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Spica A
Details
Spica A is the hot blue primary in the Spica binary and a Beta Cephei variable near the end of its main-sequence life. Its rapid rotation and close companion distort the star into an ellipsoidal shape, so the system appears to breathe and shimmer even though the stars remain unresolved to the naked eye.
Spica A is the kind of star that refuses to look perfectly round for long. It is the hot blue primary in a binary system, and its surface is being pulled and reshaped by a combination of rapid rotation and a close companion. That gives the star a sense of motion even when it is seen only as a point of light.
The result is a system that is visibly active. Spica A is a Beta Cephei variable, so it belongs to a class of stars whose brightness changes in a structured way, while its ellipsoidal shape tells you the star is under real physical stress. This is not quiet constancy; it is a star whose geometry and behavior both betray the forces acting on it.
That is why Spica A is so compelling. It shows that some stars are most interesting when they look slightly unstable. Instead of presenting a simple, steady glow, Spica A gives astronomy a living reminder that rotation, companionship, and internal physics can all leave a visible mark on a star.
3.86million km
Visual creditscaleofspace.org / CC BY-NC 4.0
Key facts
- Category
- Stars
- Object class
- B-type giant/subgiant star
- Mass
- ~11.4 solar masses
- Host
- Spica system
- Scale fact
- 10.4 million kmdiameter
- Estimated age
- ~12.5 million years
- Composition
- Hydrogen and helium
- Temperature
- ~25,300 K surface
Scale context
Where Spica A sits on the full axis
Shared physical scale
40.8million km
Together, these objects make the size change around Spica A easy to compare at a glance.
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.