Explanation:
Scanning the skies for galaxies, Canadian astronomer
Paul Hickson and colleagues identified some 100 compact
groups
of galaxies, now appropriately called
Hickson Compact Groups.
The four prominent galaxies seen in this intriguing
telescopic skyscape
are one such group, Hickson 44, about 100 million
light-years distant toward the constellation Leo.
The two spiral galaxies
in the center of the image are edge-on NGC 3190 with its distinctive,
warped dust lanes, and S-shaped NGC 3187.
Along with the bright elliptical, NGC 3193 at the right,
they are also known as Arp 316.
The spiral in the upper left corner is NGC 3185,
the 4th member of the Hickson group.
Like other galaxies in Hickson groups, these show signs of
distortion and enhanced star formation,
evidence of a gravitational tug of war that will eventually result in
galaxy mergers on a cosmic timescale.
The merger process is
now understood to be a normal part of the evolution of
galaxies, including
our own Milky
Way.
For scale, NGC 3190
is about 75,000 light-years across at the estimated
distance of Hickson 44.
APOD Retrospective:
Small Groups of Galaxies
