What causes Cepheid stars to pulsate?

A Cepheid pulsates in a regular and predictable cycle. It is thought that Helium is involved in its cycle. Doubly ionized Helium is more opaque than singly ionized helium, meaning it lets little light through. At the dimmest part of the cycle, doubly ionized Helium makes up the outer layers of the star.

What is the cause of the luminosity changes of variable stars?

There are a number of reasons for variability. These include changes in star luminosity or in star mass, and obstructions in the amount of light that reaches Earth. Intrinsic variables are stars whose luminosity physically changes due to pulsations, eruptions or through swelling and shrinking.

What is happening when a Cepheid variable star pulsates?

A Cepheid variable (/ˈsɛfiːɪd, ˈsiːfiːɪd/) is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.

What is meant by a pulsating star?

Definition of pulsating star : a star that alternately increases and decreases in size usually with corresponding changes in brightness.

Why do Mira variables pulsate?

Mira variables are stars massive enough that they have undergone helium fusion in their cores but are less than two solar masses, stars that have already lost about half their initial mass. They are pulsating due to the entire star expanding and contracting.

What is a pulsating star quizlet?

pulsating variable star. a variable star that pulsates in size and luminosity.

What is the luminosity class of a star?

Luminosity class 0 or Ia+ is used for hypergiants, class I for supergiants, class II for bright giants, class III for regular giants, class IV for subgiants, class V for main-sequence stars, class sd (or VI) for subdwarfs, and class D (or VII) for white dwarfs.

What causes the expansion and contraction of Cepheids?

In ordinary stars, hydrostatic equllibrium diminishes these pulsations. Basically, Starr’s in this stage can create conditions that trap their radiated energy in the outer layers. The pressure increases enough so that the outer layers expand.

What is the meaning of pulsating theory?

Definition of pulsation theory : a theory that explains the peculiar features of such stars as the Cepheid variables by assuming an expansion and contraction of the star as a whole in a regular periodic pulsation.

What is stellar parallax used for?

Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax. Simply put, they measure a star’s apparent movement against the background of more distant stars as Earth revolves around the sun.