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Aldebaran

HIP 21421; Alpha Tau; 87 Tau

HIP 21421; Alpha Tau; 87 Tau DoubleStar Tau Visible Level 3 Medium telescope (6-8") - Requires steady seeing
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Physical Properties

Magnitude 0.85
Variable Type Slow Irregular Variable
Spectral Type K5III
Star Color Red (B-V 1.54)
Temperature 3881 K
Radius 44.3 R☉
Distance 64.7 ly

Position & Identifiers

RA 04h 35m 55.2s
Dec +16° 30' 33.0"
Constellation Tau
HR 1457
HIP 21421
Bayer Alpha
Flamsteed 87 Tau
Variable ID Alp Tau
Double Cat 3321

Visibility

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Multiple Star System

Components 6
Component IDs AC
Separation 31.4″
Companion Mag 13.6
Companion Sp M2
Position Angle 115°
Star Colors A: Red B: Red
Discoverer BU 550

Eyepiece View

80x Dawes: 1.9″ TFOV: 0.6°
Realistic = true angular size
N E 115° A (0.8) B (13.6)

Sep: 31.4″ · PA: 115° · N up, E left

Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 3.1″

Size Comparison

Stellar Lifecycle

Spectral Classification

Hertzsprung-Russell Diagram

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Blackbody Spectrum

Stellar Absorption Spectrum

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

Stellar Notes

Lb 0.75 - 0.95V. Var. H and K emission.
AB binary. B is 13.5v, dM2 at 31". CD, 122" from A is 11.2, 13.6v sep. 2" also binary but independent of AB.
Hyades group.
IR emission envelope diam. 10". MgII emissions indicate a cooler shell surrounding the supergiant.
0.048".
ALDEBARAN; Cor Tauri; Parilicium.
Diam. Two determinations, 0.022" and 0.0237".

Survey Image

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About Aldebaran

Description

Aldebaran is an orange giant star of spectral type K5III, the brightest star in the constellation Taurus at magnitude 0.85. It is located about 65 light-years from Earth and is roughly 44 times the diameter of the Sun and 425 times more luminous. Aldebaran appears to be part of the Hyades star cluster but is actually a foreground star, less than half the distance to the cluster. It is a slightly irregular variable star with small amplitude variations.

Observing Tips

Aldebaran is easy to find by extending the line of Orion's Belt to the upper right. Its deep orange color is immediately apparent and makes a fine contrast with the blue Pleiades cluster about 12 degrees to its northwest. Through binoculars, the surrounding Hyades cluster provides a rich star field with Aldebaran as the jewel at its center. The Moon regularly occults Aldebaran (in certain years), offering dramatic disappearance and reappearance events visible through small telescopes. Best observed from November through March.

History

The name Aldebaran comes from the Arabic 'al-Dabaran' meaning 'the follower,' because it appears to follow the Pleiades across the sky. It was one of the four Royal Stars of ancient Persia (along with Regulus, Antares, and Fomalhaut), marking the vernal equinox around 3000 BC. Ptolemy listed it in the Almagest as one of the brightest stars in the sky.

Fun Facts

In 1997, a planet was tentatively detected orbiting Aldebaran — Aldebaran b, a gas giant about 6 times the mass of Jupiter with a 629-day orbit — though the claim has been debated. Aldebaran was the target of the Pioneer 10 spacecraft; if the probe were still headed that way, it would reach the star's vicinity in about 2 million years.