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Supernova Spotting
Poziom:
Temat: Nauka i technologia
The control room of the ESO Very Large Telescope
at Paranal. Here, astronomers observe the
sky, using the advanced capabilities of this
high- tech installation in the Chilean Atacama
desert. With great expertise scientists and
telescope operators master the VLT controls
and make the difficult observations appear
routine. But suddenly an alarm rings and calls
for their undivided attention.
Now because the optical afterglow of a gamma
ray burst fades extremely rapidly, the observations
must start as soon as possible after the initial
discovery of the burst. And the VLT can deal
with such time-critical observations better
than any other telescope.01:31 [Narrator]
Gamma ray bursts are the most powerful explosions
in the universe. Astronomers do not fully
understand their origin, but they are thought
to be caused by incredibly energetic events
such as the collapse of massive stars.
Gamma ray bursts are so energetic, that, for
a brief instant, they outshine the rest of
their entire galaxy. They produce more energy
in a few seconds than the Sun will in its
whole lifetime. After the flash of gamma-rays
has ended, an optical afterglow can usually
be detected for a few hours. Astronomers look
at this to learn more about how and why gamma
ray bursts occur.
Because gamma ray bursts typically occur at
a very large distance from Earth, their afterglow
is faint. In addition, the afterglow fades
very rapidly, so that within a few hours it
can be up to 500 times fainter still. Hence,
in order to learn more about the nature of
a gamma ray burst and the influence of the
explosion on its surroundings, the event must
be observed as quickly as possible.
The VLT is perfectly equipped to obtain high-
resolution observations of a Gamma Ray Burst.
But before it can do so, such a burst must
first be discovered. The Swift satellite chases
gamma ray bursts with its wide-field Burst
Alert Telescope. Once a burst has been discovered
and verified, it is immediately reported to
the VLT and other observatories.
An alarm at the VLT console indicates to the
astronomers that the activation of the Rapid
Response Mode has been requested.
The scientists have to confirm that the VLT
unit telescope can be moved safely, and within
seconds all on-going observations are stopped.
Then the system performs robotic observations
without any human intervention, except for
the alignment of the spectrograph slit. This
automated procedure guarantees quick and accurate
observations. In fact, the VLT allows astronomers
to begin observations within only a few minutes
of detection by Swift. With events as short-lived
as these, this can mean the difference between
making high quality observations and seeing
nothing at all.
But the VLT at Paranal Observatory is not
the only ESO installation which carries out
gamma ray burst observations. At the La Silla
observatory there are also telescopes that
can observe these events.
The 2.2-metre MPG/ESO telescope features the
GROND instrument which takes images of the
afterglow simultaneously in seven different
colours,. And that gives astronomers further
insights into the physics of gamma ray bursts.
In addition, there are two smaller telescopes,
the 60 cm REM and the 25 cm TAROT and these
are also located at La Silla. These robotic
telescopes are designed to react immediately
when they receive an alert on a gamma ray
burst, making it possible to start observing
the burst within seconds.
Scientists agree that gamma ray bursts are
associated with the formation of black holes,
but until now the exact nature of the bursts
remains enigmatic and more high-resolution
spectroscopy data is needed.
The VLT offers enormous light collecting power
and high resolution. In addition it is equipped
with a suite of high-tech instruments. It
is the combination of the VLT's enormous observational
potential with ultra fast response times,
which provides data of superb quality to the
scientists who study gamma ray bursts.
The Rapid Response Mode at the VLT will be
triggered many more times in the future, and
ESO will continue to collect first class data
on gamma ray bursts - data which will perhaps
one day help to unravel the secrets of the
most energetic explosions in the universe.
This is Dr J signing off for the ESOcast.
Join me again next time for another cosmic
adventure
