Astronomers using the Hubble Space Telescope have have witnessed the earliest spiral galaxy ever seen. The spiral galaxy BX442 formed in the early universe, billions of years before many other spiral galaxies formed. The early universe was thought to be far too chaotic for the formation of a symmetrical spiral galaxy. An artist's rendering of galaxy BX442 and its companion dwarf galaxy (upper left) is pictured above.
In findings reported here
in the journal Nature
, the astronomers said they discovered BX442 while using Hubble to take pictures of about 300 very distant galaxies in the early universe so they could study their properties. This distant spiral galaxy is being observed as it existed roughly three billion years after the Big Bang. Light from this part of the universe has been traveling to Earth for about 10.7 billion years.
Alice Shapley, a UCLA associate professor of physics and astronomy, and co-author of the study, says, "As you go back in time to the early universe, galaxies look really strange, clumpy and irregular, not symmetric. The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?"
David Law, lead author of the study and Dunlap Institute postdoctoral fellow at the University of Toronto's Dunlap Institute for Astronomy & Astrophysics, says, "The fact that this galaxy exists is astounding. Current wisdom holds that such 'grand-design' spiral galaxies simply didn't exist at such an early time in the history of the universe."
The galaxy is also quite large compared with other galaxies from this early time in the universe. Only about 30 of the galaxies that Law and Shapley analyzed are as massive as this galaxy. Law and Shapley also say they found some evidence of an enormous black hole at the center of the galaxy. The astronomers examined 3,600 locations in and around BX442 using the OSIRIS spectrograph
at the W.M. Keck Observatory to make sure this was a true galaxy and not an illusion, such as two galaxies that happened to line up to form the image.
Shapley says, "We first thought this could just be an illusion, and that perhaps we were being led astray by the picture. What we found when we took the spectral image of this galaxy is that the spiral arms do belong to this galaxy. It wasn't an illusion. We were blown away."
Image: Dunlap Institute for Astronomy & Astrophysics/Joe Bergeron