When James Hinton was working at the Enrico Fermi Institute in Chicago, he heard about plans to build a telescope system that would measure high-energy cosmic rays. So he packed his bags and joined the Max-Planck-Institute for Nuclear Physics in Heidelberg to be part of an international collaboration involving 100 astrophysicists from eight different countries. “It turned out to be a good move,” says the Leeds University graduate and lead author of a study published on page 695 of this issue of Nature.

The paper, the latest in a series from the High Energy Stereoscopic System (HESS) team, describes evidence of a burst of acceleration of cosmic rays that occurred 10,000 years ago in the Milky Way. Such Galactic rays are thought to originate in the shock waves from supernova explosions. The team gathered the data with an array of four Cherenkov telescopes at Windhoek, Namibia, which was built with money and manpower from Germany, France, Namibia, the UK, the Republic of Ireland, the Czech Republic, Armenia and the Republic of South Africa. The area in Namibia is well known for its excellent conditions for optical astronomy.

Now, the same scientists involved in the design and construction of the telescope system are reaping the fruits of their labours. But doing so requires much coordination and communication among disparate research groups. Every year, members of HESS put together proposals for different observation targets, reviewed by one of seven physics groups of different areas of expertise. Then the groups make recommendations to an observation committee to decide how many hours of data collection to devote to each approved research project.

Data are gathered in Namibia by a monthly shift crew of two or three people, assisted by a local team. The data are simultaneously sent to Lyon and Heidelberg, from where they are distributed to scientists at participating universities and institutes. “When the data comes in we grab hold of it and perform some quick analyses. Some people are more interested in a specific angle,” says Hinton. “You then discuss with the group what you want to write up.” For any particular study, two separate groups conduct parallel analyses and check the other's work, allowing all members input on this paper,” explains Hinton. “The process can be complicated when writing a paper because everyone has strong opinions about what the data mean,” he adds.

Although a number of telescopes can measure high-energy cosmic rays, none comes close to the level of precision of HESS. This means that scientists can home in on the exact location of the rays in an attempt to deduce their source. One of the first targets of analysis by the HESS team has been the centre of the Milky Way, which harbours a number of potential gamma-ray sources, including a supermassive black hole, remnants of supernova explosions and dark-matter particles.

Discussions for the next-generation telescope system kicked off in 1995, but construction did not begin until 2001 and was completed in 2004. The project is now heading into a second phase in which an even larger (28 metres in diameter) telescope will be added to the research set-up.