I was intrigued by Dr. Ben Bromleys presentation on planet building at SLAS the other night. My mind moves slowly these days so I didnt think of a coupe of questions until it was too late to ask him. I was also pleasantly suppressed at the number of intelligent questions put forth by the SLAS members and I could see that there are a good number of folks that can answer my basic questions. In Trapezium (Orion Nebula) there is one large star in the group that is surrounded by a half dozen proto-planetary discs. From what Dr. Bromley said those discs usually disappear after about 1 million years. So, Can I assume that that star is less than a million years old and it is the youngest of the group because the others don't have disc about them? A gravitational force is computed by gf = ((6.67) * m1 * m2) / (d**) m meaning mass and d meaning distance). If I have some forming planet (m1) and there are two objects (m2) & (m3) in space above the planet, m2 is 1000 times bigger than m3, and both have centers of gravity at exactly the same distance from the planet but for purposes of simplicity they are on opposites sides of the planet or otherwise situated so m2 & m3 dont attract each other, then my understanding is that m1 and m2 will have the greater gravitational force. I dont know what angular momentum or inertia might play here, but would not the bigger object hit the planet first? Like when the moon was formed, in general wouldnt the larger objects tend to coalesce out of the debris and impact the moon first? Jim Gibson --------------------------------- Do you Yahoo!? Win a $20,000 Career Makeover at Yahoo! HotJobs