What makes a star a Cepheid?

Cepheid stars are stars that have evolved off the main sequence into the Cepheid instability strip. They are regular radial-pulsating stars, with a well-defined period-luminosity relationship, which makes them ideal stars to be used as primary distance indicating standard candles.

What is a Cepheid variable astronomy?

Cepheid variable, one of a class of variable stars whose periods (i.e., the time for one cycle) of variation are closely related to their luminosity and that are therefore useful in measuring interstellar and intergalactic distances.

What is special about Cepheid variable stars?

Cepheids Variables are special type of variable star in that they are hot and massive – five to twenty times as much mass as our Sun – and are known for their tendency to pulsate radially and vary in both diameter and temperature.

What makes a star variable?

A star is considered variable if its apparent magnitude (brightness) is altered in any way from our perspective on Earth. These changes can occur over years or just fractions of a second, and can range from one-thousandth of a magnitude to 20 magnitudes.

What is a Cepheid variable star quizlet?

Cepheid variable are. Stars whose luminosity varies regularly with a period of several days. Unstable stars. Their size is oscilsting (EXPANDING AND CONTRACTING) As the size changes, so does their luminosity and surface temperature.

Why are Cepheids useful?

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.

Is Barnard’s star hotter than the sun?

Even so, the lower mass of Barnard’s Star makes it about 2,500 times less powerful than our sun. In other words, Barnard’s Star is much dimmer and cooler than our sun.

What describes an elliptical galaxy?

An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are preferentially found close to the centers of galaxy clusters. Elliptical galaxies range in size from tens of millions to over one hundred trillion stars.

What are two types of variable stars?

There are two different categories of variable stars. Intrinsic variables are stars whose luminosity physically changes due to pulsations, eruptions or through swelling and shrinking. Extrinsic variables are stars that change in brightness because of being eclipsed by stellar rotation or by another star or planet.

Why do Cepheid stars pulsate?

When a star enters a phase during which it has the right combination of temperature and size, it will pulsate. In other words, many many stars will be Cepheids at some point during their life cycle. The ones we see now are just the stars that happen to be in the right part of the life cycle now.

How do Cepheid stars pulsate?

Cepheid variable stars are stars that periodically pulsate because of an instability in their internal structure. They grow brighter and dimmer on a regular cycle as they pulsate radially, alternately become physically larger and then smaller. Their brightening is partly a consequence of their larger surface area.

What is the distance from Earth to Polaris?

Polaris is approximately 430 light years from Earth and is the brightest star in the constellation of Ursa Minor . Polaris is a three star system comprising of the supergiant Polaris A and two smaller companions.