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Category: cosmology – Page 119

The mini-halos of dark matter scattered throughout the cosmos could function as highly sensitive probes of primordial magnetic fields. This is what emerges from a theoretical study conducted by SISSA and published in Physical Review Letters.

Present on immense scales, magnetic fields are found everywhere in the universe. However, their origin is still a subject of debate among scholars. An intriguing possibility is that magnetic fields originated near the birth of the universe itself; that is, they are primordial magnetic fields.

In the study, the researcher showed that if magnetic fields are indeed primordial then it could cause an increase in dark matter density perturbations on small scales. The ultimate effect of this process would be the formation of mini-halos of dark matter, which, if detected, would hint towards a primordial nature of magnetic fields. Thus, in an apparent paradox, the invisible part of our universe could be useful in resolving the nature of a component of the visible one.

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A team of researchers has analyzed more than one million galaxies to explore the origin of the present-day cosmic structures, reports a recent study published in Physical Review D as an Editors’ Suggestion.

Until today, precise observations and analyses of the cosmic microwave background (CMB) and large-scale structure (LSS) have led to the establishment of the standard framework of the universe, the so-called ΛCDM model, where cold dark matter (CDM) and dark energy (the cosmological constant, Λ) are significant characteristics.

This model suggests that primordial fluctuations were generated at the beginning of the universe, or in the early universe, which acted as triggers, leading to the creation of all things in the universe including stars, galaxies, galaxy clusters, and their spatial distribution throughout space. Although they are very small when generated, fluctuations grow with time due to the gravitational pulling force, eventually forming a dense region of dark matter, or a halo. Then, different halos repeatedly collided and merged with one another, leading to the formation of celestial objects such as galaxies.

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In a public lecture titled “The Meaning of Spacetime,” renowned physicist Juan Maldacena outlined ideas that arose from the study of quantum aspects of black holes.

V/ Perimeter Institute

On July 27, Juan Maldacena, a luminary in the worlds of string theory and quantum gravity, will share his insights on black holes, wormholes, and quantum entanglement.

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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.

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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.

Yet, fundamental mysteries remain. 95% of the Universe appears to be made up of unknown ‘dark’ matter and energy. Dark matter and energy affect the motion and distribution of visible sources but do not emit, reflect or absorb any light. And scientists do not know what these dark entities actually are.

To address this question, Euclid will create a great map of the large-scale structure of the Universe across space and time by observing with unprecedented accuracy billions of galaxies out to 10 billion light-years. This is not easy, and making sure that Euclid is up to the task has required the expertise and dedication of many people over several years of work.

This video captures the journey behind the Euclid mission, from a human and intensely visual perspective. It shows tiny screws, winding cables and shiny surfaces in a whole new light, revealing how each piece comes together to form the space telescope. Be drawn in by awe-inspiring photos of the cosmos, and stay for the seemingly choreographed ballet of teamwork necessary to assemble and test the spacecraft, before being swept away by the emotion of the launch into space.

Euclid’s adventure has begun. With its observations during the coming years, it will help us uncover the missing link in cosmology and open the gate to the ‘dark’ side of the Universe.

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.

Participants:
Peter Galison.
Anna Ijjas.
Paul Steinhardt.

Moderator:
Brian Greene.

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

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.

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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.

After developing the first numerical simulation that follows the jet evolution in a black hole — neutron star merger out to large distances, the astrophysicists discovered that the post-merger black hole can launch jets of material from the swallowed neutron star.

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