Over the last 25 years,
the NASA/ESA Hubble Space Telescope has revealed the distant Universe with ever-increasing depth
through the Deep and Ultra Deep fields.
Hubble has embarked on an ambitious new programme
to push even further towards the Universe’s furthest frontiers.
Hello, and welcome to another episode of the Hubblecast!
In 2013, Hubble began a campaign
to capture very deep images
of some of the most massive structures in the Universe
— galaxy clusters.
The Frontier Fields campaign
is using six of these giants
to peer into the farthest reaches of the Universe.
The enormous amount of mass in a galaxy cluster means
that it bends the space around it
and acts like a gigantic magnifying glass.
This process is known as gravitational lensing
and it allows astronomers to study objects behind the cluster
in the very distant Universe
that would normally be too faint to see
even for Hubble.
Abell 2744.
One of the first and most captivating targets of the Frontier Fields campaign.
Like all large galaxy clusters,
Abell 2744’s mammoth mass is warping the space around it
and magnifying the light from distant galaxies behind it.
This produces weird and wonderful arrangements of warped light
in the form of arcs and distorted shapes.
Magnified by Abell 2744,
some of the most distant galaxies ever found became visible.
These galaxies are so distant
that the light Hubble has captured from them
was emitted when the Universe was just 500 million years old.
These distant galaxies
— some of the first to form in the Universe —
offer astronomers a glimpse of the conditions in the early Universe.
One of the most distant clusters studied
is MACS J1149.5+2223
— so distant that it takes the light five billion years to reach us!
Using this cluster
Hubble has captured a rare event for the first time:
the gravitationally lensed image of a supernova,
arranged four times in a galaxy in the cluster.
The light from the dying star
was magnified by the mass of the cluster.
And as it is perfectly aligned with one of the galaxies in the cluster,
its light has been split into four images.
By studying gravitational lensing,
astronomers are able to map out the total amount of matter in galaxy clusters.
Now, this mapping is a very valuable tool
in the search for one of the most elusive components of the Universe
— dark matter.
If the galaxy cluster
contained only the matter that we can see directly,
it would never have the gravitational power to distort the light as we observe it.
So there must be additional dark matter present,
and gravitational lensing tells us how this dark matter is distributed
within the cluster.
In the case of MACSJ1149,
our understanding of the distribution of dark matter is in fact so good
that it allowed us to predict the appearance of a fifth image of the lensed supernova
in December 2015,
and, lo and behold,
this appearance has in fact been observed as predicted.
As well as observing the clusters,
Hubble puts its multiple cameras to use during the cluster observations
by also observing six parallel fields
— regions near the galaxy clusters.
While these adjacent images cannot be used for gravitational lensing,
Hubble uses them to perform deep-field observations
and therefore to give astronomers
an even larger window on the early Universe.
So far,
Hubble has completed the observations for three of the six Frontier Fields clusters
and their parallel fields.
These data are already teaching us a lot about the very early Universe
and they are paving the way for the James Webb Space Telescope
in its quest for the very first generation of galaxies.
This is Dr J, signing off for the Hubblecast.
Once again,
nature has surprised us
beyond our wildest imagination.
Transcription by ESO; translated by —