The Horsehead Nebula, formally known as Barnard 33, is not measured in light-years or miles. It's a dark nebula, meaning it's a cloud of dust and gas that blocks light from the stars behind it.

Here's what we can say about its size:

* Angular size: It appears about 5 light-years across in the sky.

* Actual size: It's approximately 5 light-years in diameter.

* Distance: It's located about 1,500 light-years away from Earth.

Important note: The 5 light-years refers to the apparent size as we see it from Earth. We don't know its exact shape or depth, so the actual size is an estimate based on its projected size in the sky and its distance.

Let me know if you have any more questions about the Horsehead Nebula or other astronomical objects!