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
Red Spider Nebula complex way. The central white dwarf, the remaining compact core of the original star, produces a powerful and hot (≈10,000 K) wind blowing with a speed of 300 kilometers per second, which has generated waves 100 billion kilometres high. The waves are generated by supersonic shocks formed when the local gas is compressed and heated in front of the rapidly expanding lobes. Atoms caught in the shocks radiate a visible light. These winds are what give this nebula its unique 'spider' shape and also contribute to the expansion of the nebula. The star at the center of the Red Spider