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3.2 billion light years from Earth,
a group of astronomers has captured live with Hubble
something they never thought they would get to see.
This is the Hubblecast.
News and images from the NASA / ESA Hubble Space Telescope.
Travelling through time and space with our host, Dr. J
EPISODE 1: The Comet Galaxy
There are many galaxies of different shapes and sizes
in the universe around us today.
Roughly half are gas poor, elliptical shaped galaxies
with few new stars forming today.
Whereas the other half are gas rich, spiral and irregular shaped galaxies
with lots of new star formation activity.
Now, observations have shown that the gas poor galaxies
are often found near the centers of rich galaxy clusters,
whereas the spirals spend most of their life in solitude.
However, observations of the deep and very far away universe
have also shown that when universe was roughly half of its present age
things were very different. Back then, only about 1 in 10 galaxies
was a gas poor one. So the question is:
where did all today's gas poor galaxies come from?
Apparently, there must has been some kind of transformation process.
But because galaxy evolution takes place over billions of years
astronomers have so far not been able to see it live.
New observations with Hubble by an international team
led by Luca Cortese of Cardiff University, United Kingdom,
provide one of the best examples today to this metamorphosis.
Well, we were looking at the Abell Cluster 2667
and we realized that this galaxy was falling into the cluster center
at a velocity of approximately 2.5 million kilometers per hour.
Abell 2667's enormous gravitational field
is generated by the combined contribution
of the cluster's dark matter, hot gas and hundreds of galaxies.
As the galaxy plunges through the cluster
its gas and stars are been stripped away
by the hot plasma in the cluster, which can reach temperatures
as high as 10 to 100 million degrees.
Also contributing to this destructive process
are the tidal forces exerted by the cluster.
This are just like the tidal forces of the Moon and Sun,
which push and pull the Earth's oceans.
Birth processes, the tidal forces
and the aptly named "ram pressure stripping"
resulting from the action of the hot cluster gas
resemble those affecting comets in our Solar System.
For this reason, scientists have nicknamed this peculiar spiral
with its tail, the "Comet Galaxy".
We see a unique galaxy that has been transformed by the fact
it's falling towards the cluster center.
And what it is exactly, it's a kind of a spiral galaxy with lots of gas.
And we see a trail of stars, of blue forming stars.
And also around those stars some kind of wispy gas
stripped away by the fall.
Furthermore, millions of now homeless stars have been snatched away
from their mother galaxy, which will lead it to age prematurely.
Even though its mass is slightly larger than that of the Milky Way,
the spiral will inevitably lose all its gas and dust and hence
his chance of generating new stars later. So, it'll probably become
a gas poor galaxy left with an old population of red stars.
However, in the midst of all this destruction,
the cluster strong tidal forces
have triggered a baby-boom of star formation.
Hubble's sharp eyes have caught other spectacular effects
of Abell 2667's immense mass.
The giant bluish arc seen just off-center
is the magnified and distorted image of a distant background galaxy
seen through the gravitational lens formed by the tremendous
mass concentration of the cluster.
At the cluster's center, another rare feature can be seen:
the vivid blue light from millions of stars
created in a so called cooling flow.
Some of the hot cluster gas is cooling in a filamentary structure
as it falls into the cluster's core, setting off the birth
of lots of bright blue stars outshining their environment.
This may be the clearest picture of this phenomenon yet.
By combining the visible, infrared and x-rays views
from Hubble, Spitzer, Chandra, the VLT and Keck
we can see that this discovery adds a new brush-stroke
to a painting were galaxies are being slowly shaped
by their violent interactions with the cluster environment.
Although there are many discoveries still to come
the emerging elements shed new light on the painting's mysterious nature
and are revealing some of its hidden wonders.
This is Dr. J signing off for the Hubblecast
Once again, nature has surprised us beyond our wildest imagination...
Hubblecast is produced by ESA / Hubble
at the European Southern Observatory in Germany.
The Hubble mission is a project of international cooperation
between NASA and the European Space Agency.