Tip of the red-giant branch
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a1/Evolutionary_track_1m.svg/260px-Evolutionary_track_1m.svg.png)
Tip of the red-giant branch (TRGB) is a primary distance indicator used in
Method
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/c9/M5_colour_magnitude_diagram.png/260px-M5_colour_magnitude_diagram.png)
The Hertzsprung–Russell diagram (HR diagram) is a plot of stellar luminosity versus surface temperature for a population of stars. During the core hydrogen burning phase of a Sun-like star's lifetime, it will appear on the HR diagram at a position along a diagonal band called the main sequence. When the hydrogen at the core is exhausted, energy will continue to be generated by hydrogen fusion in a shell around the core. The center of the star will accumulate the helium "ash" from this fusion and the star will migrate along an evolutionary branch of the HR diagram that leads toward the upper right. That is, the surface temperature will decrease and the total energy output (luminosity) of the star will increase as the surface area increases.[2]
At a certain point, the helium at the core of the star will reach a pressure and temperature where it can begin to undergo nuclear fusion through the
When distant stars at the TRGB are measured in the
See also
References
- S2CID 67754889.
- ^ ISBN 978-1-56881-012-6.
- Bibcode:1999IAUS..183...48S.
- S2CID 121612286.
External links
- "Tip of the Red Giant Branch as a Distance Indicator". Shoko Sakai, Research Astronomer, Division of Astronomy and Astrophysics, University of California, Los Angeles. Archived from the original on 26 February 2005. Retrieved February 14, 2005.
- "NASA Hubble Space Telescope Daily Report # 3431". SpaceRef. 21 August 2003. Retrieved February 14, 2005.[permanent dead link]