Bag said their planet was twice as big as earth, so she should have been hopping into the air every time she took a step, due to the reduced gravity of the planet. And obviously this race, despite their advanced technology, can't adjust to gravity differentials well, since that's what was killing their planet to start with.
shareLol... are you serious?
If the gravity on her planet is twice that of earth's she would weigh probably 260 pounds there, but she'd still be 130 on Earth. People bounce around on the moon because the gravity is about 1/6 of here. Get it?
Size does not only matter when it comes to how strong gravity is.
How strong gravity is on a planet is found in radius + mass + density
That's how they found out how much gravity there is on the planets in our own solar system, from the smallest to the largest.
A little science fact about the planets and their gravity in our solar system.
http://www.universetoday.com/35565/gravity-on-other-planets/
So yes, Celeste can easily come from a planet twice the size of Earth, who has the same amount of gravity.