Opening the sky
The brightest star
Sirius is two stars.
Sirius is the brightest star in the night sky, 8.6 light years away in Canis Major, the Great Dog. You can find it by following the three stars of Orion's belt down and to the left. It is about twice the mass of the Sun and gives out about 25 times as much light.
In 1844 Friedrich Bessel noticed that Sirius wobbles as it moves across the sky, and argued that an unseen companion was pulling on it. In 1862 the telescope maker Alvan Graham Clark, testing a new lens, saw it: a faint point right beside Sirius. We now know Sirius B is a white dwarf, the burnt-out core of a star, with about the mass of the Sun packed into a ball the size of Earth. The two circle each other every 50 years.
Its name comes from the Greek Seirios, often translated as glowing or scorching. Egyptians watched for its first dawn rising to mark the coming of the Nile flood, and Arab astronomers called it al-Shiʿrā. Click Sirius in the sky above to see the pair on their real orbit.
Sirrius, the studio that made this page, takes its name from the star, with one extra r.
Colophon
How we built this
The sky is drawn from real catalogs: 8,920 stars down to the faintest you can see by eye, each placed by its measured position and coloured by its temperature. The Sun's place on your birthday is computed, not looked up in a table, so the constellation you see is the one the Sun really stood in front of, Ophiuchus included.
All 88 constellations are drawn, with the stick figures most modern star atlases use. These join only the brighter stars, so some are spare: Canis Minor is a single line. Every line ends on a real star, and where a figure reaches into its neighbour, as the serpent of Serpens does through the hands of Ophiuchus, that is how the figures have always been drawn.
The stories come from published sources, each one linked beside the text. The guide is a language model that answers only from those cited notes, and it will not read your horoscope. Your birth date never leaves your browser.
It took one week, using Next.js, three.js and Astronomy Engine, with Claude for the guide.
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Get in touchCredits
- HYG star database v4.1David Nash (astronexus) · CC BY-SA 4.0
- Constellation lines, names and Milky Way outlined3-celestial, Olaf Frohn · BSD 3-Clause
- Sun position and constellation boundariesAstronomy Engine, Don Cross · MIT
- Orbit of Sirius BBond et al. 2017, The Astrophysical Journal 840:70 · cited
- Earth surface map, Blue MarbleNASA Visible Earth · Public domain
- Planet and Moon maps: Cassini, MESSENGER, Magellan, LRO, Black MarbleNASA, JPL, NASA 3D Resources · Public domain
- Saturn ring dimensionsNASA Rings Fact Sheet · Public domain
- Planet factsNASA Planetary Fact Sheet · Public domain
- 3D renderingthree.js · MIT
Every fact here comes from a cited source. If you find one that is wrong, write to hello@sirrius.net with the right value and where it comes from; we check it against the source and correct it for everyone. Star data derived from HYG is shared under CC BY-SA 4.0. The sources for each tradition's story are linked in its card. Traditions are presented as their own sources tell them; no part of this page is astrology.