You have to get to where your ship (The Normandy) is stationed on that planet to leave it.
If he died in Mass Effect 1 then he is not in Mass Effect 2. If he survived Mass Effect 1 he shows up in Mass Effect 2 but he can not be killed.
Yes, the number of moons can affect the mass of a planet to some extent, as the gravitational pull between the planet and its moons can influence each other. However, the effect is usually minimal compared to the mass of the planet itself.
He's on Omega.
No. A planet's gravitational pull is determined by the planet's mass. A planet's orbital speed is determined by the the mass of the Sun and the planet's distance from the Sun.
yes
No, Mass Effect 2 has a completely different weapon system.
Not necessarily free roam. Its hopping from planet to planet, with somewhat of a linear structure.
Yes. Mass Effect is a good game series and you should start playing the Mass effect 1 on PS 3.
Yes.
The Normandy Crash site is located on the planet Alchera (Amada system, Omega Nebula) in Mass Effect 2
Yes, a planet's mass can be determined by observing its transit across a star. By measuring the dip in the star's brightness during the transit, astronomers can calculate the size of the planet and its gravitational effect on the star, which provides information on the planet's mass.
If you played Mass Effect 1 the second game imports your old game save, so it would depend on how you played Mass Effect 1 as to whether or not Kaiden is alive. If you did not play Mass Effect 1, then the game will default to the character with the opposite gender to Shepard. So Ashley will be there with a male Shepard, Kaiden for a female one. Below is a link which has the important decisions you make in 1 and their effect in the sequel.