When is the best time to observe Chamukuy?

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

Where is Chamukuy located in the sky?

Chamukuy lies in the constellation Taurus at right ascension 04h 29m and declination +15° 52′.

What telescope do I need to split Chamukuy?

Splitting Chamukuy requires an aperture of roughly 60 mm or larger — the components are separated by about 336.9″ at magnitudes near 3.4. Larger apertures and steady seeing help resolve the pair cleanly.

Chamukuy — Double Star in Taurus

HIP 20894; Theta2 Tauri; 78 Tauri

Observable Double Star Excellent (63/100)

Sep: 336.9", Companion: mag 3.9

Magnitude 3.4^m DoubleStar Taurus (Tau) Visible

Star Map + List + Plan

About Chamukuy

Description

Chamukuy, Theta2 Tauri, is an A7 III giant star about 150 light-years away — the brightest member of the Hyades open cluster, the nearest prominent open cluster to the Sun. Chamukuy is a spectroscopic binary with a period of 140.7 days and an A7 V companion. The combined magnitude is 3.40. The star is about 2.6 solar masses and lies in the heart of the V-shaped Hyades asterism that forms the face of Taurus the Bull.

Observing Tips

Chamukuy sits at the eye end of the Hyades "V," very near Aldebaran (a foreground star, not actually a Hyades member). In binoculars Chamukuy is unmistakably bright in a field of dozens of Hyades members. The Hyades is the easiest naked-eye open cluster in the entire sky — every star you can count in the V is a Hyades member, about 150 light-years distant and 625 million years old. Best observed November through March.

History

The name Chamukuy is from the Mayan language, meaning "small bird" — a reference to a celestial bird in Mayan astronomy. The IAU adopted the name in 2017 as part of an effort to recognize indigenous American star names.

Fun Facts

Chamukuy is one of the Hyades cluster's few bright binaries, and its spectroscopic orbit provides fundamental mass calibrations for the cluster's stellar population. Aldebaran, which lies along the same line of sight as the Hyades and appears to be one of its members, is actually a much closer foreground star — at 65 light-years, less than half the Hyades distance.

Observe

1Physical Properties

Magnitude 3.40

Range 3.35 - 3.42

Period 1.8 hours

Variable Type Delta Scuti (Low Amplitude)

Spectral Type A7III giant

Star Color Yellow-white (B-V 0.18)

Distance 150 ly

2Position & Identifiers

RA 04h 28m 39.7s

Dec +15° 52' 15.0"

Constellation Taurus (Tau)

HR 1412

HIP 20894

HD 28319

SAO 93957

Bayer Theta2

Flamsteed 78 Tau

Variable ID The2 Tau

SIMBAD Wikipedia

3How easy to split?

Primary 3.4 mag Companion 3.9 mag Separation 336.9″

Telescope	Bortle 3	Bortle 4	Bortle 5
80 mm refractor 80mm refr.	Easy	Easy	Easy
150 mm Newton 150mm Newt.	Easy	Easy	Easy
Celestron C8 (203 mm SCT) C8 203mm	Easy	Easy	Easy

Easy Medium Hard Very hard Impossible

Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs

4Visibility

Set a location in User Settings to see visibility data.

Best season Oct – Dec (peak: Nov)

5Light Curve

6Multiple Star System Quadruple

Components 4 (quadruple)

Component IDs AB

Separation 336.9″

Companion Mag 3.9

Position Angle 347°

Star Colors A: Yellow-white B: Orange

Discoverer STFA 10

Notes

CPM with HR 1411. Close occultation binary, 3.5, 5.8v, sep. 0.005".

Separation over time

Measured 1800 → 2019 (219 y)

Separation drift 340.0" → 336.9" (-3.10")

Rate -0.0142" / y

PA drift 346° → 347° (+1°, +0.005°/y)

Slow change over generations — observable in lifetime comparisons.

Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.