Galaxies essentially have three different shapes. The vast majority are flattened discs, often with spiral arms; some are ellipsoids, like rugby balls; and a few are completely irregular with no symmetry.
So the discovery of a galaxy with an entirely different shape is bound to generate a flutter of interest.
Today, Alister Graham at Swinburne University of Technology in Australia and a few mates announce the discovery of a dwarf galaxy designated LEDA 074886 that is distinctly rectangular. “We affectionately call [it] the “emerald cut galaxy” given its striking resemblance to an emerald cut diamond,” they say.
The galaxy sits in a group of about 250 dwarf galaxies some 21 megaparsecs from Earth in the constellation of Eridanus. It’s just a nipper, with a mass some 10 billion times that of the Sun. By contrast, the Milky Way is about a thousand times heavier.
The obvious question is how did it form. Graham and co think the emerald cut galaxy formed from the merger of two disc galaxies, like a couple of pancakes on top of each other. From the side, this looks rectangular.
That’s clearly a rare type of event but not entirely unknown. Graham and co say astronomers have discovered seven other rectangular examples out of the many millions of galaxies they’ve catalogued.
However, we may not have to look far to find another exotic shape. A couple of years ago, astronomers said they’d found evidence that the arms of the Milky Way were straightish, giving our galaxy a distinctly square look, like the Pinwheel galaxy, M101.
Ref: arxiv.org/abs/1203.3608: LEDA 074886: A Remarkable Rectangular-Looking Galaxy