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2026.10.22 17:35
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Tonight's Sky
40 CONSTELLATIONS
constellation

Cepheus

세페우스자리
The pentagonal king · The King
Circumpolar · low in the north at night in May
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Science
The science

Cepheus is shaped like a five-sided "house" topped with a steep roof, a circumpolar constellation that wheels near the North Star all year round. Its Delta star (Delta Cephei) is a star that changed all of astronomy. It is a "pulsating variable" whose brightness rises and falls in a regular cycle of 5.4 days, and when Henrietta Leavitt discovered early in the 20th century the law that "the longer such a star's cycle, the truly brighter it is," Cepheids became the "standard candles" for measuring distances to galaxies. It was thanks to these very Cepheid variables that Hubble proved Andromeda to be another galaxy beyond our own Milky Way.

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Mythology
The myth

Cepheus was the king of ancient Ethiopia, husband of Queen Cassiopeia and father of Princess Andromeda. When the queen's boast that her daughter's beauty outshone the sea nymphs brought a sea monster's threat upon the kingdom, an oracle made the cruel demand that Andromeda be offered as a sacrifice. The king who loved his daughter fell into despair, but to save his kingdom he had at last to bind her to a seaside rock. Later, when the hero Perseus rescued Andromeda, Cepheus and his whole family became constellations set side by side in the autumn sky.

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Stars
Main stars (equatorial)
AlderaminRA 21.31h · Dec 62.6° · m2.5
AlfirkRA 21.48h · Dec 70.6° · m3.2
ErraiRA 23.66h · Dec 77.6° · m3.2
IotaRA 22.83h · Dec 66.2° · m3.5
ZetaRA 22.12h · Dec 58.2° · m3.4
DeltaRA 22.49h · Dec 58.4° · m4.1
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Созвездия над вами прямо сейчас

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Ночное небо в реальном времени

Карта созвездий ночного неба в реальном времени

Какие созвездия сейчас у вас над головой, меняется от мгновения к мгновению — в зависимости от времени, даты и вашего местоположения. Пока Земля вращается, звёзды восходят на востоке и заходят на западе; пока Земля обращается вокруг Солнца, видимые созвездия меняются с временами года. Byulgil вычисляет это реальное небо по астрономическим данным J2000.0 и рисует созвездия, видимые из вашего местоположения прямо сейчас, в виде живой карты и в режиме AR. Ничего не нужно устанавливать — просто откройте браузер и посмотрите на сегодняшнее небо.

Созвездия по временам года

Нажмите, чтобы увидеть, созвездия какого сезона видны сегодня ночью.

Constellation Stories

40 историй о созвездиях

Tap a constellation in the sky above to fly to it. Each one comes with the science modern astronomy has uncovered, alongside the myths people have written into those stars.

Solar System

The Solar System

The neighbors of our Sun, wandering among the stars. Meet all nine worlds — from Mercury to Neptune, and on to Pluto — in pictures and stories.

Galaxies

Beyond our own Milky Way lie countless island universes. Tap a galaxy to see its shape and what it looks like.

Observatories near you

Observatories Near You

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What is Byulgil?

Byulgil is a stargazing web app that computes the real night sky for your location, anywhere in the world, in real time. Byulgil means "Star Loads", in Korean. Use your current location (GPS) or pick a major city — Seoul, Tokyo, New York, Sydney — to see the sky exactly as it appears there, right now. Star positions come from real J2000.0 equatorial coordinates, converted to horizontal coordinates for your time and place. On mobile, AR mode lets you point your phone at the sky to overlay the constellations in that direction.