Horsehead Nebula. Zooming to a Hubble Space Telescope (HST) view of the Horsehead Nebula (Barnard 33). This nebula lies around 1600 light years from Earth in the constellation of Orion. The horsehead shape, several light years across, is formed by an intrusion of dust into the emission nebula IC 434. The red glow from this nebula is due to the ionisation of hydrogen by radiation from nearby stars. Composite created using data from Hubble's Wide Field Camera 3, and the European Southern Observatory's Visible and Infrared Survey Telescope for Astronomy (VISTA).