1.   Data from Voyager II has presented astronomers with a puzzle about why our outermost planet exists.

2.   Although Earth-size planets could exist in the Upsilon Andromedae system, astronomers said, they would be undetectable with current search methods.

3.   But none of the pictures has given a clue about how far the planet, if a planet exists, is from its star.

4.   But such telescopes could do no more than tell us that the planets exist.

5.   Kepler would not only show that such planets exist, but could determine their sizes, distances from their home stars, and the length of their years.

6.   Now, new research suggests that at one time, other so-called extrasolar planets must have existed as well.

7.   Only in the past few years have we been able to determine other planets exist outside our own solar system.

8.   It is widely believed that planets such as Earth exist around other stars, but there has been no solid proof.