“Sirius”, the brightest star in the night sky outside our Solar System, is popularly known by which nickname based on a familiar domestic animal?

Introduction / Context:
Some of the brightest stars in the sky have traditional names and nicknames that are widely used in astronomy and popular culture. Sirius is the brightest star visible from Earth (excluding the Sun) and has been known since ancient times. It appears prominent in the constellation Canis Major, which is Latin for “Greater Dog.” Because of this, Sirius has gained a special nickname related to a domestic animal. This question asks you to recall that popular name.

Given Data / Assumptions:
- Sirius is identified as the brightest star outside the Solar System.
- It lies in the constellation Canis Major, the Great Dog.
- The options list cat star, dog star, fox star, and lion star.
- We assume standard star naming traditions used in astronomy and general knowledge.

Concept / Approach:
Because Sirius is the chief star in the constellation Canis Major, it is traditionally referred to as the Dog Star. The word “canis” itself means dog, and the constellation is often illustrated as a hunting dog in star charts. None of the other animal nicknames given in the options (cat star, fox star, lion star) are commonly associated with Sirius. While other constellations refer to lions (Leo) or other animals, the brightest star Sirius specifically belongs to the Greater Dog, making “Dog star” the correct popular name.

Step-by-Step Solution:
Step 1: Recall that Sirius is located in the constellation Canis Major. Step 2: Translate Canis Major as “the Greater Dog,” indicating a dog related association. Step 3: Recognise that Sirius has long been called the Dog Star in many cultures and texts. Step 4: Compare with other options like cat star or lion star, which do not match the constellation name. Step 5: Select Dog star as the correct nickname for Sirius.

Verification / Alternative check:
Astronomy references and star charts refer to Sirius as the Dog Star and often show it as the eye or head of the dog figure in Canis Major. Historical sources speak of the “dog days” of summer when Sirius rises with the Sun, further emphasising its dog related symbolism. No standard astronomical source labels Sirius as a cat star, fox star, or lion star. Constellations associated with lions, like Leo, have other bright stars such as Regulus, not Sirius. This confirms Dog Star as the correct answer.

Why Other Options Are Wrong:
Cat star is not a commonly used name for Sirius and does not match the meaning of Canis Major.
Fox star has no traditional association with Sirius; there is no major constellation of a fox related to this brightest star.
Lion star would more naturally be linked with the constellation Leo, not Canis Major, and is not a recognised nickname for Sirius.

Common Pitfalls:
Because the question mentions a familiar animal, some students may guess based on favourite animals instead of recalling the constellation name. The key is to connect the Latin word “canis” with dog. A simple memory aid is: Sirius sits in the “Dog” constellation, so it is the Dog Star. Remembering this link between constellation and nickname will help you confidently answer similar questions about bright stars in the night sky.

Final Answer:
Sirius is popularly known as the Dog star, because it lies in the constellation Canis Major (the Greater Dog).