The Orion Nebula (M42)

The Great Orion Nebula (M 42). The nebula consists primarily of hydrogen (about 90%) and helium (about 10%), with small traces of heavier elements. It contains interstellar dust, as well as young stars of various spectral classes and protostars at different stages of formation. Its apparent magnitude is about 4m, making the nebula visible to the naked eye. At the center of the nebula is a young open star cluster—the Trapezium of Orion—whose brightest stars illuminate the nebula and ionize its material.