Where are variable stars found in the H-R diagram?
These variable stars occupy regions on the H-R diagram known as instability strips, and plotting their variability as they transition from one evolutionary stage to another gives a better perspective of stellar evolution as a continuously changing process.
What color are stars in the instability strip?
This HR plot shows 22,000 stars from the Hipparcos Catalogue and 1,000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue.
What happens to stars in the instability strip?
Most stars more massive than the Sun enter the instability strip and become variable at least once after they have left the main sequence. It is within this region that they suffer instabilities that cause them to pulsate in size and vary in luminosity.
What does a low mass star become while it is in the instability strip?
Notice that as they evolve, HB stars cross the instability strip. For a short time, high mass stars will be Cepheid variables and low mass stars will be RR Lyrae stars.
Where are the pulsating variable stars located in the HR diagram?
Both types are located in a region of the HR Diagram called the Instability Strip. These stars take their name from δ Cephei. Most have a period of between 5 -10 days and an amplitude range of 0.5 – 2.0 magnitudes in visible light. The variations are less pronounced at infrared wavebands.
What is the instability strip of a star?
The region of the diagram enclosed in the dashed line is referred to as the instability strip. Stars that would fall in that region of the diagram will vary as described in the text above.
Where is the instability strip on the HR diagram?
It turns out that there is a certain region of the HR diagram where stars having that combination of temperature and luminosity also have the proper conditions for this pulsation to occur. That region is called the instability strip, and is labeled in the schematic HR diagram below. Figure 7.11: HR diagram with instability strip added.
What are the two types of variable stars?
The region of the diagram enclosed in the dashed line is referred to as the instability strip. Stars that would fall in that region of the diagram will vary as described in the text above. There are two types of pulsating variable stars that are particularly useful to astronomers.