HIP 7751 — Double Star in Eridanus

Observable Double Star Excellent (67/100)

Sep: 11.4", Companion: mag 5.9

Magnitude 5.9^m DoubleStar Eridanus (Eri) Visible

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Observe

1Physical Properties

Magnitude 5.87

Spectral Type K0V

Star Color Orange (B-V 0.90)

Distance 21 ly

2Position & Identifiers

RA 01h 39m 47.4s

Dec -56° 11' 53.0"

Constellation Eridanus (Eri)

HR 486

HIP 7751

HD 10361

3How easy to split?

Primary 5.9 mag Companion 5.9 mag Separation 11.5″

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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 Sep – Nov (peak: Oct)

5Multiple Star System

Separation 11.4″

Companion Mag 5.9

Position Angle 185°

Star Colors A: Orange B: Orange

Notes

Binary with HR 487, q.v.

Separation over time

Period: 467.7 y Eccentricity: 0.462 Now: 11.4", PA 184° -0.02" 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: 5.9 · B: 5.9 · Sep: 11.4″ · PA: 185° · 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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Compare Stars

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Spectral Classification

9

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map

10

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

Discover

14Stellar Notes

Alternative Names

With HR 487 called p Eridani.

15

Light Travel Time Machine

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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.

HIP 7588; Alpha Eridani

Bright naked-eye star, mag 0.5

Double Star mag 0.46 1.1° Eridanus

Elliptical galaxy

Galaxy mag 12.23 3.6° Tucana

HIP 5348; Zeta Phoenicis

Eclipsing binary, period 1.7d

Variable Star mag 3.92 4.5° Phoenix

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