When is the best time to observe Tau Eridani?

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

Where is Tau Eridani located in the sky?

Tau Eridani lies in the constellation 에리다누스 at right ascension 03h 20m and declination -21° 45′.

What telescope do I need to split Tau Eridani?

Splitting Tau Eridani requires an aperture of roughly 80 mm or larger — the components are separated by about 5.8″ at magnitudes near 3.7. The companion is about 5.8 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Tau Eridani — 에리다누스의 이중성

HIP 15474; Tau4 Eridani; 16 Eridani

등급 3.6–3.7^m DoubleStar 에리다누스 (Eri) 관측 가능

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Tau Eri 소개

설명

Tau Eridani is a red giant of spectral class M3 III-IIIa Ca-1 about 304 light-years away. It shines at magnitude 3.69 and is a semiregular variable, with brightness variations of about 0.1 magnitudes on a 30-day period. Tau Eri is a mature asymptotic-giant-branch star approaching the end of its life.

관측 팁

Tau Eri sits in the northern part of Eridanus. Its deep orange-red color is striking in binoculars. Long-term amateur monitoring can track the variability, though the amplitude is modest. Best observed October through February.

역사

Tau Eri retains its Bayer designation in current IAU catalogs.

재미있는 사실

Tau Eri's M3 spectrum shows strong molecular absorption bands from titanium oxide, calcium hydride, and other molecules — signatures of the cool outer envelope of a red giant. Its mass-loss rate is high enough that the star is shedding material into a growing circumstellar shell.

관측

1물리적 특성

등급 3.69

범위 3.57 - 3.78

주기 23.8 일

변광성 유형 Semi-Regular Variable (Short Period)

분광형 M3III-IIIa Ca-1 거성

항성 색상 빨강 (B-V 1.62)

거리 304 ly

2위치 & 식별자

RA 03h 19m 31.0s

Dec -21° 45' 28.0"

별자리 에리다누스 (Eri)

HR 1003

HIP 15474

HD 20720

SAO 168460

Bayer Tau4

Flamsteed 16 Eri

Variable ID Tau4 Eri

Double Cat 2472

SIMBAD Wikipedia

3분리 난이도

주성 3.7 mag 반성 9.5 mag 이각 5.8″

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망원경	보틀 3	보틀 4	보틀 5
80 mm 굴절 80mm 굴절	극난+	극난+	극난+
150 mm 뉴턴 150mm 뉴턴	어려움+	어려움+	어려움+
Celestron C8 (203 mm SCT) C8 203mm	보통	보통	보통