Jyeshtha: the eldest, and the rival of Mars, the gist

Jyeshtha: the eldest, and the rival of Mars

The eighteenth of the moon's twenty-seven stations is marked by Antares, a star so large that light needs most of an hour to cross it, and the essay climbs a ladder of size measurements until it notices that not one of them is actually a size.

This is the short way in. The essay has the working, the sources and the sky.

Light crosses our own sun in about four and a half seconds. To cross Antares it needs the better part of an hour. And nobody can tell you exactly how wide the star is, because it swells and shrinks as it goes, so the honest answer depends on when you asked.

Face south on an evening in the first half of the year and look for a single orange point, fairly low down. One fainter star stands above it and another below. Three fingers held up at the end of a straight arm will cover all three. That short line is the whole station.

The orange one is Antares, a red supergiant: a heavy star near the end of its life that has swollen up and cooled at the surface. Cool surfaces glow red, and that is all the colour means.

The essay walks up a ladder of measurements, each one larger than the last. Three fingers of sky. A faint companion star tucked in beside Antares, found in 1819 because the moon passed in front of them both. The gap between those two stars, which works out to seventeen times the distance from the sun to Neptune. The width of Antares itself, around six hundred and eighty times the sun's radius, though published figures disagree and the star's own pulsing keeps changing the answer.

Then the essay stops and looks at its own list. Not one of those numbers is a size. Every one is a ratio: this thing held up against that thing. There is no unit of bigness. A metre is a stick people agreed on.

That matters for the names, because the station has two and both are comparisons. Antares is Greek for the rival of Mars, which describes an enormous star by borrowing a small planet. The Sanskrit name Jyeshtha means the eldest, and a superlative is a comparison with the other terms left out of the sentence. Nobody is the eldest on their own.

So the essay treats this station as being about rank rather than personality. Being the eldest in a house is not an achievement. You arrived first, and the duties were attached afterwards. That is worth thinking about, and it is not a prediction about anybody.

Words decoded

nakshatra (नक्षत्र): one of twenty-seven slices of sky, one for roughly each night the moon takes to go all the way round
Jyeshtha (ज्येष्ठा): the eighteenth slice. The word means eldest and most senior, and also best or chief
Antares: the bright orange star at the middle of this station, in the constellation the West calls Scorpius, the scorpion
red supergiant: a heavy star that has used up the fuel in its core, swollen enormously and cooled at the surface, which is why it looks orange or red
magnitude: the brightness scale astronomers use. It runs backwards, so a smaller number means a brighter star
light year: the distance light travels in one year
solar radius: the distance from the centre of the sun to its surface, used as a measuring stick for other stars
second of arc: a very small unit of angle in the sky. The full moon is about 1,800 seconds of arc wide
ecliptic: the line the sun appears to follow through the stars over a year. The moon stays close to it, which is why it can pass in front of a few bright stars
occultation: when the moon passes in front of a star and hides it for a while
Indra (इन्द्र): the figure the tradition attaches to this station. In the oldest Indian hymns he is the chief of the gods and the one addressed most often
superlative: the "-est" form of a word: biggest, eldest, best. It means nothing unless there is something else to compare against

Why anyone should careAlmost every impressive number about a star turns out to be a comparison with something else quietly doing the work, and so does the sentence a handbook writes about your character. Proud and senior mean nothing until you ask proud beside whom, and senior to what. Noticing the missing half of a comparison is a useful habit, in the sky and in a family, where the eldest is only the eldest because of who came afterwards.

Read it properly, 8 min Jyeshtha: the eldest, and the rival of Mars