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Scientists untangle mysteries of gamma-ray bursts — the cosmos’s most powerful explosions

Wednesday July 17, 2024 11:30 am

Researchers may be a step closer to ascertaining how gamma-ray bursts are among the most powerful explosions in the known universe. For context, a single gamma-ray burst (GRB) can produce far more energy within seconds than the sun will radiate in billions of years. Because of this massive power, experts hypothesize that GRBs are created by some of the universe’s most violent events. This includes events like supernova explosions that mark the deaths of colossal stars and the collision and merger of two neutron stars (“dead” stars composed of the densest matter we know of), plus outbursts from baby black holes.

The facets of these blasts still remain veiled in mystery, including the exact mechanism that launches a gamma-ray burst and what exactly causes a “long” GRB that lasts more than 2 seconds as opposed to a “short” GRB that lasts for less time. One team of researchers from the Huntsville-based University of Alabama, for instance, has been studying the light emissions of gamma-ray bursts and how they change over time to better model these eruptions and finally crack their mysteries.

“Despite being studied for over fifty years, the mechanisms by which GRBs produce light are still unknown, a great mystery of modern astrophysics,” team leader Jon Hakkila (a scientist at the University of Alabama in Huntsville), said in a statement. “Understanding GRBs helps us understand some of the most rapid and powerful light-producing mechanisms that Nature employs.” “GRBs are so bright, they can be seen over the breadth of the universe, and — because light travels at a finite velocity — they allow us to see back to the earliest times that stars existed.”

Putting some light on GRBs

One of the primary reasons gamma-ray bursts have remained so hard to comprehend is that theoretical models to describe them have been incapable of explaining the behaviour of their light curves, which are graphs that display how the light intensity of an object changes over time. Further confounding the situation is the fact that no two gamma-ray burst light curves are exactly the same, and the duration of the bursts can last from mere milliseconds to tens of minutes.

Hakkila and associates modelled GRBs as a series of energetic pulses, considering these pulses to serve as the basic units of GRB emission. “They indicate times when a GRB brightens and subsequently fades away. During the time a GRB pulse emits, it undergoes brightness variations that can sometimes occur on very short timescales,” Hakkilastated. “The strange thing about these variations is that they are reversible in the same way [palindrome] words like ‘rotator’ or ‘kayak’ are reversible.”The scientist added that it is very tough to understand how this reversibility can be the case because, contrasting the letters in a word, time can only be read in one direction.”The mechanism that produces light in a GRB pulse somehow produces a brightness pattern, then subsequently generates this same pattern in reverse order,” he said. “That is pretty weird, and it makes GRBs unique.”

Extraterrestrial Life in Cosmos? James Webb Telescope’s Discovery Triggers Alien Investigation

Friday July 12, 2024 11:07 am

Researchers have detected signs of something hidden in the atmosphere that may ultimately prove that life exists somewhere other than Earth.

The James Webb Space Telescope (JWST), the biggest telescope ever sent into space,was launched by NASA in 2021. Since then, we’ve witnessed a whole new perspective on planets, stars and galaxies deeper into the space than humans had ever. But, there are far more pressing concerns that have dogged people for ages: Are we all alone? Is life as we know it a cosmic accident, a one-off event on our distant planet? Is there an abundance of life and perhaps even self-awareness andintellect in the cosmos? Now, science is in a great position to answer them with an incredible leap forward.

As per The Times report published on April 26, the JWST was all set to direct its stare to a far-off planet in a different solar system in order to examine one of the most interesting clues to extraterrestrial life that has ever been found. This follows the discovery of one particular planet by astronomers that was rich in gas that could “only be produced by life.”

This planet called K2-18b is orbiting a Red dwarf star K2-18, which is located beneath the constellation Leo, is roughly half the size of our sun and is too dim to be seen with the naked eye. This planet with a radius around 2.6 times that of Earth is thought to be an ocean-covered globe.

Experts have detected clues of something hidden in the atmosphere that may ultimately prove that life exists somewhere other than Earth. It is known as DMS (dimethyl sulphide), a gas. The gas has a single source on Earth. According to the National Aeronautics and Space Administration, it is “only produced by life,” mostly by “phytoplankton in marine environments.”

DrNikkuMadhusudhan (the study’s lead astrophysicist from Cambridge) told the British newspaper that while the scientists could say with more than 50% confidence that dimethyl sulphide was present based on preliminary data returned by the James Webb Space Telescope last year, this is far from “conclusive evidence.”

He was to hold off until the telescope’s eight hours of scheduled observations on Friday when it was going to look especially for DMS. Before he can confidently announce that it has been located, he will next spend months going through the data, according to The Times.

Despite their superlative efforts, researchers have been unable to come up with a natural geological or chemical mechanism that may produce DMS in the absence of living beings.

K2-18b is 124 light-years from Earth. By galactic standards, this makes it our close neighbour, nevertheless, it would take a probe 2.2 million years to reach there at the Voyager spacecraft’s speed (38,000 mph).

Thermodynamics used to describe expansion of the cosmos

Wednesday July 10, 2024 11:00 am

The perception that the universe is expanding dates from nearly a century ago. It was first put forth by Belgian cosmologist Georges Lemaître (1894–1966) way back in 1927 and confirmed observationally by American astronomer Edwin Hubble (1889-1953) just two years later. Hubble observed that the redshift in the electromagnetic spectrum of the light received from cosmic objects was directly proportional to their distance from us, which effectively meant that bodies farther away from us were moving away faster and the cosmos must be expanding.

A startling new ingredient was added to the model in 1998 when observations of very far away supernovae by the Supernova Cosmology Project and the High-Z Supernova Search Team revealed that the expansion of universe is speeding up, rather than slowing down due to gravitational forces, as had been supposed. This discovery led to the idea of dark energy, which is believed to account for more than 68% of all the energy in the presently observable universe, while ordinary matter anddark matter account for about 5% and 27% respectively.

“Measurements of redshift suggest that the accelerating expansion is adiabatic [without heat transfer] and anisotropic [varying in magnitude when measured in different directions],” said Mariano de Souza (a professor in the Department of Physics at São Paulo State University (UNESP) in Rio Claro, Brazil). “Fundamental concepts in thermodynamics allow us to infer that adiabatic expansion is always accompanied by cooling due to the barocaloric effect [pressure-induced thermal change], which is quantified by the Grüneisen ratio [Γ, gamma].”

In 1908, German physicist Eduard August Grüneisen (1877–1949) offered a mathematical expression for Γeff, the effective Grüneisen parameter, a key quantity in geophysics that often occurs in equations describing the thermoelastic conduct of material. It combines three physical properties: expansion coefficient, isothermal compressibilityand specific heat.

Nearly a century later, in 2003, Lijun Zhu and collaborators showed that a specific part of the Grüneisen parameter called the Grüneisen ratio, defined as the ratio of thermal expansion to specific heat, increases considerably in the vicinity of a quantum critical point owing to the buildup of entropy. In 2010, Souza and two German collaborators demonstrated that the same thing happens near a finite-temperature critical point.

Now Souza and fellow scientists at UNESP have used the Grüneisen parameter to describe tricky aspects of the expansion of the cosmos in an article published in the journal Results in Physics, presenting part of the Ph.D. research of first author Lucas Squillante, presently a postdoctoral fellow under Souza’s supervision.

“The dynamics associated with the expansion of the universe are generally modeled as a perfect fluid whose equation of state is ω = p/ρ, where ω [omega] is the equation of state parameter, p is pressure, and ρ [rho] is energy density. Although ω is widely used, its physical meaning hadn’t yet been appropriately discussed. It was treated as merely a constant for each era of the universe. One of the important results of our research is the identification of ω with the effective Grüneisen parameter by means of the Mie-Grüneisen equation of state,” Souza stated.


Wednesday July 3, 2024 9:33 am

New research offers some indications that the universe is filled with particles adept at traveling faster than lightand that this scenario holds up as a potentially “viable alternative” to our existing cosmological model.The idea is a little bit far-fetched, sure, but it’s worthy of being heard out. These hypothetical particles, termed tachyons, aren’t likely to be real — but they’re definitely not some hokey bit of sci-fi, either. The potential for their presence is something physicists have been giving serious thought for many decades, raising fundamental queries about the nature of causality.

As detailed in a still-to-be-peer-reviewed study, the researchers postulate that tachyons are the building blocks of dark matter, an unobservable — and in spite of being widely considered to exist by scientists, technically hypothetical — substance that is believed to account for about 85 percent of all matter in the cosmos.Because we can only observe dark matter’s substantial gravitational effect, we don’t know what it really is, leaving the door open to all kinds of likelihoods that are worth considering.

Growing Problem

As it turns out, a tachyon-filled universe does quite a great job of explaining the cosmos’s ongoing expansion, according to the researchers.In the standard cosmological model, the presence of so-called dark energy is used to explain the expansion of the cosmos. Also unobservable, dark energy is believed to dwarf even dark matter, accounting for up to 70 percent of the entire cosmos.Without it, the sheer gravity of all the mass in the cosmos would finally slow down its expansion. Instead, researchers have observed the rate of expansion is in fact accelerating — driven by, it’s hypothesized, dark energy.

But if tachyons are real and encompass the cosmos as dark matter, they could also potentially explain this acceleration. The scientists found that, in such a set-up, tachyonic dark matter would initially slow down the universe’s expansion, before reversing and causing it to accelerate like we see now. They call this an “inflected” expansion.

Imperfect Match

So far, their proof to support this comes from observations of Type Ia supernovae in which a dying star collapses and explodes — caused in some types of binary star systems.These distinct supernovae are known as standard candles (cosmic objects with a known luminosity that let astronomers to use as a reference point to calculate distances in space). It was by utilizing Type Ia supernovae as standard candles, actually, that researchers first confirmed that the expansion of the cosmos was accelerating.

When the scientists compared their tachyonic model to sample data from the Type Ia supernovae, they discovered that the two are “comfortably consistent with one another.”Obviously, this is a very limited application of the model. It raises intriguing prospects for follow-up research, sure, but it’s a far cry from proving that tachyons in fact exist. Nevertheless, it shows just how much we have left to learn about the fundamental phenomena that govern the universe.

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