Solar filament. Time-lapse Solar Dynamics Observatory (SDO) ultraviolet footage of a long solar filament (lower left and moving to lower centre) reaching for hundreds of thousands of kilometres across the Sun. Filaments are elongated clouds of cooler gases, tethered above the solar surface by powerful magnetic forces. They are often unstable and prone to erupting. The SDO is an Earth-orbiting spacecraft launched in 2010 by NASA and used to observe the Sun. Here, the Sun is seen at a wavelength of 304 angstroms (extreme ultraviolet). This channel shows areas where cooler, dense plumes of plasma (such as filaments and prominences) occur above the visible surface of the Sun, and are seen in the upper chromosphere and lower transition region. This footage was obtained during the period 19-23 January 2014.