1.   And recent analyses indicate that such skirmishes were much more intense around the time the planets were forming.

2.   Another possibility is that occasionally a massive planet does form in such a close-in location, contrary to the estimates based on recent theory.

3.   After the planets formed, their gravitational pull interfered with the orbits of leftover building blocks called planetesimals.

4.   But Chen said that the evidence was insufficient to determine if the dust disk was a remnant of planet formation or a place where planets could form.

5.   Did this undermine the prevailing theory that planets form by a snowball effect of growth from small ones to large bodies?

6.   Out of the dozens of e-mail messages he has been getting every day he has seen at least four theories explaining how this planet formed.

7.   Scientists now know, for instance, that if the law of gravity was even slightly stronger or weaker, planets could not form in stable orbits around stars.

8.   The more new stars that form, the more chances there are that planets will also form.

9.   The Saturnian ring system reminds scientists of what the early solar nebula must have looked like at the time the planets were forming.

10.   Theorists believe the planets formed from collisons of bits of ice and dust, which coalesced into ever larger chunks, and eventually into the planets.