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A recent NASA / ESA Hubble
Space Telescope image

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captures what appears to be one
very bright and bizarre galaxy

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but is actually the result of a pair of
spiral galaxies, like our own Milky Way,

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smashing together at incredible speeds.

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This object was a target of Hubble's
and a handful of its "sibling" spacecraft

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as part of a massive comprehensive
sky survey called GOALS.

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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 31: Sky mergers yields
sparkling dividends
a.k.a. Dr. Joe Liske.

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Hi and welcome to the Hubblecast.

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This new image of NGC 2623, which is
located in the constellation of Cancer,

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was taken by Hubble's Advanced
Camera for Surveys, or ACS,

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before the recent
Hubble servicing mission.

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Once two distinct galaxies, NGC
2623 is a nearly complete merger,

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with elements of both original galaxies
affecting its appearance and behaviour.

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Colliding galaxies engage in a
powerful exchange of material,

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they literally throw matter and gas
toward one another as they race together.

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Stretching out from the center of NGC
2623, are two tidal tails of young stars

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showing that a merger has taken place.

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The dramatic exchange of mass and gases

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initiate star formation
seen there in both the tails.

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The prominent lower tail is richly
populated with bright star clusters.

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These star clusters may have formed
as part of a loop of stretched material

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associated with the northern tail,

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or they may have formed from debris
falling back onto the nucleus.

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In addition to this
active star-forming region,

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both galactic arms
harbour very young stars

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in the early stages of
their evolutionary journey.

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The core or nucleus of this merged
galaxy is exceedingly bright.

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Often this mergers, including this case,
result in an active galactic nucleus,

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where one of the
super-massive black holes

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found at the center of
the two original galaxies

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is stirred into action.

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Matter is pulled toward the black
hole forming an accretion disc.

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The energy released by the
frenzied motion heats up the disc

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causing it to emit across a wide
range of the electromagnetic spectrum.

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Although rare in our
solar neck of the woods,

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extremely bright galaxies like NGC 2623

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exist at higher redshifts
or, in other words,

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at an early stage of the Universe's
evolution when these systems were dominant.

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Their brightness
signals furious activity,

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new star formation and
a rambunctious core.

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The aim of the GOALS project is to use the
combined powers of multiple space telescopes

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to characterise their local counterparts
and give us clues as to what is happening

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in more distant galaxies while
educating us about galaxy formation.

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Each telescope in the GOALS
project brings different strengths.

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Hubble's incredible
resolution in the visible

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allows us to scrutinise the
galaxy's morphology, or structure.

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In these images, astronomers can
determine the stage of the merger.

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For example, has the
union produced tidal tails?

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Have the individual galaxies'
cores melted together as one?

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Chandra's X-ray capabilities allow the
astronomers to detect the flurry of activity

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around the black holes and
to monitor new star formation.

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Spitzer contributes in the infrared,

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penetrating dust, allowing astronomers to
see what lurks behind the eerie dust lanes.

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GALEX is powerful in the ultraviolet,
gathering the light of developing stars.

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Data from ESA's X-ray Multi-Mirror
Telescope, or XMM-Newton,

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also helped astronomers gain
more information about NGC 2623.

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The joint efforts of these
powerful observing facilities

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has provided a clearer picture
of these standout galaxies.

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Galaxy evolution is a
hot topic in astronomy

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because it is fundamental to our
understanding of the Universe.

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Studying merging
galaxies such as NGC 2623,

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allows astronomers to witness the
shaping of new, combined galaxies

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and the subsequent birth of stars.

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This could even provide essential
information about our own Milky Way,

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that has cannibalised other
small galaxies and could, one day,

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collide with our neighbour,
the Andromeda Galaxy.

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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.

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Now that you've caught up with Hubble

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make sure to get the
latest from the ground too.

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The ESOCast highlights the best of
the European Southern Observatory

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and its powerful telescopes that
observe from high in the Chilean Andes

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at the southern hemisphere's best known
sites for astronomical observations.