Sun and Calendar · 3 of 9

The Sun's Year

Which stars is the Sun standing in front of tonight?

Where the Sun is among the stars tonight, and the year-long walk along the ecliptic that makes the seasons.

You’ll be able to say which constellation the Sun is in tonight, and how its walk makes the seasons.

12 steps · about 9 min

Before this: Measure the Sky with Your Hand (5 min), Celestial Coordinates (8 min), The Ecliptic (8 min)

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Kept for this guide only, until you change it here — your map settings, and every other guide, stay as they are.

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The marked body is the Sun, this minute: under your feet, as far down as the readout says — the map has taken the ground away. Its tag names the constellation behind it. The line through it is the ecliptic, its track for the year.

A whole year, with the air taken away so the stars stay out at noon. The camera holds the Sun on the flat line of the ecliptic, and its tag names each zodiac constellation it enters: it goes east about 1° a day, all the way round.

Now the other side of the sky. Where the ecliptic crosses the celestial equator, on your meridian, is the March equinox point, in faint Pisces. Find it by following the east side of the Great Square of Pegasus on past Algenib. The Sun reaches it about 20 March, crossing the equator heading north.

These stars are up at midnight because the Sun is on the far side of the sky, under your feet. As it moves east, each star crosses your meridian 3 min 56 s earlier a night: two hours a month, west. By late March the Square is lost in the Sun's glare.

Read the equinox point's altitude on your meridian: 90° minus your latitude, north or south. That is the noon Sun's height at either equinox. The celestial equator is half above every horizon, so equinox days last about twelve hours everywhere.

Low in the east-north-east is the top of the ecliptic, where the Sun stands about 21 June. Add its 23.44° to the equinox height for its noon height that day (in the tropics, past 90°: take it from 180°). Most of its daily circle is then above your horizon: your longest day.

Follow the ecliptic down into the west-south-west, to its bottom, in Sagittarius. The Sun is there about 21 December: take 23.44° off the equinox height for its noon height, your shortest day. Across the equator the solstices swap.

Those noons, watched, a day at a time for a year. The Sun climbs to June's height and sinks to December's: its height is the season. The shape it leaves is the analemma.

Now pull the figure-8 apart. Each noon keeps its height and moves along to its date, and the loop opens into a wave: June's top, December's bottom, and two tops in the tropics, where the Sun passes overhead twice. The season, for your own sky.

Why height is the season: a high Sun shines straight down and stays up longer. Distance isn't it: Earth is closest to the Sun about 3 January, in northern winter.

Back to this night's Sun, north at the top. Above the celestial equator, northern days are the longer ones; below it, southern. It crosses twice a year, and strays at most 23.44°. Outside, note where the Sun sets against a rooftop: in a month it will have moved.

The equinox point again, on your meridian. At the next equinox, a noon shadow gives your latitude.

The Sun goes east about 1° a day
Equinox noon: 90° minus your latitude
Solstices add or take 23.44°

The Sun's Year

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