When is the best time to observe Ain?

Ain is best observed from October through December, with peak visibility during November when it transits around midnight in the Northern Hemisphere.

Where is Ain located in the sky?

Ain lies in the constellation おうし at right ascension 04h 29m and declination +19° 11′.

What telescope do I need to split Ain?

Splitting Ain requires an aperture of roughly 60 mm or larger — the components are separated by about 190.4″ at magnitudes near 3.5. The companion is about 7.1 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Ain — おうしの二重星

HIP 20889; Epsilon Tauri; 74 Tauri

等級 3.5^m DoubleStar おうし (Tau) 可視 1 Exoplanet

星図 + リスト + 計画

Ainについて

説明

Ain, Epsilon Tauri, is a K-giant of spectral class G9.5 III about 147 light-years away. It is a member of the Hyades open cluster and became famous in 2007 as the first Hyades star confirmed to host an exoplanet — Ain b, a super-Jupiter of at least 7.6 Jupiter masses in a 1.6-year orbit. Ain's magnitude is 3.53 and its color is a warm pale orange.

観測のコツ

Ain marks the northern eye of the Taurus bull, above the V of the Hyades. In any small binoculars it appears as a warm yellow-orange point surrounded by dozens of fainter Hyades members. Ain is one of the "bull's eyes," with Aldebaran marking the southern eye. Best observed November through March.

歴史

The name Ain is Arabic for "eye," specifically designating the bull's northern eye. The pairing of Aldebaran ("the follower") and Ain ("the eye") in Taurus dates to pre-Islamic Arabic astronomy. The IAU adopted both names in 2016.

豆知識

Ain's planet was the first exoplanet discovered around a Hyades member — a milestone because the Hyades is the closest well-studied open cluster, allowing direct comparison of planetary-system outcomes in a co-evolving population of stars. The 625-million-year-old age of the Hyades means Ain b is a "young Jupiter," useful for studying how giant planets evolve over cosmic time.

観測

1物理的性質

等級 3.53

スペクトル型 G9.5III CN0.5 巨星

星の色橙 (B-V 1.01)

距離 147 ly

2位置と識別子

RA 04h 28m 37.0s

Dec +19° 10' 49.0"

星座おうし (Tau)

HR 1409

HIP 20889

HD 28305

SAO 93954

Bayer Epsilon

Flamsteed 74 Tau

SIMBAD Wikipedia

3分離しやすさ

主星 3.5 mag 伴星 10.6 mag 離角 190.4″

サインインし、機材と既定の場所を設定するとパーソナライズ行が表示されます。

望遠鏡	ボートル3	ボートル4	ボートル5
80 mm 屈折 80mm 屈折	普通	困難+	困難
150 mm ニュートン 150mm ニュートン	容易	普通+	普通
Celestron C8 (203 mm SCT) C8 203mm	容易	容易	普通+