In March of 2012, an international
team of astronomers discovered a rectangular‑shaped galaxy within a
group of 250 galaxies some 70 million light years away. “In the Universe around us,
most galaxies exist in one of three forms: spheroidal, disc-like, or
lumpy and irregular in appearance,” said Alister Graham from Swinburne University of Technology.
The rare rectangular-shaped galaxy was a very unusual object. “It's one
of those things that just makes you smile because it shouldn't exist,
or rather you don't expect it to exist. It’s a little like the
precarious Leaning Tower of Pisa or the discovery of some exotic new species which at first glance appears to defy the laws of nature.”
The unusually shaped galaxy was detected in a wide field-of-view image taken with the Japanese Subaru Telescope
for an unrelated program by Swinburne astrophysicist Dr Lee Spitler.The
astronomers suspect it is unlikely that this galaxy is shaped like a
cube. Instead, they believe that it may resemble an inflated disc seen
side on, like a short cylinder.
Support for this scenario comes from observations with the giant Keck Telescope
in Hawaii, which revealed a rapidly spinning, thin disc with a side‑on
orientation lurking at the centre of the galaxy. The outermost measured
edge of this galactic disc is rotating at a speed in excess of 100,000 kilometres per hour.
“One possibility is that the galaxy may have formed out of the
collision of two spiral galaxies,” said Swinburne’s Professor Duncan
Forbes, co‑author of the research. “While the pre-existing stars from
the initial galaxies were strewn to large orbits creating the emerald
cut shape, the gas sank to the mid‑plane where it condensed to form new
stars and the disc that we have observed.”
Despite its apparent uniqueness, partly due to its chance
orientation, the astronomers have managed to glean useful information
for modelling other galaxies.While the outer boxy shape is somewhat
reminiscent of galaxy merger simulations which don’t involve the
production of new stars, the disc-like structure is comparable with
merger simulations involving star formation.
“This highlights the importance of combining lessons learned from
both types of past simulation for better understanding galaxy evolution
in the future,” said Associate Professor Graham.“One of the reasons this
emerald cut galaxy was hard to find is due to its dwarf-like status: it
has 50 times less stars than our own Milky Way galaxy,
plus its distance from us is equivalent to that spanned by 700 Milky
Way galaxies placed end-to-end.“Curiously, if the orientation was just
right, when our own disc-shaped galaxy collides with the disc-shaped Andromeda galaxy about three billion years from now we may find ourselves the inhabitants of a square looking galaxy.”
The results will be published in The Astrophysical Journal.
Source: The Daily Galaxy via Swinburne University of Technology
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