kg kg http://people.cs.umass.edu/~immerman/stanford/universe.html http://people.cs.umass.edu/~immerman/stanford/universe.html http://people.cs.umass.edu/~immerman/stanford/universe.html kg http://people.cs.umass.edu/~immerman/stanford/universe.html http://people.cs.umass.edu/~immerman/stanford/universe.html http://people.cs.umass.edu/~immerman/stanford/universe.html http://people.cs.umass.edu/~immerman/stanford/universe.html kg the mass http://people.cs.umass.edu/~immerman/stanford/universe.html