Our View of Galaxies Keeps Changing

by Alan Eggleston

Much of what we thought we knew about galaxies has changed over the past few years.

Photo: Hubble Image of M100 Spiral Galaxy (NASA).  Released to public.

Photo: Hubble Image of M100 Spiral Galaxy (NASA). Released to public.

Not long ago, a citizen science project launched called Zooniverse, which challenged everyday amateur astronomers to help scientists to classify galaxies as either spirals or ellipticals. Then it became, do spirals spin clockwise or counterclockwise? Galaxy classifications have been more complex than that for decades, but this was the beginning of a more thorough review of images to actually look at the universe of galaxies and classify them. It’s gone far beyond that now. The project even found some surprises like “peas” and began exploring early gas clouds as they clumped into galaxies. They broadened the project to explore galaxy mergers and then looked more closely at our home galaxy, the Milky Way. Throughout the effort – and beyond it as other scientists did their own work – the consensus on galaxies was that they are more complex and different than we ever imagined.

Just recently, astronomers discovered a supermassive black hole in a dwarf galaxy. A question has been, which came first – the supermassive black hole or the galaxy of stars that surround one? A first guess suggested that supermassive black holes give rise to galaxies, since every galaxy seems to have one. But this new discovery might make you think otherwise – this newly discovered supermassive black hole is the size of 21 million Sols! (The supermassive black hole at the center of the Milky Way is a comparatively small 4 million Sols.)

Not all that long ago, it was presumed that elliptical galaxies were formed out of old, merged spiral galaxies. Now astronomers aren’t so sure that’s true. Studies of mergers show, merged spirals may actually form more disc-shaped galaxies, including spirals – so how do elliptical galaxies form? Intriguing question!

Equally intriguing, scientists have extended the reach of our vision into the size and scope of our galactic neighborhood. We knew the Milky Way was part of a supercluster of galaxies, but now we have found that we are at the very end (a cul-de-sac?) of a newly discovered supergalactic supercluster.

As our telescopic instruments become more refined and more sophisticated, we’ve been able to peer ever further into the distance. The farthest viewed galaxy is now 13.7 billion light years away. That’s nearly at the edge of the universe. The farther we look, the earlier in galactic formation we are able to see. Yet the wider we look, the more variety and range we see. It’s an exciting time of discovery in every corner of astronomy and cosmology.


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