The Heart of the matter

 

IC 1805 and Melotte 15.

"The above images captured at the Jodrell Plank Observatory and also by the PIRATE robotic telescope on Mount Teide, Tenerife (credit telescope .org, Open Observatories, Open University) show the Heart Nebula, IC1805 in increasing detail and reducing field of vision. The top, widefield image was captured with the JPOs modded Canon 200d Camera with a Dual Band filter and a Samyang 135mm lens. The other two were captured by the PIRATE telescope with SHO filters. Pip Stakkert used a number of processing techniques to emphasise the nebulosity". - Kurt Thrust current Director of the JPO.

"The Heart Nebula (IC 1805) is a large emission nebula located in the Perseus Arm of the Milky Way, within the constellation Cassiopeia. At an estimated distance of approximately 6,000–7,500 light-years from Earth, it extends over nearly 200 light-years in diameter, making it one of the more prominent star-forming complexes in the northern sky. Its common name derives from the overall morphology of its extended H II region, which, in wide-field optical images, presents an outline reminiscent of a stylized human heart.

The nebula is primarily excited by the young stellar population of the open cluster Melotte 15, situated near the nebula’s center. This cluster, containing numerous hot O-type and early B-type stars, serves as the dominant ionizing source for the surrounding gas. The intense ultraviolet radiation emitted by these massive stars ionizes the hydrogen in the surrounding molecular cloud, producing the characteristic red glow of Hα emission. Stellar winds and radiation pressure also drive large-scale feedback processes that shape the morphology of the nebula, generating bright ridges, cavities, and dark, pillar-like structures of dense gas.

Of particular note is the brighter nebulosity concentrated near the nebula’s core. This region surrounds Melotte 15 and exhibits a higher surface brightness due to the proximity of the ionizing sources and the resulting density contrast between ionized and neutral gas. Within this core, the interplay between radiation, stellar winds, and turbulence has carved out intricate filaments and luminous fronts, where shock compression has enhanced local gas densities. These conditions are conducive to ongoing star formation: observations at infrared and radio wavelengths reveal embedded protostars and compact H II regions tracing younger generations of stellar objects still enshrouded in dust.

In summary, IC 1805 exemplifies the dual role of massive stars in galactic ecology: while their radiation and winds sculpt and erode the parent molecular cloud, they also trigger subsequent episodes of star formation. The central bright nebulosity of the Heart Nebula, therefore, represents not only a visually striking concentration of emission but also the dynamic hub of stellar feedback and continuing stellar genesis within the complex". -Professor G.P.T Chat and Karl Segin outreach coordinator at the JPO.