Ashlesha: the coil, the gist

Ashlesha: the coil

The ninth of the moon's twenty-seven stations is a small knot of five faint stars that make the head of the longest constellation in the sky, and its name is the ordinary word for an embrace.

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

Two of those five stars carry old Arabic names meaning the serpent's tongue and the serpent's nostril. Somebody had drawn the face before anybody got round to naming the parts of it.

The essay follows one line. It starts at the westernmost of five faint stars in the head of Hydra, the water snake, and traces the shape star by star.

First comes delta Hydrae, a white star spinning so fast that it bulges at the equator. Arabic lists called it the serpent's tongue. Two and a half degrees south is sigma Hydrae, an orange giant whose name, Minchir, is worn down from the Arabic for the serpent's nostril.

A degree east is eta Hydrae, which looks like the other two and is nothing like them: a blue star seven times the mass of the sun, putting out more than two thousand times the sun's light, and only thirty million years old. It looks faint because it is far away.

Then the brightest of the five, epsilon Hydrae. This is the star the station is measured from, and in 2018 the International Astronomical Union officially named it Ashlesha. Last comes rho Hydrae, close beside it.

Together the five make a shape about three degrees each way, roughly six full moons across. The two ends do not meet. It is a loop that does not close, which is what a coil is.

The line then leaves the station, passes a star brighter than any in the head that the old lists left out, and runs on into a constellation so long that its head and tail are about seven hours of sky apart.

To find it, use Procyon: it rises at the same point on the horizon about an hour earlier. The sun sits in this patch of sky in early August, so the station is invisible then; it returns before dawn in late September, and belongs to the evening from December onwards.

The name is built on a root meaning to cling or fold around. It means an embrace. The presiding figures are the nagas, serpent beings connected with water and rain. The essay ends on the double meaning: an embrace and a grip are the same act, and which one it is depends on whether the other person can leave.

Words decoded

nakshatra (नक्षत्र): one of twenty-seven slices of sky, one for roughly each night the moon takes to go round
Ashlesha (आश्लेषा): the ninth slice; the word means an embrace, a clasping, a folding around
yogatara (योगतारा): the "junction star", the one fixed star used to pin a nakshatra to the real sky
magnitude: the brightness scale astronomers use; it runs backwards, so a bigger number means a fainter star, and about 6 is the faintest a good eye can manage
light year: how far light travels in a year; a star 350 light years away is seen as it was 350 years ago
Hydra: the Latin name of the water snake, the largest constellation in the sky
ecliptic: the line the sun follows through the stars over a year; the moon stays close to it
naga (नाग): a race of serpent beings in Indian tradition, connected with rivers, wells, rain and buried treasure
Nag Panchami: the day kept for them, the fifth of the bright fortnight of the month of Shravana, falling in July or August

Why anyone should careMost writing about this station starts with a personality description. This one starts with five faint stars you can actually go and find, and it turns out the shape they make explains the name better than any handbook does. Knowing where a thing is in the sky changes how much authority you hand to anyone who talks about it.

Read it properly, 8 min Ashlesha: the coil