Question

which is the celestial object which cannot be seen

Answer 1

Solution :-

The celestial objects which cannot be seen are the ones that simply do not emit light and very far from away us. Also we cannot see the asteroids, planets and stars which are very far away from our planet. 

Also, we cannot see other galaxies except our milky way galaxy with the naked eye. We will need a telescope to see them.

Answer 2

Celestial objects refer to objects present in space. While some of them can be seen with the naked eye, some can be visualized only through a telescope. The celestial objects that cannot be seen are those that have apparent magnitudes more than 6, which is the apparent magnitude limit of the human eye. Around 90% of the dark matter that is present in the universe is not visible to the naked eye.