The Tip of the Red Giant Branch Distance Ladder and the Hubble Constant

Understand

While the tip of the red giant branch (TRGB) has been used as a distance indicator since the early 1990's, its application to measure the Hubble Constant as a primary distance indicator occurred only recently.

• The TRGB is also currently at an interesting crossroads as results from the James Webb Space Telescope (JWST) are beginning to emerge.
• In this chapter, we provide a review of the TRGB as it is used to measure the Hubble constant.
• First, we provide an essential review of the physical and observational basis of the TRGB as well as providing a summary for its use for measuring the Hubble Constant.