In December 1997 the Dutch/Italian BeppoSAX-satellite registered the strongest explosion ever observed in the universe. Immediately after that the Keck telescope in Hawaii observed it for further investigation. During the few seconds of the outburst, the same amount of energy was released as is transmitted by our milkyway galaxy during hundreds of centuries.
Fireworks at the edge of the universe.
The
explosion took place near the border of the visible part of the universe.
We noticed this because of a very short gamma burst, which is a gigantic outburst of
gamma radiation.
This is a type of electromagnetic radiation at a very high energy level.
For thirty years we have realized that every now and then
gamma bursts occur, coming from directions in the universe, but their
origin is still unknown. The bursts usually only last for a few seconds and at most half a minute.
Determining the location.
In May 1997 for the first time scientist managed to locate such a gamma ray
burst in the sky. The determination of its distance was possible because
gamma ray bursts still glow for several days after the initial explosion. They transmit röntgen radiation,
visible light, and radio waves. Unlike the gamma ray radiation
itself, which is absorbed by the Earth's atmosphere, these other forms of radiation
are observable by large telescopes on Earth like the herschel telescope
at La Palma and sometimes even with radio telescopes.
As
soon as the gamma ray burst is located by a satellite, these telescopes
aim at the little glowing point, and subsequently search
for a galaxy at exactly the same location. The distance of such distant
galaxies can be determined pretty accurately, and it is assumed
that the gamma ray burst must have came from that same location also.
The observation of such a distant galaxy requires the use a large telescopes, such
as the Keck-II telescope in Hawaii. It is as difficult to trace these bursts as seeing a 100-Watt lamp
at a distance of 1.5 million kilometers.
Still in 1997 it scientists determined that gamma ray bursts
are billions of lightyears away.
Gigantic amounts of energy.
Even though they appear to be so very distant, enormous quantities of energy
must have been released to cause a gamma ray burst that would reach
Earth from so far away. It must have been a huge explosion
that took place in the very distant past: after all the radiation and the light
ihas been traveling through space for billions of years before reaching Earth.
The burst of light itself must have occured at the the same time or a few
milliseconds after the Big Bang.
According to Einstein's
most famous formula E=mc2,
matter is equivalent to a lot of energy. Even during the explosion of a
large nuclear bomb only a few grams of matter is transformed into heat
and radiation energy. Gamma ray bursts sometimes tranasform the equivalent of
50,000 Earth masses at onceinto pure energy.
Still today it is not known how this is possible, perhaps it is a collision
between neutronen stars and
blackholes. However according
to the commonly accepted theories, even a collision between two neutron stars
would not produce such a tremendous amount of energy. The only way theoretically possible is if the gamma rays
are transmitted as double cones, which would casue the röntgen radiation
of a pulsar to be observed only if it happens to point toward Earth. In such
a case the total energy is about 10 to 100 times less, compared to a gamma ray
burst that emits the same intensity in all directions. Such levels
of energy are somewhat possible with the collision of two neutron stars.
Until now however, there are no signs that would indicate that gamma radiation
is emitted in cone-shaped bundles, which means that we are
talking about unimaginable amounts of energy.
So, scientists have not found the solution to this riddle yet, perhaps it is caused by
a completely new and unknown phenomena!
images from Adzaterdag 1997