1) The word "mountain" contains three vowels: O, U, and A.

2) The word "guitar" contains three vowels: U, A, and I.

3) Michael Jackson's album "Thriller" is the best-selling album of all time, with estimated sales of over 66 million copies worldwide.

4) The Hubble Space Telescope, launched in 1990, has provided breathtaking images of distant galaxies and deep space.