What are Cepheid variables used for?

Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years. a uniform function of their brightness.

How are Cepheid variables used to measure distance?

Through observations of Cepheid variables, astronomers have determined the distances to other galaxies. They compare the Cepheid variable’s apparent brightness with its intrinsic brightness. The difference between observed and actual brightness yields the distance.

What is a Cepheid variable star and why is it important in astronomy?

Named after delta-Cephei, Cepheid Variables are the most important type of variable because it has been discovered that their periods of variability are related to their absolute luminosity. This makes them invaluable as a contributer to astronomical distance measurement.

Why are Cepheid variables called Cepheids?

Cepheid variable stars were named after the first of their kind observed, δ Cepheus. There are actually two classes of Cepheid: Type I Cepheids (δ Cepheus is a classical Cepheid) are population I stars with high metallicities, and pulsation periods generally less than 10 days.

Are Cepheids rare?

Cepheids are rare stars, and so they are typically far away and we don’t have parallaxes for many. Some Galactic Cepheids have parallaxes from the Hubble Space Telescope, so their luminosities are accurately known, others we can get distances for using main sequence fitting or other distance measures.

What did Henrietta Swan Leavitt study?

Henrietta Swan Leavitt was a Harvard “computer” — one of several women in the early 1900s who studied photographic plates for fundamental properties of stars. Leavitt is best known for discovering about 2,400 variable stars between 1907 and 1921 (when she died).

Why are Cepheids used as standard candles?

Cepheid variable stars are stars that appear to pulsate over regular intervals. If astronomers can measure the period of a Cepheid variable, they can calculate the absolute magnitude of the star, making Cepheid variables standard candles.

Why do Cepheids pulsate?

But why does the star pulsate at all?? When a Cepheid is compressed, it becomes opaque. Photons are trapped inside, heating the gas and increasing its pressure. The high-pressure gas expands, becoming transparent. Photons escape, the gas cools, the pressure drops.

What is Cepheid variables luminosity relationship?

Cepheid variable stars are intrinsic variables which pulsate in a predicatable way. In addition, a Cepheid star’s period (how often it pulsates) is directly related to its luminosity or brightness. Cepheid variables are extremely luminous and very distant ones can be observed and measured.

What is the meaning of Cepheids?

Definition of Cepheid : any of a class of variable stars whose very regular light variations are related directly to their intrinsic luminosities and whose apparent luminosities are used to estimate distances in astronomy.

What are the cephieds used for?

Cepheids , also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years.

What are predictive variables?

Predictive Variables. The variables that are part of the formula comprising elements of a credit-scoring model. These variables are used to predict a borrower’s future credit performance.

What is a cephiad variable star?

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. Type II Cepheids (also termed Population II Cepheids) are population II variable stars which pulsate with periods typically between 1 and 50 days.

What does Cepheid mean?

A Cepheid is a member of a class of very luminous variable stars. The strong direct relationship between a Cepheid variable’s luminosity and pulsation period secures for Cepheids their status as important standard candles for establishing the Galactic and extragalactic distance scales.