Stupid Impact

I watched what is perhaps one of the most stupid science fiction films of all time last night. It was on commercial television, so I suppose I'm really just asking for it.
It was called Impact. I don't care if it is just low budget and made for telly. There is no excuse for plain stupid science mistakes. The main premise of the film is that some super dense asteroid hits the moon, and lodges inside it, making the moon weigh twice as much as the Earth. This asteroid was later shown to be a piece of a brown dwarf. Seriously, there are so many problems with this it is in the same realm as Space 1999, only this was made in 2008! Complete and utter bullshit.
Most obviously to me, anything that weighs around twice as much as Earth and is the size of an asteroid, hitting the moon is just going to punch straight through like it's made of cheese. Conservation of momentum isn't going to see this chunk of superdense rock travelling at interstellar speed slow down anytime soon hitting something one twelfth as massive, especially when it's so much smaller than its target. Bullet through cheese.
Secondly, a brown dwarf is something half way between Jupiter and a star. It's not even a star. I think they probably meant a white dwarf. At least it has a super dense core, and could at a stretch be responsible for the thing in this film. This shit reminds me of Jennifer Anniston in a hair product advert saying "Here comes the science!". Hey, Writer, you suck!
The film progresses from here downhill with random gravitational fluctuations, "like electrical storms", where gravity is practically reversed on the Earth's surface in selected small areas. That's just plain crap. I can't be bothered going on any more. Of course it ends with them trying to blow up the moon, *sigh*, splitting it in half, allowing the super dense asteroid to escape to the Sun, and the two moon halves magically going back into a proper orbit. Oh yeah, I didn't tell you about the gross abuse of orbital mechanics in the film either. Watch it if you want.