Experimental plasma physicist Dr. Mike Zarnstorff has at least one thing in common with Darth Vader: his opinion of the ability to destroy a planet.
Zarnstorff, the Deputy Director for Research at the Princeton Plasma Physics Laboratory, doesn't trump planet-decimation with a mystical energy field, though. He's going for something a bit stranger, and a lot more powerful.
A Black Hole.
In an interview with Life's Little Mysteries, Zarnstorff explored some of the difficulties with how you'd go about destroying something as massive as the Sun, to distill us down to something that might work.
First, the Sun is so big and so hot that it would be impossible to disrupt it simply by throwing something into it. You could take every other speck of matter in the solar system and throw it into the Sun and it wouldn't make any difference. Even setting off an explosion wouldn't do anything. Sending every nuclear weapon on Earth into the Sun at once would have no effect at all.
Another idea he proposed was to "poison" the nuclear fusion in the Sun, however he doesn't see that method as being very plausible. The nuclear fusion reactions in the Sun's core started off turning hydrogen atoms into helium atoms. When there is only helium atoms left in the core, the Sun will balloon into a Red Giant and its core will be crushed by gravity until helium atoms begin fusing together into heavier elements. This continues again and again as the core uses up its current fusion fuel and is crushed further, going through carbon, neon, oxygen, silicon, and then finally iron. When the core consists only of iron, even the massive gravity of the Sun will not be able to crush that iron core enough to fuse the iron atoms together, and the core will completely collapse. The Sun will then go nova, blowing off its outer layers until all that is left over is a white dwarf star. This process occurs over billions of years, though, and there's very little chance of human beings effecting the process.
Evaporating the star is another possible way. The solar wind constantly draws matter off of the Sun, but the overall effect is tiny. However, if you were to find a way to make that wind blow harder and significantly increase the loss of mass, like a colossal magnetic field generator, the sun would eventually shed all its outer layers. By eventually, though, he means tens of millions of years, so it's not exactly up to 'Doomsday Weapon' standards.
So, finally we get to the one that he thinks is, if not very likely, at least plausible.
"A black hole could suck in all the mass of the Sun," Zarnstorff told Life's Little Mysteries.
If you could create the black hole inside the Sun, it wouldn't matter what size of black hole you created. It would simply feed on the Sun and grow exponentially, becoming more massive and feeding faster until the Sun was completely consumed.
However, if you wanted to launch it from Earth, you would have to plan the size of the black hole very carefully, due to a phenomena called Hawking Radiation - named after Professor Stephen Hawking, author of A Brief History of Time, who provided the first theoretical argument for the phenomena. Hawking radiation is similar to the black body radiation given off by the Sun, but specifically describes the radiation emitted by black holes. If a black hole has no source of matter and energy, it quickly evaporates due to Hawking radiation and is gone. For example, the tiny black holes created in The Large Hadron Collider, at CERN, near Geneva, Switzerland, evaporate in just billionths of a billionth of a second - so quickly that you can hardly have considered them to have existed at all.
Zarnstorff suggests that a black hole about a millimetre in diameter, with a mass roughly that of the moon, might be enough to do the job, but thankfully creating something like that is still far beyond our technology.