These two images of the spectacular merger of the nearby Antennae galaxies — on the left from NASA's Spitzer Space Telescope, on the right from the Hubble Space Telescope — show the train wreck of two gas-rich spirals. The proximity of the galaxies allows detailed imaging of newborn star clusters and the infrared hotspots that mark starburst sites. The dusty regions between the two galaxies, heavily obscured in the Hubble optical image, are in fact the dominant sites of active star formation as traced by the Spitzer Infrared Array Camera at an infrared wavelength of 8 micrometre emission (red). Indeed, the brightest infrared hotspot (centre left of the Spitzer image) is almost entirely unseen. Extreme starbursts near and far are more than several tens of times brighter than the Antennae galaxies, and the most intense examples are usually hidden in dust, making comparisons between observations at different redshifts particularly tricky.