An international team of astronomers
using ESO’s Very Large Telescope
has measured the distance to the most remote galaxy so far.
This is the first time that astronomers have been able to confirm
that they are observing a galaxy as it was in the era of reionisation
when the first generation of brilliant stars
was making the young Universe transparent
and ending the cosmic Dark Ages.
This is the ESOcast!
Cutting-edge science and life behind the scenes at ESO,
the European Southern Observatory.
Exploring the ultimate frontier with our host Dr J, a.k.a. Dr Joe Liske.
Hello and welcome to the ESOcast.
In this episode we are going to find out how a team of astronomers
used ESO’s Very Large Telescope, the VLT,
to confirm that a galaxy that had previously been spotted
in images from the NASA/ESA Hubble Space Telescope
is in fact the most distant object that has ever been identified in the Universe.
Studying these first galaxies is extremely difficult.
They are very faint and small
and by the time their dim light gets to Earth
it falls mostly in the infrared part of the spectrum
because it has been stretched by the expansion of the Universe.
To make matters worse, at this very early time,
less than a billion years after the Big Bang,
the Universe was not completely transparent.
It was filled with hydrogen which acted kind of like a fog
and absorbed the ultraviolet radiation from the young galaxies.
So, holding the record for having measured the redshift
of the most distant object in the Universe
is not just a trophy to hang on the wall,
it does have important astrophysical implications.
This is the first time that we’ve managed to obtain spectroscopic observations
of a galaxy from the era of reionisation,
in other words from the time when the Universe
was still clearing out the hydrogen fog.
Despite the difficulties of finding these early galaxies,
the new Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope
discovered several very good candidate objects earlier in 2010.
They were thought to be galaxies shining in the early Universe
at redshifts greater than eight,
but confirming the distances to such faint and remote objects
is an enormous challenge
and can only reliably be done using spectroscopy
from very large ground-based telescopes.
The team was excited to find that
if you combine the huge light collecting power of the VLT,
with the sensitivity of its infrared spectroscopic instrument, SINFONI,
and if you then use a very long exposure time
you just might be able to detect the faint glow
from one of these very remote objects
and then go on to measure its distance.
A 16 hour exposure with the VLT and SINFONI
of the galaxy UDFy-38135539
did indeed show the very faint glow from hydrogen at a redshift of 8.6,
which means that this light left the galaxy
when the Universe was only about 600 million years old.
This is the most distant galaxy ever reliably confirmed.
One of the puzzling things about this discovery
is that the ultraviolet radiation emitted by the galaxy
does not actually seems to be strong enough
to be able to clear out the hydrogen fog around the galaxy.
So one possible explanation is that there must be other galaxies,
probably fainter and less massive neighbours,
that helped ionise the hydrogen in the region of space around the galaxy,
thus making it transparent.
Without this additional help
the brilliant light from the main galaxy
would have been trapped in the surrounding hydrogen fog
and it could not have even started its 13-billion-year journey towards Earth.
Studying the era of reionisation
and the formation of the first galaxies
is really pushing the capabilities
of current telescopes and instruments to the limit.
But, this will be exactly the type of science
that ESO’s European Extremely Large Telescope will excel at.
Once operational,
this will be the largest optical and infrared telescope in the world.
This is Dr J signing off for the ESOcast.
Join me again next time for another cosmic adventure.
ESOcast is produced by ESO, the European Southern Observatory.
ESO, the European Southern Observatory, is the pre-eminent intergovernmental science and technology organisation in astronomy
designing, constructing and operating the world’s most advanced ground-based telescopes.
Transcription by ESO ; translation by —
Now that you've caught up with ESO,
head 'out of this world' with Hubble.
The Hubblecast highlights the latest discoveries
of the world's most recognized and prized space observatory,
the NASA/ESA Hubble Space Telescope