The constellation that serves as the background stars of the Sun in the sky changes throughout the year as the Earth orbits the Sun. This is because our perspective of the stars changes as we move around the Sun.

There's no one specific constellation that the Sun is always "in".

To determine the constellation behind the Sun at any given time, you would need to know the exact date and time.

For example:

* On March 21st, the Sun is in the constellation Pisces.

* On June 21st, the Sun is in the constellation Gemini.

* On September 23rd, the Sun is in the constellation Virgo.

* On December 21st, the Sun is in the constellation Sagittarius.

You can use online tools or star charts to find the constellation behind the Sun for any specific date.