HIP 21619 — Double Star in Taurus

Magnitude 6.5^m DoubleStar Taurus (Tau) Visible

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Observe

1Physical Properties

Magnitude 6.47

Spectral Type F2V:

Distance 155 ly

2Position & Identifiers

RA 04h 38m 29.6s

Dec +26° 56' 24.0"

Constellation Taurus (Tau)

HR 1470

HIP 21619

HD 29364

SAO 76682

Double Cat 3353

3How easy to split?

Primary 6.5 mag Companion 7.2 mag Separation 4.4″

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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

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Best season Oct – Dec (peak: Nov)

5Multiple Star System C: optical

Separation 4.4″

Companion Mag 7.2

Companion Sp F2V

Position Angle 188°

Star Colors A: Yellow-white B: Yellow-white

Discoverer STF 572

Notes

Occultation indicated mag. diff 0.37v, sep. 2.117" (half the visual sep.) and PA 78d in contrast to visual 194d.

Separation over time

Period: 5012.5 y Eccentricity: 0.740 Now: 4.4", PA 188° + 0.03" in 5 years

Apparent separation over time, computed from ORB6 orbital elements. Steep curves indicate fast-changing pairs — catch them while they're splittable.

Eyepiece View

Telescope Eyepiece

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80x Dawes: 1.9″ TFOV: 0.6°

Seeing

Scale Realistic = true angular size

A: 6.5 · B: 7.2 · Sep: 4.4″ · PA: 188° · N up, E right

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″

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6

Size Comparison

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Spectral Classification

9

Hertzsprung-Russell Diagram

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Stellar Lifecycle

11

Blackbody Spectrum

12

Stellar Absorption Spectrum

Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.

13

Stellar Fusion

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14

Light Travel Time Machine

15

Relativistic Travel

Nearby in the Sky

Other targets within a few degrees — pan your scope a little and keep exploring.

Visibility scores assume a 150 mm Newton at Bortle 4.

Colorful double, sep 19.4″

Double Star mag 5.37 3.8° Taurus

Easy double, sep 62.5″

Double Star mag 4.28 4.1° Taurus

Eclipsing binary, period 2.1d

Variable Star mag 5.92 6.3° Taurus

Rich open cluster

Open Cluster mag 6.0 6.5° Taurus

Planetary nebula — try an OIII filter

Planetary Nebula mag 10.0 7.5° Taurus

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