The Cartwheel, interacting galaxies in Sculptor
Tags: galaxy, spiral
This diminutive group of galaxies appears small because it is
distant, about 500 million light years away. But here, a dramatic
collision between two members of a small group has transformed
one of them into a brilliant ring of stars, connected to the
bright nucleus by starry tendrils that are reminiscent of the
spokes of a wheel.
The Cartwheel itself was a galaxy about as
big as the Milky Way probably with much the same spiral
structure. However, one of the small companion galaxies has
recently passed through its center. This is perfectly possible — the stars are so far apart that collisions are rare. But the
intruder intercepted the galaxy almost at right angles to the
disk and it passed through the gravitational hub of the galaxy,
the bright nucleus. The gravitational pulse of the interaction
sent a ripple of energy through the galaxy disk, triggering a
violent wave of star formation which has spread as far as the
visible outer rim. The youth of this feature is evident from its
color, which is the pale blue of young stars.
Made from "Tek 1" CCD UVB data obtained by Steve Lee and David Malin in September 1997
Top left is NE. Image width is about 7 arc min.
© Australian Astronomical Observatory