God Star in Chinese / Japanese...

天 means “heaven” or “sky” in Chinese, Japanese Kanji, and old Korean Hanja.

The context determines if you are talking about heaven or the sky above (often they are the same concept).

When combined with other characters, words like “today” and “tomorrow” are created. While sometimes the character for “sun” is used to mean “day,” often “sky” represents “day” in Asian languages.
Example: 今天 (this sky) = “today,” 明天 (next sky) = “tomorrow” in modern Chinese and Japanese.

In Chinese culture, regardless of which religion, it's almost always assumed that God (and any other deities) live up above the sky. The concept of God living in the sky is likely the reason heaven is associated with this character.
The equation goes something like this: God's domain is the sky, thus, the sky is heaven.

Note: As a single character, this is a little ambiguous, so you might want to choose our Kingdom of Heaven selection instead.

See Also:  Heaven | God | Today | Sun

海王星 is the Japanese Kanji, old Korean Hanja, and Chinese title for the planet Neptune.

海王星 literally means “Sea God Star” (all planets end in the character that also means “star”).