R Puppis (R Pup) is a

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 ...

Puppis Puppis is a constellation in the southern sky. Puppis, the Latin translation of "poop deck", was originally part of an over-large constellation Argo Navis (the ship of Jason and the Argonauts), which centuries after its initial description, was ...

. It is a rare

yellow hypergiant A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually lumino ...

and a candidate member of the

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

NGC 2439. It is also an MK spectral standard for the class G2 0-Ia.

Variability

R Puppis was identified as a variable star in 1879, and described as having a range of over a magnitude. Numerous observations over the following 100 years failed to confirm the variations, until the 1970s when clear brightness changes were observed. These were confirmed by later observations, but with a total visual amplitude of only about 0.2 magnitudes. Variable stars such as R Puppis have been described as pseudo-Cepheids, because they lie above the high-luminosity portion of 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 ...

and their variations are similar to those of Cepheids although less regular. R Puppis is formally classified as a

semiregular variable In astronomy, a semiregular variable star, a type of variable star, is a giant or supergiant of intermediate and late (cooler) spectral type showing considerable periodicity in its light changes, accompanied or sometimes interrupted by various irre ...

of type SRd, meaning F, G, or K giants or supergiants.

References

{{DEFAULTSORT:R Puppis Puppis CD-31 4910 037415 2974 062058 Puppis, R Semiregular variable stars G-type hypergiants