Gen 1:3 And God said, "Let there be light," and there was light.

That light we can assume was either an uncreated light that was temporarily provided from God, even God’s glory that separated the darkness until He put the universe in order. (spiritually speaking, That same light is found in the glory of the gospel)

after the heavens and earth are created (earth being the only heavenly body at the time) The first work of God is the calling light into being by His word. His supernatural power causes the presence of light to manifest to remove the darkness mentioned in the preceding verse,-"and darkness was upon the face of the deep." It was not for other planets but exclusive to the earth, nor is it from the formation of another created thing (like the sun) but from his pronouncing `Light shall be.' His divine command made it take place.

This began the creation narrative.

Isa 48:13 My own hand laid the foundations of the earth, and my right hand spread out the heavens; when I summon them, they all stand up together.”

Isa 55:9 “As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts. V:11 so is my word that goes out from my mouth: It will not return to me empty, but will accomplish what I desire and achieve the purpose for which I sent it.”

God spoke and it took place.

Notice also the light from the stars was there on the 4^th day, the same day they were created. Which would also perplex scientists since these stars would be far away for the light to reach us.

On the third day (Gen. 1:11) Then God said, "Let the earth bring forth grass, the herb that yields seed, and the fruit tree that yields fruit according to its kind, whose seed is in itself, on the earth"; and it was so.

How would the plants be able to live without light? This is why God made this light to divide the day until he made the permanent lights from creation to be there.

Gen 1:14-19 And God said, "Let there be lights in the expanse of the sky to separate the day from the night, and let them serve as signs to mark seasons and days and years, and let them be lights in the expanse of the sky to give light on the earth." And it was so. God made two great lights--the greater light to govern the day and the lesser light to govern the night. He also made the stars. God set them in the expanse of the sky to give light on the earth, to govern the day and the night, and to separate light from darkness. And God saw that it was good. And there was evening, and there was morning--the fourth day.

Revelation tells us that the sun will no longer be needed and God will be the light which we can presume is this same Genesis light that was there before the sun and stars.

Rev 22:5 There will be no more night. They will not need the light of a lamp or the light of the sun, for the Lord God will give them light. And they will reign for ever and ever.