At last, the final instalment of my series of posts about words relating to perihelion. In my first post on the subject, I discussed the various technical terms in astronomical use (and some that have simply been invented by Wikipedians). In my second post, I discussed words formed from the prefix peri-, and its opposite, apo-. This time around I’m going to talk about words relating to Greek helios, “sun”.

The element helium takes its name from helios because it was, improbably, discovered in the sun before it was known here on Earth—its presence heralded by an unidentified emission line in the spectrum of solar prominences.

A heliograph is a “sun-writer”—a system of mirrors used to send messages by reflected sunlight. If something resembles a child’s drawing of the sun—a central circle and spreading rays—it is helioid. A heliolator is a sun-worshipper, and heliotherapy is an attempt to treat disease by exposure to sunlight. An animal or plant is heliophilous if it loves sunlight; it may exhibit heliotaxis (moving towards the sun) or heliotropy (turning towards the sun). Something that exhibits heliotropy is a heliotrope—a name once given to plants like sunflowers and marigolds that turn their flowers to follow the sun, but now applied to a family of little purple flowers that were once imagined to turn in this way. (Which is why the colour heliotrope is a shade of purple, and not a cheery sunflower- or marigold-yellow.)

The opposite of heliophilous is heliophobic (“sun-fearing”), heliofugal (“sun-fleeing”) or apheliotropic (“moving away from the sun”); the last of which employs our old friend, previously discussed, the prefix apo-. A leaf is paraheliotropic if it turns itself edge-on to overly bright sunlight, so as to avoid burning; and a lizard is diaheliotropic if it turns its long axis transverse to the sunlight, so as to present a large surface area in order to warm quickly on a chilly morning.

I’ve written in the past about parhelia (“beside-suns”)—the patches of bright rainbow light that can appear on either side of the sun, which are also known as sun-dogs. An anthelion is a patch of back-scattered sunlight directly opposite the sun—it’s responsible for the glory that is sometimes seen surrounding aeroplane shadows, or the shadows of mountaineers. And paranthelia are a kind of sun-dog to the anthelion—patches of vague brightness caused by multiple reflections within hexagonal ice crystals either side of the antisolar point. (Although anthelion is formed from the prefix ant- combined with helion, it’s pronunciation gives it a central soft “th” sound: ænˈθiːlɪən.)

And by slipping in the word anti-solar, “opposite the sun”, I’ve made my segue to Latin—sol is the Latin word for “sun”, and solar pertains to the sun. As you’ll know if you’ve read Andy Weir’s book The Martian (or seen the film), sol is the technical term for a Martian day, which is forty minutes longer than its Earth equivalent. The actors in Ridley Scott’s film seemed to be a little uncertain about how to pronounce it—it’s sɒl, with a short vowel that rhymes with doll, not dole. The word has shaken off its Latin origins, and with them its Latin pronunciation. If something resembles the sun in its brilliance (literal or metaphorical) it is soliform; and a solarium is a place you go to enjoy the sun.

The word solstice comes from Latin solstitium, “sun standstill”—the times twice a year, when the sun stops moving towards higher latitudes and starts drifting back towards the equator. A summer solstice produces the longest day and shortest night in one hemisphere of the Earth, but it is simultaneously a winter solstice for the opposite hemisphere, bringing the longest night and shortest day. So unless the context is geographically specific, it’s better to talk about the June solstice and the December solstice. At best talk of “the” summer solstice creates potential confusion; at worst, it causes offence to folk in the southern hemisphere who are justifiably tired of “north-centric” usages.

Something you can hold between yourself and the sun, to get a little shade, is a parasol. An oriental parasol, made of bamboo and oiled paper, used to be called a kittisol, from the Portuguese and Spanish quitasol, “warding off the sun”. And the idea of warding off the sun is implicit in the English word umbrella, too—from the Italian ombrella, “little shadow”. The French at least have a name that matches function—French umbrellas are parapluies, “against the rain”.

Something that follows the sun is solisequious. That gives us the Latin equivalent of Greek heliotrope—solsequium or solsequy, old names for the marigold. French tournesol, “turn-sun”, gives us the English turnsole, an old word for both the heliotrope plant and a kind of purple dye. And Italian girasole (“turn-sun”, again) is the origin of girasol, an old name for the sunflower.

The North American sunflower Helianthus tuberosus was imported to Italy in the seventeenth century, primarily as a root vegetable. Its tubers were found to taste like artichoke, so the Italians called it girasole articiocco “sunflower artichoke”. English speakers imported the vegetable, but misheard the name. And so the girasole articiocco became the Jerusalem artichoke.