1.
first-magnitude star
In astronomy, a star of apparent magnitude 1 — one of the brightest stars visible in the night sky. The magnitude system divides visible stars into six classes, with 一等星 the brightest category regularly taught in schools.
シリウスは一等星だ。
Sirius is a first-magnitude star.
夜空に一等星がいくつか輝いている。
Several first-magnitude stars are shining in the night sky.
オリオン座には一等星がふたつあり、冬の夜空でとても目立つ。
The constellation Orion has two first-magnitude stars, making it very prominent in the winter night sky.
Compound of 一等 ('first class; first rank') and 星 ('star'). The magnitude classification originated with the ancient Greek astronomer Hipparchus and is now part of the standard Japanese elementary-school and middle-school science curriculum.
USAGE:
- Typically used in everyday speech, educational materials, and popular astronomy. Professional astronomers use precise decimal magnitudes instead.
- Worldwide there are about 21 stars classified as 一等星. Well-known examples include シリウス (Sirius), ベガ (Vega), アルタイル (Altair), アンタレス (Antares), and ベテルギウス (Betelgeuse).
- Smaller numbers (first class) indicate brighter stars; larger numbers (sixth class) indicate the faintest stars visible to the naked eye.
COMMON COLLOCATIONS:
- 一等星が輝く: a first-magnitude star shines
- 一等星を見つける: to spot a first-magnitude star
- 一等星クラス: first-magnitude class (rare)
- 冬の大三角: the Winter Triangle — formed by three first-magnitude stars
RELATED TERMS:
- 二等星: second-magnitude star — the next category down.
- 六等星: sixth-magnitude star — the faintest category visible to the naked eye.
- 等級: magnitude (astronomical) — the general technical term.
- 恒星: fixed star — the general astronomical term for a star, as opposed to a planet.