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Sigma Herculis — Star in Hercules

Magnitude 4.2m Star Hercules (Her) Visible
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1Physical Properties

Magnitude 4.20
Spectral Type B9V
Star Color Blue-white (B-V -0.01)
Distance 326 ly

2Position & Identifiers

RA 16h 34m 06.2s
Dec +42° 26' 13.0"
Constellation Hercules (Her)
HR 6168
HIP 81126
HD 149630
SAO 46161
Bayer Sigma
Flamsteed 35 Her
SIMBAD

3How easy to spot?

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Equipment Bortle 3 Bortle 4 Bortle 5
Naked eye Medium+ Medium+ Medium
50mm finder Easy Easy Easy
150mm scope Easy Easy Easy
Easy Medium Hard Very hard Impossible

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

4Visibility

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Best season Apr – Jun (peak: May)

5Survey Image

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7

Size Comparison

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8

Compare Stars

9

Spectral Classification

10

Hertzsprung-Russell Diagram

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Read: The Hertzsprung-Russell Diagram — Reading Stars Like a Map
11

Stellar Lifecycle

12

Blackbody Spectrum

13

Stellar Absorption Spectrum

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

14

Stellar Fusion

Discover

15Stellar Notes

Sep. 0.067". Noted as double by speckle interferometry in 1971-2, unresolved at Mayall 4-meter in 1976. Spectrum | double-lined. Resolved by speckle observations 1986.45 (Blazit et al. 1987, A&AS, 71, 57).
16

Light Travel Time Machine

17

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.

30 Her
Easy
Mira-type variable, range 4.3–6.3
Variable Star mag 5.04 1.2° Hercules
NGC 6239
Hard+
Barred spiral galaxy
Galaxy mag 12.3 3.0° Hercules
NGC 6229
Easy
Globular cluster — dense ball of ancient stars
Globular Cluster mag 9.4 5.6° Hercules
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