Because they are so far away and light has taken so long to travel from them, we see distant galaxies as they were billions of years ago. Studying the early stages of these galaxies — such as those that formed just 2 billion–3 billion years after the Big Bang — can help us to understand how galaxies evolve into present-day systems such as our Milky Way. So far, most work has focused on information assembled from many galaxies that sheds light on important aspects of development, such as star formation rates. But, to amass more details of galaxy formation through time, scientists need knowledge of individual galaxies' internal structures — for example, the motion of gases within them.

During the next decade, high-powered telescopes will help to realize that goal. In the meantime, the application of technological advances to existing telescopes has allowed astronomers to amplify the light behind massive galaxy clusters to effectively create a zoom lens. This technique is known as gravitational lensing.

Daniel Stark, a postdoc at the California Institute of Technology (Caltech) in Pasadena, teamed up with colleagues at Caltech and in the United Kingdom to use gravitational lensing to zoom in on a distant galaxy. The group also took advantage of two other innovations: first, integral field spectrography, which can be used to provide spectra from many locations across a galaxy to give two-dimensional measurements of velocity; second, laser-guided adaptive optics, which correct for the blurring of the atmosphere, and allowed the team to more clearly determine whether a distant galaxy is rotating.

Perhaps most importantly, the researchers needed the perfect galaxy to study — one that was both distant and bright enough. In 2006, co-author Ian Smail of Durham University, UK, and his collaborators had discovered a galaxy referred to as the Cosmic Eye using gravitational lensing. One month later, Stark's Caltech co-authors Richard Ellis and Johan Richard confirmed that it formed just 2 billion years after the Big Bang.

In July 2007, Stark and co-author Mark Swinbank, a Durham University postdoc, had booked one night on Hawaii's Keck telescope to measure the galaxy's internal structure. Unfortunately, Stark's flight was cancelled, but the observations proved fruitless anyway because of clouds — a common frustration for astronomers. Two months later, Stark made it to Hawaii with Ellis, Swinbank and Richard, and they succeeded in measuring the movement of ionized gas within the galaxy. Swinbank conducted the preliminary analyses in real time at the telescope. “By the end of the night, we had preliminary evidence for rotation in this distant galaxy, which was very exciting because it provided the most detailed view yet achieved of a young galaxy in the early Universe,” Stark says.

Stark then compared the galaxy's known distribution of molecular gases with that of ionized gas measured at Keck. He confirmed that the cold molecular gas — which was being converted into stars — shared the same rotation pattern as the ionized gas (see page 775). These measurements will help to determine at what point in their lifetimes galaxies acquire angular momentum and how galaxies grow over time. For example, the findings may help to resolve the relative importance of galaxy collision versus gas accumulation in galaxy assembly, Stark says.

As a young scientist, Stark can see one other thing clearly in these data — a life's worth of work ahead. “It is exciting to get a glimpse of what I and others will be able to do once future facilities, such as the Thirty Meter Telescope and the Atacama Large Millimeter Array, allow us to easily sample more distant galaxies,” he says.