Astronomy Picture of the Day

Explanation: Three dark dust lanes give the picturesque Trifid Nebula its name. The red and blue colours of the Trifid Nebula are present in different regions and are created by different processes. A big bright star near the centre of the red region appears white hot and emits light so energetic it knocks electrons away from gas surrounding it. When an electron is recaptured by a proton, red light is frequently emitted. The blue region is centred on another bright star but this region's dust reflects light to us. The two regions are thus called an emission nebula and reflection nebula, respectively. The Trifid Nebula can be seen in Sagittarius toward the Galactic Centre with a small telescope.