How are stars represented on HR diagrams?

In an H-R diagram the luminosity or energy output of a star is plotted on the vertical axis. This can be expressed as a ratio of the star’s luminosity to that of the Sun; L*/Lsun. Astronomers also use the historical concept of magnitude as a measure of a star’s luminosity.

Where do you find Cepheids in the H-R diagram?

Cepheids occupy an elongated horizontal instability strip on the H-R diagram as massive stars transition from the main sequence to the giant and supergiant branches.

What type of stars are in the instability strip?

The instability strip is a narrow, almost vertical region in the Hertzsprung-Russell diagram which contains many different types of variable stars (RR Lyrae, Cepheid variable, W Virginis and ZZ Ceti stars all reside in the instability strip).

Where are variable stars on 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 is the hottest star on the HR diagram?

The H-R Diagram More massive main sequence stars are hotter, and are found at the top left of the strip. Less massive stars are cooler, and are found at the bottom right.

What does a HR diagram show?

Hertzsprung-Russell diagram, also called H-R diagram, in astronomy, graph in which the absolute magnitudes (intrinsic brightness) of stars are plotted against their spectral types (temperatures). The most massive stars explode in supernovas.

Do all stars become Cepheids?

Cepheid Variables All stars, late in their lifetime, change from being average stars for their mass ( main sequence stars ) to becoming swollen red giants . The stars are called Cepheids after the first star of this type to be discovered – Delta Cephei.

Where is the instability strip on the HR diagram?

The Mira instability strip on the H-R diagram is the region between mid-sized stars on the main sequence and the giant branch.

What point in an HR diagram tells us the age of a star cluster?

turnoff point
The turnoff point for a star refers to the point on the Hertzsprung-Russell diagram where it leaves the main sequence after the exhaustion of its main fuel. It is often referred to as the main sequence turnoff. By plotting the turnoff point of the stars in star clusters, one can estimate the cluster’s age.

Where is Betelgeuse on the H-R diagram?

Betelgeuse in the constellation Orion — X-axis: 3000K, Y-axis 10 5 M.

What are the classes of Cepheid variable stars?

Cepheid variables subdivide into two classes: the classical Cepheid variables, which are population I stars?stars with a high metallicity, and, therefore, of the current generation of stars?and the W Virginis variables, which are population II? stars of a low metallicity stars, and, therefore, early generation stars.

How can you tell the distance of a Cepheid variable?

Because of these properties, one can determine a distance to a Cepheid variable by measuring its period and its apparent brightness. Cepheid variables are not main sequence stars. Rather, they are stars that are in the helium burning stage of their lives.

Who is the founder of the Classical Cepheid variable?

On September 10, 1784 Edward Pigott detected the variability of Eta Aquilae, the first known representative of the class of classical Cepheid variables. However, the namesake for classical Cepheids is the star Delta Cephei, discovered to be variable by John Goodricke a month later.

How is the luminosity of a classical Cepheid related to its period?

A classical Cepheid’s luminosity is directly related to its period of variation. The longer the pulsation period, the more luminous the star.