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51 Geminorum — Star in Gemini

Magnitude 5.0m Star Gemini (Gem) Visible
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1Physical Properties

Magnitude 5.00
Period 50 days
Variable Type Semi-Regular Variable (Late-type Giant)
Spectral Type M4IIIab bright giant
Star Color Red (B-V 1.66)
Distance 297 ly

2Position & Identifiers

RA 07h 13m 22.3s
Dec +16° 09' 32.0"
Constellation Gemini (Gem)
HR 2717
HIP 34909
HD 55383
SAO 96638
Flamsteed 51 Gem
Variable ID BQ Gem
SIMBAD

3How easy to spot?

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Equipment Bortle 3 Bortle 4 Bortle 5
Naked eye Medium Medium Hard+
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 Dec – Feb (peak: Jan)

5Survey Image

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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

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14Stellar Notes

SRb 6.63 - 7.01B, about 50d.
Wolf 630 group.
Also classified K3V, but this is not consistent with type of light variability.
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 2355
Easy
Open cluster
Open Cluster mag 10.0 2.6° Gemini
Mekbuda
Zeta Gem
Medium
Pulsating variable, period 10.1d
Variable Star mag 3.79 4.9° Gemini
NGC 2418
Hard+
Elliptical galaxy
Galaxy mag 13.0 5.8° Gemini
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