✦ Which star is the Sun near today? Write it a postcard

As the Sun moves around the zodiac it passes real stars, one after another. Umbriel's free Postcard to the Star finds the fixed star the Sun is nearest today, from a catalogue of 277, and shows exactly how far away it is. You write that star one sentence on a postcard with a dated stamp. Over a year your postcards trace the Sun's walk around the sky.

• What you'll needOne sentence; no chart and no account
• What you getToday's nearest fixed star with its constellation, brightness and distance from the Sun in degrees, a postcard for one sentence, and a ring of the year's stars with a postcard at each one you wrote to, printable as one plate
• CostFree, no account required

The Sun spends the year walking a fixed path through the stars. We cannot see them while it passes, because it is daytime, but they are there, and each has a name that is often thousands of years old. Postcard to the Star tells you which one the Sun is beside today.

The card names the star, gives its Bayer letter and constellation, its brightness, and how far it is from the Sun along the zodiac in degrees, along with how far it sits above or below the Sun's path. When the Sun is within a fifth of a degree, the card says it is on it. Some stars carry a line from astrological tradition, written for Umbriel and labelled as such; for the rest the card gives the plain facts and invents nothing.

Then you write the star one sentence, on a postcard with a dated stamp. It can be anything: a question, a thank-you, the weather. It is kept, not posted.

The year object is the walk around the ecliptic: a ring with all 277 stars on it and a postcard at each one you wrote to. A star the Sun passed with no postcard is a small tick on the ring, nothing more. From the second year on, last year's postcard to a star sits beside this year's, so you can read what you said to Regulus a year ago.

A star gets one postcard a year, and writing again changes it. Nothing counts, nothing is owed, and it works for someone who opens it only on Sundays.

Your postcards stay private, on your device, and if you sign in they sync end to end encrypted, the same way the journal does. Nothing is posted.

The Sun's position is the engine's apparent longitude for today, the same calculation the live sky uses. The 277 stars are the engine's own fixed-star catalogue, each moved from its catalogue epoch to today by precession at 50.29 arcseconds a year. The distance on the card is the real difference in ecliptic longitude between the Sun and the star, and the star's distance above or below the Sun's path is its ecliptic latitude, worked from the star's own right ascension and declination. Every star position was cross-checked between two independent catalogues to within 12 arcminutes, so a separation under a fifth of a degree is shown as the Sun being on the star rather than as a number finer than the data supports. The two lines about each star are built from the catalogue itself: its Bayer letter and constellation, its magnitude, where it sits today and how far it is off the Sun's path. A sentence from astrological tradition exists for 37 of the 277, is shown under a label saying it was written for Umbriel, and is left out rather than invented for the other 240. A postcard is filed under its star and its year.