The biggest single object in the observable universe is the **observable universe itself.** The observable universe is the vast expanse of space that we can see and detect with our current technology. It includes galaxies, stars, planets, cosmic structures, and everything that can be observed from Earth.
The observable universe has a radius of about 46.5 billion light-years, which means that the farthest objects we can observe are approximately 46.5 billion light-years away from us. This distance is not a measure of the age of the universe but is a result of the expansion of space.
It's important to note that the observable universe is just a fraction of the entire universe. The actual size and extent of the entire universe, beyond what we can observe, remain unknown. The observable universe is limited by the distance that light has had time to travel since the beginning of the universe, which is about 13.8 billion years. Anything beyond this cosmic horizon is not currently visible to us.