An artist's rendition of the ancient BX442. (Photo : Joe Bergeron)
Using the Hubble Space Telescope, astronomers peering back into the very depths of time and space have found the oldest spiral galaxy ever discovered. The galaxy, dated to around 10.7 billion years ago, existed billions of years before other known spiral galaxies formed.
Named, BX442, the ancient spiral galaxy is an oddity. Most incredibly old galaxies are random clumps and irregular-shaped. BX442, on the other hand, has the spiral beauty of our own galaxy.
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"The fact that this galaxy exists is astounding," said David Law, lead author of the study and Dunlap Institute postdoctoral fellow at the University of Toronto's Dunlap Institute for Astronomy & Astrophysics. "Current wisdom holds that such 'grand-design' spiral galaxies simply didn't exist at such an early time in the history of the universe."
These 'grand design' galaxies mean that it has full, well-formed spiral arms. Spiral galaxies tend to have stars that rotate together and are where new stars are formed. Another type of galaxy, an elliptical galaxy, usually contains older, redder stars that are moving about random.
The age of the galaxy means that the light from that galaxy has taken 10.7 billion years to reach, allowing us to view the universe just 3 billion years after it was formed.
The galaxy could provide insight into the formation of galaxies and how the universe is structured today.
"BX442 looks like a nearby galaxy, but in the early universe, galaxies were colliding together much more frequently," said co-author Charlotte Christensen. "Gas was raining in from the intergalactic medium and feeding stars that were being formed at a much more rapid rate than they are today; black holes grew at a much more rapid rate as well. The universe today is boring compared to this early time."
"Indeed, this galaxy may highlight the importance of merger interactions at any cosmic epoch in creating grand design spiral structure," said co-author Alice Shapely.