Jupiter turns out to be a cat, though the poem takes a while to say so. It begins on a cold, cloudy night in a garden, where a candle flickers in an old lantern and two people sit at a rusty table talking. The city lights have swallowed the stars, so the sky feels empty. Then Jupiter appears, "the only little star coming to us," and the name suddenly makes sense: the animal stands in for the stars that can't be seen.
The speaker feels deep tenderness and gratitude. The line about "so much relief after years of loneliness" suggests this small creature has brought real comfort. The details are gentle and physical: velvet fur, a crossed-eyed look, a quiet listener who sits through "our weird noises, our fast words." The closing lines admit a bittersweet truth, that Jupiter belongs to someone else. Even so, the mood stays warm and quietly happy, like the candle at the start.