Earth vs. earth

I'm with you on this one, Heimhenge.   Being an astronomy geek, I tend to notice that, too.   And yes, it does seem to be happening more.   My guess?   Lack of proper science education.  

This is totally off the cuff and I have absolutely no expertise in astronomy. In fact I feel like a beginning student lecturing the teachers when I try to answer Heimhenge and Jackie, but I am writing this out so that others can verify it or shoot it down.   Here we go.

It seems you are using words that can be used both as proper nouns and generic nouns.   I don't know how they used it in the articles you read.   It is my understanding that almost every star is the sun of the solar system they inhabit, therefore there are many suns.   This is a generic noun.   I believe our sun's proper name is Sol, although rarely used, but often I think people use "The Sun" as a proper name.

Moon is also a generic noun when you are talking about the billions of moons circling the billions of planets in the universe.   All of the moons close to us have their own proper names.   Our moon's proper name is Luna but, like the Sun, I think people use "The Moon" as a proper name.

So I believe that the words sun and moon are capitalized, or not, depending on whether you are using them as proper names or generic nouns.

You're correct, Dick.   But all too often, I see the generic forms when the proper should be used.   Now I'm not sure if it's a lack of proper science education, or proper English education.   Perhaps both.

In non-scientific literature, low case is more common than up for sun, moon, earth:
He saw the sun low in the sky.
The moon emerges from behind the clouds.
He saw Venus, Jupiter and moon/the moon all high in the sky.
The stars look down on the sleeping earth.

Writing about our solar system, low case is still ok for sun,moon,earth, but no mixed cases:
Third from the Sun is the Earth.
Third from the sun is the earth.
The ancients identified 5 peripatetic objects: Mercury, Venus, Mars, Jupiter and Saturn, besides Sun and Moon.
The ancients identified 5 peripatetic objects: Mercury, Venus, Mars, Jupiter and Saturn, besides sun and moon.
The ancients identified 5 peripatetic objects: Mercury, Venus, Mars, Jupiter and Saturn, besides the Sun and the Moon.
The ancients identified 5 peripatetic objects: Mercury, Venus, Mars, Jupiter and Saturn, besides the sun and the moon.

Writing about space, suns and moons are low-cased; all named objects upper-cased:
Ours is one of at least 100 billion suns in the Milky Way.
Our Sun is one of at least 100 billion stars in the Milky Way.
The Moon is larger than Europa, the smallest of Jupiter's moons.