Assertion: nebula's star | /r/HasProperty | sigma orionis
Facets:
Source sentences:
text: Colour images reveal a deep-red colour that originates from ionised hydrogen gas (Hα) predominantly behind the nebula, and caused by the nearby bright star Sigma Orionis.
text: The nebulosity of the Horsehead is believed to be excited by the nearby bright star Sigma Orionis.
text: What makes it so obvious is the diffuse glow from behind it; the glow is red – due to the Balmer Hα line, a prominent atomic transition in hydrogen – and is powered by the UV light from the nearby star, Sigma Orionis (which is actually a five-star system), which ionizes the hydrogen gas in this part of the Orion Complex.