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3.2 billion light years from Earth,

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a group of astronomers
has captured live with Hubble

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something they never thought
they would get to see.

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This is the Hubblecast.

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News and images from the
NASA / ESA Hubble Space Telescope.

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Travelling through time and space
with our host, Dr. J

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EPISODE 1: The Comet Galaxy

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There are many galaxies
of different shapes and sizes

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in the universe around us today.

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Roughly half are gas poor,
elliptical shaped galaxies

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with few new stars forming today.

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Whereas the other half are gas rich,
spiral and irregular shaped galaxies

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with lots of new star
formation activity.

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Now, observations have shown
that the gas poor galaxies

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are often found near the centers
of rich galaxy clusters,

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whereas the spirals spend
most of their life in solitude.

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However, observations of the deep
and very far away universe

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have also shown that when universe
was roughly half of its present age

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things were very different.
Back then, only about 1 in 10 galaxies

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was a gas poor one.
So the question is:

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where did all today's gas poor
galaxies come from?

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Apparently, there must has been
some kind of transformation process.

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But because galaxy evolution
takes place over billions of years

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astronomers have so far
not been able to see it live.

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New observations with Hubble
by an international team

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led by Luca Cortese of
Cardiff University, United Kingdom,

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provide one of the best examples today
to this metamorphosis.

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Well, we were looking at the
Abell Cluster 2667

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and we realized that this galaxy
was falling into the cluster center

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at a velocity of approximately
2.5 million kilometers per hour.

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Abell 2667's enormous
gravitational field

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is generated
by the combined contribution

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of the cluster's dark matter, hot gas
and hundreds of galaxies.

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As the galaxy
plunges through the cluster

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its gas and stars
are been stripped away

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by the hot plasma in the cluster,
which can reach temperatures

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as high as 10 to 100 million degrees.

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Also contributing
to this destructive process

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are the tidal forces
exerted by the cluster.

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This are just like the tidal forces
of the Moon and Sun,

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which push and pull
the Earth's oceans.

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Birth processes,
the tidal forces

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and the aptly named
"ram pressure stripping"

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resulting from the action
of the hot cluster gas

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resemble those affecting comets
in our Solar System.

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For this reason, scientists have
nicknamed this peculiar spiral

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 with its tail, the "Comet Galaxy".

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We see a unique galaxy that
has been transformed by the fact

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it's falling towards the cluster center.

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And what it is exactly, it's a kind
of a spiral galaxy with lots of gas.

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And we see a trail of stars,
of blue forming stars.

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And also around those stars
some kind of wispy gas

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stripped away by the fall.

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Furthermore, millions of now homeless
stars have been snatched away

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from their mother galaxy, which
will lead it to age prematurely.

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Even though its mass is slightly
larger than that of the Milky Way,

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the spiral will inevitably lose all
its gas and dust and hence

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his chance of generating new
stars later. So, it'll probably become

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a gas poor galaxy left with an
old population of red stars.

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However, in the midst
of all this destruction,

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the cluster strong tidal forces

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have triggered a baby-boom
of star formation.

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Hubble's sharp eyes have caught
other spectacular effects

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of Abell 2667's immense mass.

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The giant bluish arc
seen just off-center

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is the magnified and distorted image
of a distant background galaxy

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seen through the gravitational lens
formed by the tremendous

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mass concentration
of the cluster.

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At the cluster's center,
another rare feature can be seen:

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the vivid blue light
from millions of stars

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created in a so called
cooling flow.

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Some of the hot cluster gas
is cooling in a filamentary structure

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as it falls into the cluster's core,
setting off the birth

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of lots of bright blue stars
outshining their environment.

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This may be the clearest picture
of this phenomenon yet.

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By combining the visible, infrared
and x-rays views

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from Hubble, Spitzer, Chandra,
the VLT and Keck

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we can see that this discovery
adds a new brush-stroke

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to a painting were galaxies
are being slowly shaped

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by their violent interactions
with the cluster environment.

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Although there are many
discoveries still to come

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the emerging elements shed new light
on the painting's mysterious nature

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and are revealing some
of its hidden wonders.

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This is Dr. J
signing off for the Hubblecast

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Once again, nature has surprised us
beyond our wildest imagination...

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Hubblecast is produced
by ESA / Hubble

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at the European
Southern Observatory in Germany.

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The Hubble mission is a project
of international cooperation

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between NASA and
the European Space Agency.