The Orion molecular cloud complex (or, simply, the Orion complex) is a star-forming region with stellar ages ranging up to 12 Myr. Two giant molecular clouds are a part of it, Orion A and Orion B. The stars currently forming within the complex are located within these clouds. A number of other somewhat older stars no longer associated with the molecular gas are also part of the complex, most notably the Orion's Belt (Orion OB1b), as well as the dispersed population north of it (Orion OB1a). Near the head of Orion there is also a population of young stars that is centered on Meissa. The complex is between 1 000 and 1 400 light-years away, and hundreds of light-years across. The Orion complex is one of the most active regions of nearby stellar formation visible in the night sky, and is home to both protoplanetary discs and very young stars. Much of it is bright in infrared wavelengths due to the heat-intensive processes involved in stellar formation, though the complex contains dark nebulae, emission nebulae, reflection nebulae, and H II regions. The presence of ripples on the surface of Orion's molecular clouds was discovered in 2010. The ripples are a result of the expansion of the nebulae gas over pre-existing molecular gas. The Orion complex includes a large group of bright nebulae, dark clouds in the Orion constellation. Several nebulae can be observed through binoculars and small telescopes, and some parts (such as the Orion Nebula) are visible to the naked eye. Nebulae within the complex The following is a list of notable regions within the larger complex: Orion A molecular cloud The Orion Nebula, also known as M42 (part of Orion's Sword) M43, which is part of the Orion Nebula Sh2-279 (part of Orion's Sword) NGC 1980 (part of Orion's Sword) Orion molecular cloud 1 (OMC-1) with the Becklin–Neugebauer Object and the Kleinmann–Low Nebula Orion molecular cloud 2 (OMC-2) Orion molecular cloud 3 (OMC-3) Orion molecular cloud 4 (OMC-4) NGC 1981 NGC 1999 LDN 1641 HH 1/2, the first recognized Herbig–Haro objects HH 34 a Herbig–Haro object with symmetric bow shocks Orion B molecular cloud Flame Nebula (NGC 2024) IC 434, which contains the Horsehead Nebula The Horsehead Nebula (Barnard 33) M78, a reflection nebula (NGC 2068) McNeil's Nebula is a variable nebula discovered in 2004 near M78 Orion East Cloud (LDN 1621 + LDN 1622) HH 24-26 this