57 Cancri — Double Star in Cancer

Observable Double Star Fair (33/100)

Sep: 1.5", Companion: mag 6.4

Magnitude 5.4^m DoubleStar Cancer (Cnc) Visible

Star Map + List + Plan Star Hop

Observe

1Physical Properties

Magnitude 5.39

Spectral Type G7III giant

Star Color Orange (B-V 1.05)

Distance 652 ly

2Position & Identifiers

RA 08h 54m 14.7s

Dec +30° 34' 46.0"

Constellation Cancer (Cnc)

HR 3532

HIP 43721

HD 75959

SAO 61125

Flamsteed 57 Cnc

Double Cat 7071

3How easy to split?

Primary 5.4 mag Companion 6.4 mag Separation 1.5″

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

Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Dec – Feb (peak: Jan)

5Multiple Star System Triple

Components 3 (triple)

Component IDs AB

Separation 1.5″

Companion Mag 6.4

Companion Sp K0

Position Angle 310°

Star Colors A: Orange B: Orange

Discoverer STF1291

Notes

AB binary. B is K0.

Separation over time

Period: 2336.1 y Eccentricity: 0.796 Now: 1.5", PA 308° + 0.01" 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: 5.4 · B: 6.4 · Sep: 1.5″ · PA: 310° · N up, E right

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

Explore

6

Size Comparison

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7

Compare Stars

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8

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

See HR 3464.

15

Light Travel Time Machine

16

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 44154; Sigma3 Cancri; 64 Cancri

Easy double, sep 90.3″

Double Star mag 5.20 2.2° Cancer

Easy double, sep 4.5″

Double Star mag 5.82 2.3° Cancer

HIP 43103; Iota Cancri; 48 Cancri

Colorful double, sep 30.6″

Double Star mag 4.02 2.4° Cancer

Galaxy mag 9.7 2.9° Lynx

Semi-regular variable, range 5.3–6.9

Variable Star mag 5.95 3.5° Cancer

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