The question is, can a Jedi Lightsaber cut through Superman?
The question is, can a Jedi Lightsaber cut through Superman? To answer this, we need to look at some raw data for both lightsabers and Superman himself.
Short Answer: No
A Jedi Lightsaber is plasma contained in a magnetic field. Plasma is basically the form of matter which stars are made o. Pre-Crisis Superman has flown through the heart of a star without being harmed, therefore, he is immune to plasma.
Post-Crisis Superman was not as invulnerable. For example, a nuclear explosion would weaken him. Assuming a lightsaber contains power similar to a nuclear explosion, it could similarly disrupt his invulnerability during impact (See Force of Impact below).
Superman received his power from the radiation of our yellow sun, and is weakened when exposed to radiation from a red sun. It is possible that a Sith lightsaber, being red might have similar properties.
Even so, Superboy Prime was defeated after being plunged through Krypton’s red sun – which weakened him, but did not destroy him. Therefore, a red lightsaber which hypothetically had the same properties as a red star, should have a similar effect. For example, it would injure him, but not “cut” him, much less cut through him.
Force of Impact
If Superman were rendered vulnerable by a lightsaber, it would likely create a momentary weakness in that spot, allowing the physical impact to cause damage. However, lightsaber blades, being made of plasma, presumably have a very small mass. Therefore, the force of the impact would be negligible.
In short, hitting Superman with a red lightsaber, is like hitting a normal human with a wet noodle.
answer written by JimM of Yahoo Answers