Depends, sometimes planets, stars, meteos.. paper flying lanters that people lite up them selves, sattelites, comets, flying bats, and witches on broomsticks.
As seen from Earth in the night sky, all objects change their position. There is also the factor of the Earth's rotation. Most objects in the sky ... day or night ... appear to rise in the east and travel across the sky toward the west. (You may have noticed the daily behavior of the sun.) So when Uranus can be seen, the direction to look for it in will depend on the time and also where you are on the Earth, as that too can make a difference. There are many websites, like Heavens-Above.com which will give you locations of objects in the night sky when they can be seen.
there are not any in the sky in mars at night discovered
They are objects in the sky
Rigel has been visible in the night sky for over 8 million years. It would have been seen by the first creatures who looked up into the night sky. So no one can be said to have discovered Rigel.
Algol has been visible in the night sky for over 300 million years. It would have been seen by the first creatures who looked up into the night sky. So no one can be said to have discovered Algol.
depends on where you are
comets.
There's only one difference between the sky seen from the Earth and the sky seen from the moon. The sky seen from the Earth has a moon in it, and the sky seen from the moon has an Earth in it. Other than that, exactly the same objects in the same patterns are seen from both places.
the night sky
at night.
the sunlight
The sun.