If you understand this and if you understand English articles, you will almost be there. "Almost" because of your accent.
Now back to your tense question.
>which was named after its discovery...
The speaker's mind places the event in the past. He says (you could draw this understanding from the tense alone) that there was a time in the past that followed the day of the discovery (because of the word "after") and witnessed the act of naming it. The name may have been changed or not been changed since then and the discovery may be recognized or not be recognized today by the same name, but all of this commentary of mine is not stated in any way in the original sentence. The original sentence does not deal with what we know/think/believe today. It makes a statement about a past event, free of what we deal with/think about/believe today. You must understand this. It's the #1 key point.
>which has been named after its discovery...
It says it was named later on; it was named sometime/anytime between the time of the discovery and the present. It's not important when the naming occurred. What counts is that today we recognize that the discovery acquired a name one day in the past and that the act of naming so the discovery is what the discovery has experienced. I am using the word "experienced" deliberately, because it conveys the sense of the present perfect tense. You must understand this. It's the #2 key point.