SV Vulpeculae is a

classical Cepheid Classical Cepheids (also known as Population I Cepheids, Type I Cepheids, or Delta Cepheid variables) are a type of Cepheid variable star. They are population I variable stars that exhibit regular radial pulsations with periods of a few days to a ...

(δ Cepheid)

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Vulpecula Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is commonly known simply as the fox. It was identified in the seventeenth century, and is located in the middle of the Summer Triangle (an ...

. It is a

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spa ...

at a distance of 8,700 light years. SV Vulpeculae is a δ Cepheid variable whose visual

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

ranges from 6.72 to 7.79 over 45.0121 days. The light curve is highly asymmetric, with the rise from minimum to maximum taking more less than a third of the time for the fall from maximum to minimum. The period has been decreasing on average by 214 seconds/year. SV Vulpeculae is a yellow

bright supergiant In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

around twenty thousand times as luminous as the sun, with a spectral type that varies from late F to early K. It pulsates and varies in temperature from below 5,000 K to above 6,000 K. The radius is at maximum, and varies from to as the star pulsates. The mass of SV Vulpeculae is now near , and is estimated to have been about when it was on the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

. The rate of change of the period and the atmospheric abundances show that the star is crossing the

instability strip The unqualified term instability strip usually refers to a region of the Hertzsprung–Russell diagram largely occupied by several related classes of pulsating variable stars: Delta Scuti variables, SX Phoenicis variables, and rapidly oscillati ...

for the second time. The first instability strip crossing occurs rapidly during the transition from the main sequence to becoming a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Anta ...

. The second crossing occurs during core helium burning when the star executes a

blue loop In the field of stellar evolution, a blue loop is a stage in the life of an evolved star where it changes from a cool star to a hotter one before cooling again. The name derives from the shape of the evolutionary track on a Hertzsprung–Russell ...

, becoming hotter for a time before returning to the red supergiant stage.

References

{{DEFAULTSORT:SV Vulpeculae Vulpecula Classical Cepheid variables Vulpeculae, SV G-type supergiants 187921 F-type supergiants K-type supergiants 097717 Durchmusterung objects