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Sigma Ursae Majoris — Double Star in Ursa Major

HIP 45038; Sigma2 Ursae Majoris; 13 Ursae Majoris

Observable Double Star Good (59/100)

Sep: 4.7", Companion: mag 8.8

Magnitude 7.5–10.0m DoubleStar Ursa Major (UMa) Visible
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1Physical Properties

Magnitude 4.80
Spectral Type F6IV subgiant
Star Color Yellow (B-V 0.49)
Distance 58 ly

2Position & Identifiers

RA 09h 10m 23.2s
Dec +67° 08' 05.0"
Constellation Ursa Major (UMa)
HR 3616
HIP 45038
HD 78154
SAO 14788
Bayer Sigma2
Flamsteed 13 UMa
Double Cat 7203
SIMBAD Wikipedia

3How easy to split?

Primary 4.8 mag Companion 8.9 mag Separation 4.7″
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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. Hard+ Hard+ Hard+
150mm Newt. Medium+ Medium+ Medium+
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 Jan – Mar (peak: Feb)

5Multiple Star System Triple

Components 3 (triple)
Component IDs AB
Separation 4.7″
Companion Mag 8.8
Position Angle 346°
Star Colors A: Yellow B: Orange
Discoverer STF1306
AB 4.85 F7IV-V, 8.16 K2V, 1067.1y, a = 6.20". C, probably optical.

Separation over time

Period: 920.9 y Eccentricity: 0.793 Now: 4.7", PA 344° + 0.15" in 5 years
0.00" 1.5" 3.1" 4.6" 6.1" 2025 2030 2035 2040 2045 4.7"

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

Eyepiece View

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80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E 346°

A: 4.8 · B: 8.8 · Sep: 4.7″ · PA: 346° · 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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7

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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

ADS 7203B, 7.5 - 10.0v?
0.044".
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.

NGC 2787
Medium+
Barred spiral galaxy
Galaxy mag 10.8 2.2° Ursa Major
VY UMa
Medium
Semi-regular variable, range 5.9–6.5
Variable Star mag 6.00 9.1° Ursa Major
Show on Map

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