a story of four stars +

The piece

a story of four stars is played from a live score: a map of the northern sky that turns slowly on the screen, drawn from the Hipparcos catalogue with each star sized by its true brightness. A vertical line — the playhead — stands across the sky. Whenever a star touches it, the star sounds.

Every star keeps its own fixed pitch, set by its distance from the pole, and its loudness follows its brightness. Each constellation has its own family of bell-like voices in the electronics, so the turning of the sky becomes a slow music of recurring collisions: stars returning to the line, meeting it again, never quite in the same order. As they move, the brightest stars leave fine coloured trails, and the score gradually draws its own history in loops and circles.

Four stars

The score is a guided tour. It begins with Polaris, the north star — which, looked at closely, is not quite on the pole at all. From there the view travels to Vega, Deneb and Altair, each introduced by a short text and held at the centre while its constellation wheels around it, and then to the Summer Triangle the three make together: not a constellation, but a shape that exists only from where we stand. Altair is seventeen light years away, Vega twenty-five, and Deneb perhaps a hundred times further; their light, set out in very different centuries, arrives together tonight.

The weaver and the cowherd

In the Chinese legend retold at the Qixi festival, Vega is Zhinü, the weaver girl of heaven, and Altair is Niulang, the cowherd she married against heaven's will. The Queen Mother of the West drew the Milky Way between them with her hairpin, a river of stars they cannot cross — except on the seventh night of the seventh month, when magpies form a bridge. The old star names carry the story's sounds: Altair is Hégǔ, the River Drum; Deneb sits in Tiānjīn, the Heavenly Ford; and a Han-dynasty poem hears the weaver at work in the clack of her loom and shuttle.

A wandering pole

The sky's centre is not fixed. The Earth spins like a slightly wobbling top, and over about 25,800 years its axis traces a wide circle across the stars. The pole is drifting towards Polaris now; it will pass Gamma and then Alpha Cephei, come close to Deneb around the year 10,000, and reach Vega around the year 13,800, when Vega — one full turn of the wobble after it last held the place, around 12,000 BCE — will again be our pole star.

In the final part of the score this journey is compressed into three minutes. A small red marker leaves the pole and travels the real path of precession, and the whole sky turns around it as it goes, until Vega stands at the still centre and every trail draws a circle around her. Then the view opens onto the entire sky, every constellation at once.

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