant AGNs with incredible luminosities that outshine their host galaxies.

There are further subclasses of both Seyfert galaxies and quasars. In the case of Seyfert galaxies, the predominant subcategories are Type-1 and Type-2. Astronomers distinguish them by their spectra, the pattern that results when light is split into its constituent wavelengths. The spectral lines that Type-2 Seyfert galaxies emit are associated with specific ‘forbidden’ emission lines. To understand why emitted light from a galaxy could be forbidden, it helps to understand why spectra exist in the first place.

ESA’s Euclid mission is on a quest to unveil the nature of two elusive ‘dark’ entities. As the renowned theoretical physicist Stephen Hawking remarked in 2013, “The missing link in cosmology is the nature of dark matter and dark energy”

During the last 70 years, scientists have made enormous progress in understanding the very initial phases of the Universe and its evolution to the present day. Thanks to advances in observations and theoretical modelling, a clear picture has emerged of how stars form, and how galaxies grow and interact with each other, coming together to form groups and clusters.

Continue reading “Euclid: Gate to the dark” »

A universe that continually expands has long been the dominant cosmological framework. But a universe that undergoes cycles of expansion and contraction, perhaps for all time, has recently been analyzed mathematically, and its proponents claim that it provides a more convincing cosmological paradigm. Join leaders of this renegade approach as they make the case for a new kind of cosmology that reimagines time.

The Big Ideas Series is supported in part by the John Templeton Foundation.

Continue reading “Was the Big Bang the Beginning? Reimagining Time in a Cyclic Universe” »

The death of cosmology in an age of chaos.

The new tension, centered around a value for cosmic lumpiness known as S8, could join the Hubble tension in dethroning our best picture of how the universe evolved.

SN 1,006, a supernova observed over a millennium ago, has been extensively studied using NASA ’s Chandra and IXPE telescopes, revealing critical details about its magnetic field and particle acceleration, contributing to our understanding of cosmic rays.

When the object now called SN 1,006 first appeared on May 1, 1006 A.D., it was far brighter than Venus and visible during the daytime for weeks. Astronomers in China, Japan, Europe, and the Arab world all documented this spectacular sight, which was later understood to have been a supernova. With the advent of the Space Age in the 1960s, scientists were able to launch instruments and detectors above Earth’s atmosphere to observe the Universe in wavelengths that are blocked from the ground, including X-rays. The remains of SN 1,006 was one of the faintest X-ray sources detected by the first generation of X-ray satellites.

Recent observations with nasa’s x-ray telescopes.

In 2022, scientists from Northwestern University presented novel observational data indicating that long gamma-ray bursts (GRBs) might originate from the collision of a neutron star with another dense celestial body, such as another neutron star or a black hole — a finding that was previously believed to be impossible.

Now, another Northwestern team offers a potential explanation for what generated the unprecedented and incredibly luminous burst of light.

Continue reading “Scientists Propose New Explanation for ‘Impossible’ Gamma-Ray Burst” »

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Continue reading “The Boundary Between Black Holes & Neutron Stars” »

Observing these types of stars is rare; only one was previously identified. Now, researchers have found a whole population of these stars in the Large and Small Magellanic Clouds, relatively nearby satellite galaxies of the Milky Way. The finding may give insight into hot helium stars, which are thought to be the start of neutron star mergers and hydrogen-poor core-collapse supernovae. The study was published this month in Science.

“Our work sheds light on these fascinating relationships, revealing a universe that is far more interconnected and active than we previously imagined,” says Bethany Ludwig, a PhD candidate at the University of Toronto and coauthor of the study, in a press release. “Just as humans are social beings, stars too, especially the massive ones, are rarely alone.”

In 2015, the LIGO/Virgo experiment, a large-scale research effort based at two observatories in the United States, led to the first direct observation of gravitational waves. This important milestone has since prompted physicists worldwide to devise new theoretical descriptions for the dynamics of blackholes, building on the data collected by the LIGO/Virgo collaboration.

Researchers at Uppsala University, University of Oxford, and Université de Mons recently set out to explain the dynamics of Kerr black holes, theoretically predicted black holes that rotate at a constant rate, using theory of massive high-spin particles. Their paper, published in Physical Review Letters, specifically proposes that the dynamics of these rotating black holes is constrained by the principle of gauge symmetry, which suggests that some changes of parameters of a physical system would have no measurable effect.

“We pursued a connection between rotating Kerr black holes and massive higher-spin particles,” Henrik Johansson, co-author of the paper, told Phys.org. “In other words, we modeled the black hole as a spinning fundamental particle, similar to how the electron is treated in quantum electrodynamics.”