M89: Elliptical Galaxy with Outer Shells and Plumes
| APOD
Image Credit & Copyright: Mark Hanson
Can you see them? This famous Messier object M89, a seemingly simple elliptical galaxy, is surrounded by faint shells and plumes. The cause of the shells is currently unknown, but possibly
tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where a recent collision with another large galaxy created density
waves that ripple through this galactic giant. Regardless of the actual cause, the
featured image
highlights the increasing consensus that at least some elliptical
galaxies
have formed in the recent past, and that the outer halos of most
large galaxies are not really smooth
but have complexities induced by frequent interactions with – and accretions of –
smaller nearby galaxies. The halo of our own
Milky Way Galaxy
is one example of such
unexpected complexity. M89 is a member of the nearby Virgo cluster of galaxies which lies about 50 million light years distant.
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