A visually striking collection of interstellar gas and dust is captured in this latest image from the NASA/ESA Hubble Space Telescope. Named RCW 7, this nebula is located over 5,300 light-years away in the constellation Puppis.
Nebulae, such as RCW 7, are rich in the raw materials needed to form new stars. Under the influence of gravity, parts of these molecular clouds collapse, coalescing into very young, developing stars known as protostars. These protostars remain surrounded by spinning discs of leftover gas and dust. In RCW 7, the forming protostars are particularly massive, emitting strong ionizing radiation and fierce stellar winds that transform the nebula into an H II region.
H II regions are characterized by hydrogen ions; H I denotes a normal hydrogen atom, whereas H II is hydrogen that has lost its electron, becoming an ion. Ultraviolet radiation from the massive protostars excites the hydrogen in the nebula, causing it to emit light, resulting in the nebula’s soft pinkish glow.
The Hubble data for this image were collected from a study of a particularly massive protostellar binary named IRAS 07299-1651. This binary is still cocooned in gas within the curling clouds toward the top of the image. To expose this star and its siblings, astronomers utilized Hubble’s Wide Field Camera 3 in near-infrared light. While the massive protostars are brightest in ultraviolet light, they emit substantial infrared light as well. Infrared light’s longer wavelength allows it to penetrate much of the gas and dust, enabling Hubble to capture this stunning image. Many of the larger stars seen in the image are actually foreground stars, positioned between the nebula and our solar system, and are not part of the nebula.
The formation of an H II region signals the beginning of the end for a molecular cloud like RCW 7. Within a few million years, radiation and winds from the massive stars will gradually disperse the nebula’s gas. This process will be accelerated by supernova explosions as the most massive stars reach the end of their lives. New stars in this nebula will incorporate only a fraction of its gas, with the remainder spreading throughout the galaxy to eventually form new molecular clouds.