Astronomers have found a spiral galaxy that formed much earlier than astronomers thought possible, a find that could lead to insights into how galaxies like our Milky Way evolved from more chaotic and disc-like structures into grand spirals.
In the journal Nature, a team led by University of Toronto researcher David Law described Wednesday how they examined this galaxy, dubbed BX442, from an observatory on top of Hawaii's dormant Mauna Kea volcano. The astronomers' observations are a snapshot of the galaxy's distant past, since the light has been traveling to Earth for nearly 11 billion years.
What they saw was a galaxy much larger than most others that existed at that time in the universe (about 3 billion years after the Big Bang). BX442's spiral shape also made it stand out from the rest.
As you go back in time to the early universe, galaxies look really strange, clumpy and irregular, not symmetric, co-author and UCLA professor Alice Shapley said in a statement Wednesday. The vast majority of old galaxies look like train wrecks. Our first thought was, why is this one so different, and so beautiful?
The authors think that BX442 may have been twisted into a spiral thanks to gravitational interactions with a nearby dwarf galaxy.
Boston University astronomer Alan Marscher, who was unaffiliated with the current study, said that conclusion is reasonable.
Other scientists have performed numerical experiments on computers showing that interactions via gravity of two galaxies can cause a galaxy to organize into a spiral pattern, Marscher said in an email.
July has been a banner month for space enthusiasts.
Just last week, the European Southern Observatory announced that researchers had used its Very Large Telescope in Chile to catch the first possible glimpse of a dark galaxy, which are devoid of stars but rich in gas. Dark galaxies have long been thought to be the building blocks of the star-laden structures we're familiar with, but until now, they have not been directly observed.
But how do you see something that gives off no light?
Our approach to the problem of detecting a dark galaxy was simply to shine a bright light on it, co-author Simon Lilly explained in a statement on July 12.
The researchers looked for signs of a fluorescent glow from dark galaxies caused by ultraviolet light given off by nearby quasars -- the nuclei of other galaxies.
The light from the quasar makes the dark galaxies light up in a process similar to how white clothes are illuminated by ultraviolet lamps in a night club, Lilly said.
SOURCE: Law et al. High velocity dispersion in a rare grand-design spiral galaxy at redshift z=2.18. Nature 487: 338-340, 19 July 2012.