Active galaxy. Hubble Space Telescope (HST) ultra- violet spectrograph image of the active (Seyfert) galaxy NGC 4151, thought to contain a black hole. The image shows carbon IV emission at a wavelength of 1549 angstroms (154.9 nanometres). Gas emitting light at this wavelength is extremely energetic, meaning it is close to the energy source powering the galaxy (its super-massive black hole). The emitting gas is found in knots which are being ejected from the galaxy's nucleus at high speeds. This ejection occurs in two beams (not seen), one carrying gas towards us and one away from us.