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Elnath — Star in Taurus

HIP 25428; Beta Tauri; 112 Tauri

Star Taurus (Tau) Visible
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About Elnath

Description

Elnath (Beta Tauri) is the second brightest star in Taurus at magnitude 1.65, located about 134 light-years from Earth. It is a blue-white giant of spectral type B7III, about 4.5 times the mass of the Sun and 700 times more luminous. Elnath marks the tip of the northern horn of Taurus the Bull. It lies very close to the galactic anticenter — the point in the sky directly opposite the center of the Milky Way.

Observing Tips

Elnath is shared visually between Taurus and Auriga, sitting at the boundary where the Bull's horn meets the Charioteer's foot. It serves as a useful guide star — the supernova remnant M1 (Crab Nebula) lies about 1 degree to its northwest, and the open clusters of Auriga (M36, M37, M38) are nearby. Its blue-white color is evident to the naked eye. Best observed from November through March.

History

The name Elnath comes from the Arabic 'al-Natih' meaning 'the butting one,' referring to the tip of the bull's horn. Historically, the star was shared between the constellations Taurus and Auriga and carried the dual designation of Beta Tauri and Gamma Aurigae. In 1930, when the IAU formalized constellation boundaries, it was officially assigned to Taurus.

Fun Facts

Elnath is one of the few bright stars that was reassigned between constellations when modern boundaries were drawn. Its position near the galactic anticenter means that when you look at Elnath, you are looking outward through the disk of the Milky Way, away from the galactic center in Sagittarius.

Observe

1Physical Properties

Magnitude 1.65
Spectral Type B5.5IV
Star Color Blue-white (B-V -0.13)
Distance 134 ly

2Position & Identifiers

RA 05h 26m 17.5s
Dec +28° 36' 27.0"
Constellation Taurus (Tau)
HR 1791
HIP 25428
HD 35497
Bayer Beta
Flamsteed 112 Tau

3How easy to spot?

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Equipment Bortle 3 Bortle 4 Bortle 5
Naked eye Easy Easy Easy
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 Nov – Jan (peak: Dec)

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Size Comparison

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Spectral Classification

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Hertzsprung-Russell Diagram

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Stellar Lifecycle

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Blackbody Spectrum

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Stellar Absorption Spectrum

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

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Stellar Fusion

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14Stellar Notes

Color excess E(B-V) = 0.00.
Member of Pleiades group.
Manganese star.
Expanding circumstellar shell.
ALNATH; EL NATH; Nath. Beta Tau is also Gamma Aur, in Taurus.
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Light Travel Time Machine

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Relativistic Travel

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