Who am I - Astronomy

I am a tiny planet, I mostly orbit between Mars and Jupiter, Who am i?

I'm a doughnut-shaped concentration of asteroids my asteroids orbit the Sun between the orbits of Mars and Jupiter, Who am I

I go up in space to explore, Who am I

I study astronomy and I learn about objects in the universe, Who am I

I am science that studies the universe, Who am I

My gas surrounds a planet, Who am i?

Everything is made of me, Who am I

I am a beautiful light and I live in the near-polar sky, Who am I

I have 7 stars contained in the Northern Hemisphere constellation Ursa major, Who am I

I'm a thousand million, Earth is thousand millions of years old