GRBs are the most powerful energy releases since the Big Bang and are so bright that they rival the whole Universe in luminosity. They last for a very short time, from less than a second to a few minutes. In order to emit such incredible power in so little time, the exploding material must be moving at a speed comparable with that of light, which is 300,000 km per second.
The initial readings for two such GRBs were recorded by a satellite gamma-ray telescope orbiting the Earth, on 18 April and on 7 June 2006. In a matter of a few seconds, their position was transmitted to the ground, and the robotic 'REM' Telescope at the European Southern Observatory (ESO; La Silla, Chile) began to observe these GRB fields, detecting near-infrared afterglows and monitoring the evolution of their luminosity as a function of time (the light curve).
The two gamma-ray bursts were located in far-away galaxies, at 9.3 and 11.5 billion light-years respectively. For both events, the light curve was initially rising, then reached a peak, and eventually started to decline, as it is expected for GRB afterglows. The peak is, however, only rarely detected. Its determination is very important and very exciting, since it allows a direct measurement of the expansion velocity of the explosion.
"The burst of 7 June 2006 exploded when we were at a GRB Conference in Venice. When we looked at the first data and saw that the light curve was rising, we were so excited that we performed the data reduction in real time. As a result, the afterglow light curve could be shown at the conference just a few hours later" recalls Susanna Vergani (postgraduate student, DCU-DIAS).
For both bursts, the velocity turns out to be very close to the speed of light, to be precise 99.9997% of this value. Astronomers use a special number, called Lorentz factor, to express these high velocities. Objects moving much slower than light have a Lorentz factor of about 1, while for these two GRBs it is about 400.
"This is an important result, which confirms the 'fireball' theory that has been put forward to explain these exceptional explosions and, interestingly, has been achieved with a small-size telescope" says Prof. Evert Meurs, Director of Dunsink Observatory and leader of the Irish team involved in this project.
Shane Kenny | alfa
Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz
New functional principle to generate the „third harmonic“
16.02.2017 | Laser Zentrum Hannover e.V.
In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport
Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...
The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.
The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...
Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...
Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".
Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...
13.02.2017 | Event News
10.02.2017 | Event News
09.02.2017 | Event News
17.02.2017 | Medical Engineering
17.02.2017 | Medical Engineering
17.02.2017 | Health and Medicine