The Cave Nebula, Sharpless 155 or LBN529 in the Constellation Cepheus

 

The Cave Nebula (Emission Nebula) Seestar S30 LP filter EQ mode 181x60 sec exposures. Credit: Kurt Thrust at the JPO.

" The Cave Nebula is riding high in the sky over Lowestoft and a clear night delivered 3 hours of unbroken photon capture from the Constellation Cepheus. The whole JPO Team thought this was an interesting and beautiful emission nebula. Kurt has been trying out the AffinityPhoto 3 freeware and James Rison's V20 Astro- macros. He used both on the above image for stacking and processing. Both Kurt and Pip Stakkert are impressed by the quality of this useful software. AFF 3 and V20 offer significant improvements and add-ons over previous iterations. Well done CANVA and James!!" - Joel Cairo CEO of the Jodrell Plank Observatory.

The thoughts of our Coms Manager Gary Gemini:

"Unveiling the Cave Nebula (Sh2-155 / Caldwell 9) in Cepheus

Nestled deep within the rich stellar fields of the northern constellation Cepheus lies one of the most visually striking and dynamically complex stellar nurseries in our night sky: the Cave Nebula, catalouged as Sharpless 155 (Sh2-155) or Caldwell 9. Captured here in striking detail, this celestial landscape offers a breathtaking window into the violent, creative processes of star formation.

Distance and Scale

The Cave Nebula resides at an approximate distance of 2,400 light-years from Earth, placing it firmly within the Perseus Arm of the Milky Way as part of the massive Cepheus molecular cloud complex. Across the sky, the prominent emission region spans an apparent area of roughly 50 by 30 arcminutes. Physically, the distinct, cavernous structure that gives the nebula its name stretches roughly 10 light-years across, while sitting at the edge of a much larger, sprawling complex of glowing gas and obscuring dust lanes.

Structure and Interesting Features

True to its name, the Cave Nebula is famous for its distinct, dark, hollow silhouette carved out of dense cosmic dust and gas. This dark indentation is sharply bounded by bright, glowing rims of ionized hydrogen gas (an H II region). These luminous borders are energized by intense ultraviolet radiation pouring from hot, young OB-type stars residing nearby—particularly those associated with the Cepheus OB3 association.

The region is a masterclass in mixed nebulosity, seamlessly blending three distinct types of nebulae into a single frame:

Emission Nebulae: The brilliant red and pink expanses glowing as hydrogen atoms are ionized and recombine.

Reflection Nebulae: Subtle blue regions where starlight scatters off microscopic dust particles.

Dark Nebulae: Impenetrable, dense dust lanes that obscure background stars and create the dramatic contours of the "cave".

Active Star Formation

Beyond its aesthetic appeal, Sh2-155 is a site of active, ongoing star birth. Multi-wavelength studies—including observations by space-based observatories like Chandra and Spitzer—have revealed a gradient of stellar ages across the region. The compression wave generated by radiation and stellar winds from older generation stars crashing into the dense molecular cloud (Cepheus B) is actively triggering the collapse of new material, sparking a fresh wave of protostellar evolution right along the edges of the dark cave. "