Once a star is fully formed, it doesn't *become* a specific type of star. It's already a star, but it's classified into a spectral type based on its temperature, size, and luminosity.

Here's how it works:

* Formation: A star forms from a cloud of gas and dust.

* Main Sequence: Once the star ignites nuclear fusion in its core, it enters the main sequence stage. This is the longest part of a star's life.

* Spectral Classification: During the main sequence, stars are classified into spectral types (O, B, A, F, G, K, M) based on their surface temperature, which is indicated by the color of light they emit.

Example: Our Sun is a G-type star, meaning it's relatively cool and yellow.

Other Stellar Stages:

Stars can evolve beyond the main sequence, becoming red giants, supergiants, white dwarfs, neutron stars, or black holes depending on their mass.

So, the answer isn't a specific type of star, but rather a classification based on its characteristics.