Translation:There are many asteroids in the solar system.
No, the Dutch "trema" (two dots over a vowel) does not indicate a shift in the sound of the vowel, like it does with the German umlaut. Instead, it is a diaeresis: it separates the "o" from the "i" in the pronunciation. You can hear it in this sentence, as-ter-o-i-den, five syllables. Without the dots on the ï, the diphthong "oi" would be pronounced as in the common greeting "hoi". Some more examples:
- Zeeën (pronounced "zay-en") - Seas
- Coöperatie ("Co-op-uh-rah-tsy") - Cooperative
- Diëresis ("Di-er-e-sis") - Diaeresis (i.e., this phenomenon!)
A shame that the spelling for zoëven has changed to zo-even. It used to be my favourite one. :)
- zoeven = moving fast (if somebody passes you it makes the sound zoef, e.g. Roadrunner at full speed, or a car driving the folds out of your trousers if you stand next to the road) ;)
- zo-even = just (a minute ago)
In Dutch zon, maan and aarde are not capitalised. So in line with that it doesn't make sense to use a capital letter for zonnestelsel.
Also according to Van Dale, zonnestelsel can refer to any planetary system. If you follow that definition it's not even clear what system is meant (just a noun, non a proper noun).