Sharpless 264, also known as the Lambda Orionis Ring, is a molecular cloud and H II region, which can be seen in the northern region of the Orion Molecular Cloud Complex (OMCC), in the constellation of Orion. The OMCC is one of the best-known star formation regions and the closest sector of the Milky Way to our Solar System where high-mass stars are born. The nebula is named after its main star, λ Orionis, a blue giant responsible for the ionization of the surrounding material. It is also sometimes called the Angelfish Nebula due to its resemblance to an angelfish.
Observations
λ Orionis (also known as Meissa or Heka) is the star representing the head of Orion and can be found to the North of the quadrangle defined by the stars Betelgeuse, Bellatrix, Rigel and Saiph. This star can be found at the centre of open cluster Collinder 69 composed of fourth and fifth-magnitude young hot stars, visible to the naked eye. It can be resolved with a pair of binoculars. The star phi2 Orionis , an orange giant which can be seen in the southeastern sector of the cluster, is not part of this region, although it might appear to be so due to projection effects. Its distance from the Sun is, in fact, only 116 light-years, as opposed to over 1400 light-years for the cluster itself and its associated nebula. Conversely, the nebula itself is not visible with binoculars or small amateur telescopes. It becomes clearly visible in long exposure photographs.