What the fuck is this crazy shit.

Modern science.

Gold on Earth came from colliding stars?

All elements were produced by stars (except for hydrogen, helium, and lithium)

Snow detected in young planetary system TW Hydrae? We can detect snow in this shit now?

We can roughly detect elemental composition of a star system / planet by the way a photons wavelength is changed by interacting with a planetary atmosphere.

ALMA may help solve mystery of missing massive galaxies? We're losing track of galaxies?

Haven't read this story yet, but the "missing galaxies" may just be dark matter (from my understanding).

How can I tell what's going to really be important? Or what's even legit?

You have to know a subject intimately before you can tell what is going to be important. If you are interested in space try and learn about A) the basic and fundamental knowledge that we currently have and B) learn about how we learned that (e.g., who discovered what when? And how did they discovery it? What technology did they use? What theory did they develop? etc.)

As for legitimacy, you have to develop a list of dependable sources. Obviously the top science websites are the top science websites via a process of natural selection (ironic?). So if you see an interesting article on Nature or Science, you should take it more seriously than if you see an article discussed on PhysOrg. Not saying PhysOrg is bad... but they aren't giving you proper context and tend to sensationalize new science news. They are still worth reading... but just make sure to take any statement that says "first" or "breakthrough" with a grain of salt.