X Crucis
X Crucis is a classical Cepheid variable star in the southern constellation of Crux.

X Crucis is a pulsating variable star with am extremely regular amplitude and period. Its apparent magnitude varies from 8.1 to 8.7 every 6.22 days. This type of variable is known as a Cepheid after δ Cephei, the first example to be discovered. X Crucis is a population I star and so is a classical or type I Cepheid variable, to be distinguished from older low-mass stars called type II Cepheid variables.

Classical Cepheids pulsate radially so that their size varies. X Crucis pulsates in its fundamental mode and its properties indicate that it is crossing the instability strip for the third time as its evolves back to cooler temperatures. Its radius varies by about during each cycle, approximately 8% of its mean radius. At the same time its temperature varies between 5,180 and 6,029 K. The radius and temperature do not vary in sync, with the smallest size occurring as the temperature is approaching its maximum. The brightness increases rapidly to a maximum when the star is hottest, then decreases more slowly. This is one of the properties that indicate fundamental mode pulsation.
Q10451997
classical Cepheid variable
Concept
Q10542
Crux
CEL
Q6243
pulsating variable
Concept
Q124313
apparent magnitude
Concept
Q188593
Cepheid
Concept
Q13024
δ Cephei
CEL
Q1436016
population I
Concept
Q10451997
classical or type I Cepheid variable
Concept
Q1393939
type II Cepheid variable
DIS
Q280157
pulsate radially
Concept
Q900488
fundamental mode
Concept
Q280157
instability strip
Concept
Q22086981
X Crucis
CEL
Q22086981
X Crucis
CEL
Q22086981
X Crucis
CEL
Q22086981
X Crucis
CEL
+8.1^^http://www.w3.org/2001/XMLSchema#decimal
8.1
NUMBER
+8.7^^http://www.w3.org/2001/XMLSchema#decimal
8.7
NUMBER
+6.22^^http://www.w3.org/2001/XMLSchema#decimal
6.22
NUMBER
+8^^http://www.w3.org/2001/XMLSchema#decimal
8
NUMBER
type of variable star
constellation
type of variable star