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Iota Leonis — Double Star in Leo

Observable Double Star Good (55/100)

Sep: 2.4", Companion: mag 6.7

Magnitude 3.9m DoubleStar Leo Visible
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1Physical Properties

Magnitude 3.94
Variable Type Delta Scuti (Pulsating)
Spectral Type F3V
Star Color Yellow-white (B-V 0.41)
Distance 77 ly

2Position & Identifiers

RA 11h 23m 55.5s
Dec +10° 31' 45.0"
Constellation Leo
HR 4399
HIP 55642
HD 99028
SAO 99587
Bayer Iota
Flamsteed 78 Leo
Double Cat 8148
SIMBAD

3How easy to split?

Primary 3.9 mag Companion 6.7 mag Separation 2.4″
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Telescope Bortle 3 Bortle 4 Bortle 5
80mm refr. Hard Hard Hard
150mm Newt. Medium Medium Medium
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 Feb – Apr (peak: Mar)

5Multiple Star System

Separation 2.4″
Companion Mag 6.7
Position Angle 89°
Star Colors A: Yellow-white B: Orange
Discoverer STF1536
4.03 F2IV, 6.70 G3V, 192.0y, a = 1.92"; possible subsystem with period about 16y. Combined mag., colors. Combined | mass about 3 Suns.

Separation over time

Period: 189.6 y Eccentricity: 0.550 Now: 2.4", PA 88° + 0.10" in 5 years
0.00" 0.77" 1.5" 2.3" 3.1" 2025 2030 2035 2040 2045 2.4"

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 89°

A: 3.9 · B: 6.7 · Sep: 2.4″ · PA: 89° · N up, E right

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

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7

Size Comparison

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8

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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

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15Stellar Notes

Delta Sct?
192y, K 2.5k/s, V0 -11.0k/s, asini 2030. Orbit questioned by Morbey and Griffin (1987, ApJ, 317, 343).
UMa stream.
0.052".
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.

M66
NGC 3627
Easy
Bright spiral galaxy
Galaxy mag 9.0 2.6° Leo
56 Leo
Hard+
Semi-regular variable, range 5.7–6.0
Variable Star mag 5.81 8.2° Leo
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