scholarly journals Explosions from stellar collapse

2003 ◽  
Vol 212 ◽  
pp. 377-386
Author(s):  
Chris L. Fryer
Keyword(s):  
Potential Energy ◽  
Gravitational Potential ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Power Source ◽  
Gamma Ray Bursts ◽  
Gravitational Potential Energy ◽  
Stellar Collapse ◽  
The Universe

The collapse of a massive star releases a considerable amount of gravitational potential energy. This energy is believed to be the power source of some of the largest explosions in the universe: supernovae, hypernovae, gamma-ray bursts. In this proceedings, we review the mechanisms by which the potential energy from stellar collapse can be tapped to produce these strong explosions, emphasizing how our understanding of massive stars can help constrain these mechanisms.

scholarly journals New mechanism for the cosmological red-shift explaining: non-observation of dark energy, large-number- coincidence and the cosmic coincidence

2015 ◽  
Vol 3 (1) ◽  
pp. 24
Author(s):  
Hasmukh K. Tank
Keyword(s):  
Gravitational Field ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Red Shift ◽  
Relativity Theory ◽  
Gravitational Potential Energy ◽  
Potential Well ◽  
Speed Of Light ◽  
Equivalent Mass ◽  
The Universe

<p>Accepting Einstein’s General Relativity Theory, that the changes in the gravitational field can propagate at the speed of light, it is proposed here that: before an electron in an atom emits a photon, the energy (<em>h f<sub>0</sub></em>) of the photon was a part of total energy of the atom; contributing to establish the gravitational-field around the atom. As soon as an electron in that atom emits a photon of energy <em>h f<sub>0</sub></em>, and the photon starts moving away from the atom, the gravitational-field around the atom partly reduces, proportional to the photon’s energy <em>h f<sub>0</sub></em>, and this wave of ‘reduced gravitational field’ propagates radially-outwards at the speed of light. And a part of energy of the photon gets spent in “filling” the ‘gravitational potential-well’ produced by its energy, when it was a part of energy of the atom. From the derivation presented here we find that the energy spent by the photon to “fill” the ‘gravitational potential-well’, during its inter-galactic journey manifests as the ‘cosmological red-shift’. And the so called ‘total-mass-of-the-universe'’ and ‘radius-of-the-universe'’ are just mathematically-equivalent mass and distance arising while converting electrostatic potential-energy into gravitational potential-energy. This is the reason why we find the large-number-coincidence (LNC). And since there is no expansion of the universe, there is no ‘cosmic coincidence’, that why only in this epoch we find the ‘large-number-coincidence’!</p>

scholarly journals Supernovae and Gamma-ray Bursts

2011 ◽  
Vol 7 (S279) ◽  
pp. 75-82
Author(s):  
Paolo A. Mazzali
Keyword(s):  
Black Hole ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Observational Evidence ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Broad Absorption ◽  
X Ray ◽  
Long Duration

AbstractThe properties of the Supernovae discovered in coincidence with long-duration Gamma-ray Bursts and X-Ray Flashes are reviewed, and compared to those of SNe for which GRBs are not observed. The SNe associated with GRBs are of Type Ic, they are brighter than the norm, and show very broad absorption lines in their spectra, indicative of high expansion velocities and hence of large explosion kinetic energies. This points to a massive star origin, and to the birth of a black hole at the time of core collapse. There is strong evidence for gross asymmetries in the SN ejecta. The observational evidence seems to suggest that GRB/SNe are more massive and energetic than XRF/SNe, and come from more massive stars. While for GRB/SNe the collapsar model is favoured, XRF/SNe may host magnetars.

scholarly journals The Swift satellite lives up to its name, revealing cosmic explosions as they happen

2008 ◽  
Vol 366 (1884) ◽  
pp. 4393-4404 ◽  
Author(s):  
Rhaana L.C Starling
Keyword(s):  
Gamma Radiation ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Electromagnetic Spectrum ◽  
Distant Galaxies ◽  
The 1960S ◽  
Cosmic Explosions ◽  
The Universe

Gamma-ray bursts are the most powerful objects in the Universe. Discovered in the 1960s as brief flashes of gamma radiation, we now know that they emit across the entire electromagnetic spectrum, are located in distant galaxies and comprise two distinct populations, one of which may originate in the deaths of massive stars. The launch of the Swift satellite in 2004 brought a flurry of new discoveries, advancing our understanding of these sources and the galaxies that host them. I highlight a number of important results from the Swift era thus far.

scholarly journals The Life and Death of Massive Stars in the Starburst Galaxy I Zw 18

2015 ◽  
Vol 11 (A29B) ◽  
pp. 215-216
Author(s):  
Dorottya Szécsi ◽  
Norbert Langer
Keyword(s):  
Stellar Evolution ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Starburst Galaxy ◽  
Life And Death ◽  
Long Duration ◽  
Low Metallicity ◽  
The Universe ◽  
Evolution Proceeds

AbstractMassive stars at low metallicity are strong candidates for two of the most energetic explosions in the Universe: long duration gamma-ray bursts and superluminous supernovae. But what is the reason these explosions prefer low metallicity environments? To answer this question, we investigate how massive stellar evolution proceeds in low metallicity environments.

scholarly journals Wind anisotropy and stellar evolution

2008 ◽  
Vol 4 (S255) ◽  
pp. 199-203
Author(s):  
Cyril Georgy ◽  
Georges Meynet ◽  
André Maeder
Keyword(s):  
Angular Momentum ◽  
Massive Star ◽  
Gamma Ray ◽  
Massive Stars ◽  
Gamma Ray Bursts ◽  
Surface Velocity ◽  
Hot Stars ◽  
Low Metallicity ◽  
Determinant Factor ◽  
Fast Rotating

AbstractMass loss is a determinant factor which strongly affects the evolution and the fate of massive stars. At low metallicity, stars are supposed to rotate faster than at the solar one. This favors the existence of stars near the critical velocity. In this rotation regime, the deformation of the stellar surface becomes important, and wind anisotropy develops. Polar winds are expected to be dominant for fast rotating hot stars.These polar winds allow the star to lose large quantities of mass and still retain a high angular momentum, and they modify the evolution of the surface velocity and the final angular momentum retained in the star's core. We show here how these winds affect the final stages of massive stars, according to our knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts rate indicates that our models have too fast rotating cores, and that we need to include an additional effect to spin them down. Magnetic fields in stars act in this direction, and we show how they modify the evolution of massive star up to the final stages.

Research on the Potential Energy-Driving Car with the Function of Avoiding Fixed-Point Obstacles

2012 ◽  
Vol 209-211 ◽  
pp. 2104-2107
Author(s):  
Guang Ming Zou ◽  
Xiu Guang Yang ◽  
Hang Zou ◽  
Chuan Huang ◽  
Jian Feng ◽  
...  
Keyword(s):  
Energy Storage ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Storage System ◽  
Energy Storage System ◽  
Steering System ◽  
Power Source ◽  
Transmission System ◽  
Experimental Result ◽  
Gravitational Potential Energy

An energy storage car driven by gravitational potential energy was designed. The car could avoid the fixed obstacles set on the track when running. It only uses the gravitational potential energy as power source and doesn’t need to use any other forms of power source. The overall design of the car was completed from some aspects of the steering system, energy storage system and transmission system etc. The cam mechanism is to realize steering of the car. Vortex coil spring is to realize the energy storage in the process of weight falling. Transmission system of the car is composed of fixed pulleys, gear mechanisms and the ratchet mechanisms. Experimental result shows that design of the car is reasonable. The design of the car provides guidance significance for the carbon-free car.

Tracker-assisted modelling: simultaneous validation of the conservation law of energy and the work-energy theorem

2021 ◽  
Vol 57 (1) ◽  
pp. 015012
Author(s):  
Unofre B Pili ◽  
Renante R Violanda
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Conservation Law ◽  
Gravitational Potential Energy ◽  
Time Data ◽  
Home Based ◽  
Basic Physics ◽  
Free Falling ◽  
Work Done

Abstract The video of a free-falling object was analysed in Tracker in order to extract the position and time data. On the basis of these data, the velocity, gravitational potential energy, kinetic energy, and the work done by gravity were obtained. These led to a rather simultaneous validation of the conservation law of energy and the work–energy theorem. The superimposed plots of the kinetic energy, gravitational potential energy, and the total energy as respective functions of time and position demonstrate energy conservation quite well. The same results were observed from the plots of the potential energy against the kinetic energy. On the other hand, the work–energy theorem has emerged from the plot of the total work-done against the change in kinetic energy. Because of the accessibility of the setup, the current work is seen as suitable for a home-based activity, during these times of the pandemic in particular in which online learning has remained to be the format in some countries. With the guidance of a teacher, online or face-to-face, students in their junior or senior high school—as well as for those who are enrolled in basic physics in college—will be able to benefit from this work.

scholarly journals Walking in simulated reduced gravity: mechanical energy fluctuations and exchange

1999 ◽  
Vol 86 (1) ◽  
pp. 383-390 ◽  
Author(s):  
Timothy M. Griffin ◽  
Neil A. Tolani ◽  
Rodger Kram
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Gravitational Potential ◽  
Inverted Pendulum ◽  
Mechanical Energy ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Gravitational Potential Energy ◽  
Reduced Gravity

Walking humans conserve mechanical and, presumably, metabolic energy with an inverted pendulum-like exchange of gravitational potential energy and horizontal kinetic energy. Walking in simulated reduced gravity involves a relatively high metabolic cost, suggesting that the inverted-pendulum mechanism is disrupted because of a mismatch of potential and kinetic energy. We tested this hypothesis by measuring the fluctuations and exchange of mechanical energy of the center of mass at different combinations of velocity and simulated reduced gravity. Subjects walked with smaller fluctuations in horizontal velocity in lower gravity, such that the ratio of horizontal kinetic to gravitational potential energy fluctuations remained constant over a fourfold change in gravity. The amount of exchange, or percent recovery, at 1.00 m/s was not significantly different at 1.00, 0.75, and 0.50 G (average 64.4%), although it decreased to 48% at 0.25 G. As a result, the amount of work performed on the center of mass does not explain the relatively high metabolic cost of walking in simulated reduced gravity.

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