To mark UNESCO's International Year of Astronomy (IYA2009), six leading astronomers from the UK, the US, Europe and Asia write in March's Physics World about the biggest challenges and opportunities facing international astronomers over the next couple of decades.
Many of those challenges are purely scientific, including the quest to clarify the true nature of dark matter and dark energy; the search for extra-terrestrial life among the myriad of extrasolar planets that are set to be discovered; and finding the first stars that formed after the Big Bang.