Tip of the red-giant branch result is a sharp discontinuity in the evolutionary track of the star on the HR diagram. This discontinuity is called the tip of the red-giant branch. When distant stars at the TRGB are measured in the I-band (in the infrared), their luminosity is somewhat insensitive to their composition of elements heavier than helium (metallicity) or their mass; they are a standard candle with an I-band absolute magnitude of –4.0±0.1. This makes the technique especially useful as a distance indicator. The TRGB indicator uses stars in the old stellar populations (Population II). Tip of the red-giant branch Tip of the red-giant
Ice giant by extreme ultraviolet (EUV) radiation emitted by θ Orionis C suggests another possible mechanism for the formation of ice giants. Multiple-Jupiter-mass gas-giant protoplanets could have rapidly formed due to disk instability before having the majority of their hydrogen envelopes stripped off by intense EUV radiation from a nearby massive star. In the Carina Nebula, EUV fluxes are approximately 100 times higher than in Trapezium's Orion Nebula. Protoplanetary disks are present in both nebulae. Higher EUV fluxes make this an even more likely possibility for ice-giant formation. The stronger EUV would increase the removal of the gas envelopes from the protoplanets