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The 52 pages that link to H II region, each with the reason it gives.

• Interstellar mediumBroader topic: Ultraviolet radiation from massive stars transforms nearby gas into an expanding ionized region.

• Supernova remnantCompared with: Both can appear as glowing gas clouds, but an H II region is energized by stellar radiation rather than supernova debris.

• Planetary nebulaCompared with: Both glow through photoionized gas, but H II regions are powered by young stars, not stellar remnants.

• Stellar feedbackBroader topic: It is a common structure formed as stellar radiation ionizes and expands surrounding gas.

• ReionizationBroader topic: Early H II regions expanded around sources and eventually overlapped across the intergalactic medium.

• Orion NebulaNarrower topic: Ultraviolet light from the Trapezium stars ionizes much of the nebula’s hydrogen.

• Massive starRelated: Massive stars power bright H II regions around their birth sites.

• Emission nebulaBroader topic: Many emission nebulae are H II regions, with hydrogen ionization driving their visible light.

• Herbig–Haro objectCompared with: Its gas is primarily ionized by starlight, unlike the shock-powered emission in these objects.

• Small Magellanic CloudRelated: These star-forming nebulae illuminate active regions within the galaxy.

• NebulaBroader topic: Its glowing ionized gas defines many bright emission nebulae.

• Hydrogen spectrumRelated: Recombining hydrogen produces characteristic emission lines in these nebulae.

• Spiral armBroader topic: Bright H II regions mark sites of recent star formation along many arms.

• Neutral hydrogenCompared with: It marks environments where ultraviolet light has converted neutral atoms into protons and electrons.

• Carina NebulaNarrower topic: Ionized hydrogen glows across much of the nebula where massive stars energize its gas.

• Magellanic CloudsRelated: Bright H II regions trace sites of recent star formation in the Clouds.

• Star formation rateRelated: Its emission traces ionizing radiation from massive stars formed within roughly the past few million years.

• Grand-design spiral galaxyRelated: These luminous regions reveal where spiral arms host recent massive-star formation.

• Interstellar magnetic fieldBroader topic: Its ionized gas makes magnetic-field diagnostics such as Faraday rotation accessible.

• O-type starRelated: New O-type stars ionize their birth clouds and illuminate these regions.

• PhotoevaporationBroader topic: Photoevaporating cloud edges help shape these expanding regions around massive stars.

• Eagle NebulaRelated: Its glowing hydrogen marks gas ionized by the cluster’s ultraviolet light.

• Tarantula NebulaNarrower topic: Ionized hydrogen gives much of the nebula its glowing appearance.

• Triangulum GalaxyRelated: M33’s disk contains prominent regions where young stars ionize surrounding gas.

• Bok globuleCompared with: Bright ionized gas contrasts with the dark silhouette of a Bok globule against illuminated nebulae.

• Cartwheel GalaxyBroader topic: Bright knots in the Cartwheel’s ring include regions where newly formed stars ionize gas.

• Flocculent spiral galaxyRelated: Bright H II regions mark the scattered sites of recent star formation in spiral arms.

• Luminous infrared galaxyCompared with: Such regions mark star formation locally, but do not by themselves constitute an infrared-luminous galaxy.

• Magellanic BridgeBroader topic: Such regions mark sites where stars have formed within the Bridge.

• Reflection nebulaCompared with: Its hydrogen emission can distinguish it from adjacent dust-scattered glow.

• Messier 83Broader topic: Bright H II regions mark sites where new stars are forming in Messier 83.

• Perseus ArmRelated: These luminous regions mark sites of recent massive-star formation along the arm.

• Pillars of CreationRelated: The pillars stand within the Eagle Nebula’s ionized gas, whose radiation drives their erosion.

• Galactic planeBroader topic: These luminous star-forming regions mark parts of the galactic plane.

• H I regionCompared with: Ionization distinguishes H II regions from predominantly neutral H I regions.

• Lagoon NebulaRelated: Ionized hydrogen produces much of the Lagoon Nebula’s characteristic red emission.

• ProplydNarrower topic: Many observed proplyds sit inside the Orion Nebula’s ionized H II region.

• R136Related: The cluster’s radiation ionizes gas throughout the surrounding Tarantula Nebula.

• Rosette NebulaNarrower topic: The Rosette is a prominent example of this kind of emission nebula.

• Pinwheel GalaxyBroader topic: Bright H II regions trace star-forming sites across the galaxy’s spiral arms.

• High-velocity cloudCompared with: It is an ionized nebula, unlike the neutral hydrogen traced in high-velocity clouds.

• Interstellar cloudBroader topic: Ultraviolet light from young massive stars ionizes and reshapes nearby cloud gas.

• Low-ionization nuclear emission-line regionCompared with: H II regions are powered by massive stars and usually occupy a different diagnostic locus.

• Omega NebulaNarrower topic: The Omega Nebula is an H II region whose hydrogen glows under ultraviolet radiation.

• Trapezium ClusterRelated: Radiation from the cluster’s massive stars creates the surrounding ionized gas.

• Trifid NebulaRelated: Ultraviolet radiation from young stars ionizes hydrogen in the Trifid’s glowing gas.

• Astronomical radio sourceBroader topic: Its warm plasma emits thermal radio waves and can reveal obscured star formation.

• Plasma recombinationBroader topic: Hydrogen recombination produces characteristic emission used to study these nebulae.

• Starburst regionBroader topic: These glowing nebulae mark recent massive-star formation within starbursts.

• Stochastic self-propagating star formation modelBroader topic: These regions mark recent massive-star formation and can reveal its spatial progression.