The Transit of Earendil

[Lalwendë]

Getting the puns out of the way first, it's not about Eomer going in a van...

This week we might, if we are lucky, get to see the final pass of the Transit of Venus before the next one in 2117. I've been reading about it this afternoon, and soon got onto thinking about whether Tolkien used the phenomenon in his work (eclipses are explained).

Now in Tolkien's works, Venus is commonly held to be represented by the 'star' Earendil, which so the story goes, is the man Earendil, traversing the heavens with a silmaril bound to his brow. I was trying to find out of there was any instance of the Transit of Venus in Tolkien's work, and came across this odd passage so I'm after thoughts:

On those journeys Elwing did not go, for she might not endure the cold and the pathless voids, and she loved rather the earth and the sweet winds that blow on sea and hill. Therefore there was built for her a white tower northward upon the borders of the Sundering Seas; and thither at times all the sea-birds of the earth repaired. And it is said that Elwing learned the tongues of birds, who herself had once worn their shape; and they taught her the craft of flight, and her wings were of white and silver-grey. And at times, when Earendil returning drew near again to Arda, she would fly to meet him, even as she had flown long ago, when she was rescued from the sea. Then the far-sighted among the Elves that dwelt in the Lonely Isle would see her like a white bird, shining, rose-stained in the sunset, as she soared in joy to greet the coming of Vingilot to haven.

Elwing does not go with Earendil, she doesn't even always join him in the skies. But sometimes she does. I think this isn't the Transit of Venus/Earendil, as the description is totally out. But what might it equate to in astronomy? If anything?

the far-sighted among the Elves that dwelt in the Lonely Isle would see her like a white bird, shining, rose-stained in the sunset, as she soared in joy to greet the coming of Vingilot to haven