Alpha Doradus — Double Star in Dorado

Magnitude 3.3^m DoubleStar Dorado (Dor) Visible

Star Map + List + Plan

About Alpha Dor

Description

Alpha Doradus is a white giant of spectral type A0IIISi at magnitude 3.27, the brightest star in Dorado (the Swordfish). Located about 176 light-years from Earth, it is a chemically peculiar silicon star. Dorado is best known for containing the Large Magellanic Cloud.

Observing Tips

Alpha Dor lies in the far southern sky near the Large Magellanic Cloud (LMC). It is the brightest star in the otherwise faint constellation Dorado. Only visible from the southern hemisphere. Best observed November through February.

History

Dorado was created by Petrus Plancius from Dutch navigators' observations and represents a dolphinfish (mahi-mahi). Alpha Doradus has no traditional proper name. The constellation is famous for containing the LMC and the Tarantula Nebula.

Fun Facts

Dorado's main claim to fame is hosting the Large Magellanic Cloud — our galaxy's most prominent satellite galaxy, visible to the naked eye from the southern hemisphere. Alpha Dor serves as a guide to this spectacular object.

Observe

1Physical Properties

Magnitude 3.27

Range 3.24 - 3.28

Period 2.9 days

Variable Type Alpha2 CVn (Magnetic Rotating)

Spectral Type B7V

Star Color Blue-white (B-V -0.10)

Distance 169 ly

2Position & Identifiers

RA 04h 33m 59.8s

Dec -55° 02' 42.0"

Constellation Dorado (Dor)

HR 1465

HIP 21281

HD 29305

SAO 233564

Bayer Alpha

Variable ID Alp Dor

3How easy to spot?

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Equipment	Bortle 3	Bortle 4	Bortle 5
Naked eye Naked eye	Easy	Easy	Medium+
50 mm finder 50mm finder	Easy	Easy	Easy
150 mm telescope 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 Oct – Dec (peak: Nov)

5Light Curve

6Multiple Star System Triple

Components 3 (triple)

Separation 0.3″

Companion Mag 4.6

Position Angle 115°

Star Colors A: Blue-white B: White

Discoverer B 2092

Notes

3.8 A0IIIp, 4.3 B9IV, 13.00y, a = 0.212". Combined mag., colors. Companion 10v at 78" optical.

Separation over time

Period: 12.1 y Eccentricity: 0.777 Now: 0.29", PA 140° -0.03" in 5 years

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

Explore

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Size Comparison

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Compare Stars

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Spectral Classification

11

Hertzsprung-Russell Diagram

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

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Stellar Lifecycle

13

Blackbody Spectrum

14

Stellar Absorption Spectrum

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

15

Stellar Fusion

Discover

16Stellar Notes

Variable Star

Alpha CV 3.26 - 3.30V, amp. 0.10u, 2.943d.

Group/Cluster

Member of Pleiades group.

17

Light Travel Time Machine

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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.

Barred spiral galaxy

Galaxy mag 10.4 0.6° Dorado

HIP 22531; Iota Pictoris

Easy double, sep 12.3″

Double Star mag 5.61 2.9° Pictor

Semi-regular variable, range 4.8–6.6

Variable Star mag 5.40 7.0° Dorado

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