The family of the sun-god Helios features many minor goddesses of sun and light. Helios is the main god of the sun; his name, and his resemblance to many Indo-European sun-gods and goddesses puts that out of doubt, but it is interesting how solar females cluster around him.
Some of these goddesses may well have had their own solar cults long ago, but it’s impossible to verify now. Two of them were his mother and aunt, the other was his daughter. (Helios’s lineage also includes the witches Circe and Medea, as well as Hecate, a grand-daughter in some versions of her family tree.)
Theia: one of the Titans, the gods who ruled before Zeus and his siblings overthrew Cronos and became the Olympians. She was probably a primal goddess of light. Her husband was the Titan Hyperion, and their children were Helios, Selene and Eos, or the sun, moon and dawn. (The ancient Greeks believed the eye sent forth beams of light that struck the object and made it visible. Thus Theia “sent forth” her bright children, and her name may be a pun, since thea also meant “sight”.)
Her name is the feminine form of Theos, “God”, and could be translated as “Divine” or “Goddess”. (See the Gaulish Divona.) The Homeric Hymn to Helios calls her “mild-eyed Euryphaessa, the far-shining one”. (The name means the same, “wide-shining”.) Pindar says: “thanks to thee men ascribe to gold a strength exceeding all other powers that are,” (Ismathian Ode 5.1) and Theia supposedly gave gems, silver and gold their brilliant lustre.
Theia personified light, while Hyperion was the Titan version of the sun, and the feminine aspect of Aeither, the bright blue sky. As an oracular goddess, her name was connected to the verb theiazo, to prophecy. Under her title Ikhnaie (The Tracing One) she had a shrine in Phthiotis in Thessaly. (It seems most of the female Titans had oracular shrines.)
Phoebe: another oracular goddess, since she owned the temple at Delphi before giving it to her grandson Apollo. Her name comes from the Greek words phoibos, “bright” or “radiant,” phoibaô “to purify” and phoibazô “to give prophecy”. (One of Apollo’s and Helios’ by-names was Phoibos, the Radiant.) She was married to Kolos, “the Enquirer”, and god of the earth’s axis (especially in Roman mythology).* Their children were Leto, mother of Apollo and Artemis, and Asteria, mother of Hecate.
Helia: came from a much younger generation, since she was one of Helios’ children. She was one of seven daughters, known as the Heliades, according to Hyginus. (Other sources give three.) When Zeus killed their brother Phaethon, they stood so long by the river where he fell, weeping, that the gods turned them into poplar trees that dripped amber. (There is a vague echo of the Scandinavian goddess Freyja, searching for her missing husband, and weeping tears of gold and amber.) The river’s name may come from this event, as Eridanos means “Early Burnt”.
Helia is obviously a female form of Helios, fitting for a sun-god’s daughter, and her six sisters also have names that echo their solar descent: Aethria (Clear Sky), Lampete (Torch, Shining), Aigle (Dazzling Light), Aigiale (Of the Sea Shore), Dioxippe (Horse Driving), and Merope (Face Turned). Pheobe (Bright), and Phaethus (She Who Illuminates). Their mother was Klymene, a sea-nymph and daughter of Ocean.
The sun and the ocean are closely connected in Greek myth, which probably has a lot to do with geography. Helios owns several islands, and he rows himself across the sea each night so he can rise in the east. He also married one sea-nymph and dallied with two more, Rhode and Klytie. (Who pined so after he left her that she turned into the heliotrope, a purple flower that follows the sun.)
* Polos was supposed to be the North Pole, while Hyperion the solar Titan was the Eastern one. The four poles were supposed to hold Heaven and Earth apart.