(Similar root we can find in Latin 'dies', which obviously yield 'dia' in Spanish or 'diorno' becoming 'giorno' in Italian after dg-->g sound transformation or 'journée' in French which probably yields the "journey" in English.)
So in few words the terms Ἥλιος or Ἠέλι(ος) in Greek or Illi(ylli)[star] & Dielli(sun) are graphical representatives of a thought/s about a object/s which illu-minate/s.
Lexically and phonetically, now we are dealing again with involvement of an onomatopoeic syllabic supplement- structure: l+vowel, which happens to be a lexeme in Albanian 'le'=re-le-ase~lë-shoj(Al) unlike any other IE language.
Definition of illumination, in every culture is:
This "light supply"(illumination) or the synonym brightening, is called ndriç-im(ndritshim) in Albanian and is acquired : në drite(in light)-->n(ë)dritë)--->ndrit(verb)=gleam=glitten=briten
1 : the action of supplying or brightening with light or the resulting state. 2 : the luminous flux per unit area on an intercepting surface at any given point — called also illuminance.
The involvement of a primitive onomatopoeic structure l-e is done due to the automatic semantic reflexes the palatal "l" carries as an ideo-sound [or as a ideograph(doesn't matter who created)] to imitate the sound or the phenomenon it suggests. The automatic deployment of a following vowel in this minor phonetic structure is inevitable, and its frequent shifting to a different vowel occurs due to deflection or in some rare case preservation and prevention. This change in a phonetic environment, is very normal for the reason expressed above, and certainly for the reason that a language is a vivid organism, which always changes, without loosing the DNA, making it distinct among other languages. While the following vowel might shift to a different one, during declension or word meaning expansion, the phoneme "l", will never le-ave, but always will serve as a vessel to carry that initial abstract meaning, which will not be lost even during the word meaning expansion or contraction.
Using this, is one path, to phonetically/graphically convey the illumination/sun~ star concept. In the case of a "star", Greek (and Latin) is using a different path, to achieve the same objective, coming from a different logic. It's called 'semantics transferability ', from Albanian to create certain dictionary in Greek. The word ἀστήρ (which predates the Latin 'aster'), is an adjacent compound word:
ἀ---> privative preposition = to English un or NOT
στήρ--> is the Albanian meaning sterrë=dark, black
carrying the same meaning with:
1. Shumë i zi; shumë i errët. Natë sterrë. Me leshrat sterrë. U nxi qielli, u bë sterrë.
2. Shumë i ngrysur a i zymtë. U bë sterrë në fytyrë.
3. fig. Që u ka bërë shumë të këqija të tjerëve ose që u dëshiron të keqen, i zi; i përlyer. E ka ndërgjegjen sterrë. E ka shpirtin sterrë.
4. si ndajf. Shumë, fare (për ngjyrën e zezë). Sterrë i zi. I zi sterrë.
which derives again from:
Errësirë. Terri i natës. Iku (u zhduk) nëpër terr. Erdhi për terr erdhi nëpër errësirë; erdhi në të errur, erdhi vonë. Dolëm nga terri.
From erre-m(alb)- ερεμνός, ερεβος, darkness in Greek
1. E mbaj dikë deri vonë natën, e vonoj derisa ta zërë nata. Më erri nata më zuri nata. Mos më err.
2. E bëj dikë të mos shohë fare a të mos shohë mirë për një farë kohe, e verboj.
Ia erri sytë dielli.
3. fig. E bëj të mjerë a fatkeq, nxij. Ia erri jetën.
* I erri sytë vdiq.
s(initial meaning reinforcement sound) +t (vowel-treated: 'të' article) +err(make dark, not-visible)+ ë( noun ending)
The compound word simply means: not-dark, since a star is the only object which illuminates in the sky night darkness and it's not result of any descendance from the presumed PIE root garbage.
This is not an isolated case in Greek, when semantics transferability protocol "borrowing" semantics from Albanian, is enforced. There are many, but one should have a deep understanding in Albanian, to realise that connection between two languages.
The word 'αφρός' seems to have no connection with the cognate in Albanian :' shkumë'. But, the truth is that it borrows its meaning from the Albanian concept afr-oj=appro-ach(ph---f obeys Grimm's law) . The sea-foam is an object in nature, which "the Greeks", have seen to always reach the coast, coming from a certain distance from the sea.
The word itself is used to name the "Morning Star"--Afro-dita, which roughly can be translated : "The day is approaching" which means the "Dawn is coming close". This post will help, to understand that the truth simply can't be hidden in darkness forever, the sun will bring the light, and it will be Aferdita, to signal it first.