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Deneb Algedi — Star in Capricornus

HIP 107556; Delta Capricorni; 49 Capricorni

Magnitude 2.8–3.0m Star Capricornus (Cap) Visible
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About Deneb Algedi

Description

Deneb Algedi is a white star of spectral type Am (metallic-line A) at magnitude 2.87, the brightest star in Capricornus. Located about 39 light-years from Earth, it has a luminosity of about 8 times solar. It is an eclipsing binary with a very small amplitude, completing one orbit every 1.02 days.

Observing Tips

Deneb Algedi marks the eastern (tail) end of Capricornus. It is the brightest star in this faint zodiacal constellation and a useful anchor for identifying the rest of the figure. Best observed August through November.

History

The name Deneb Algedi comes from the Arabic 'dhanab al-jady,' meaning 'the tail of the kid (young goat).' Capricornus is one of the oldest recognized constellations, associated with the sea-goat figure since Babylonian times over 4,000 years ago.

Fun Facts

At only 39 light-years, Deneb Algedi is one of the nearest bright stars in the zodiac. Its Am spectral type indicates enhanced metallic lines in its atmosphere — a chemical peculiarity caused by atomic diffusion in its relatively calm outer layers.

Observe

1Physical Properties

Magnitude 2.87
Range 2.83 - 3.05
Period 24.5 hours
Variable Type Eclipsing Binary (Algol-type)
Spectral Type A5MF2 (IV)
Star Color Yellow-white (B-V 0.29)
Distance 39 ly

2Position & Identifiers

RA 21h 47m 02.4s
Dec -16° 07' 38.0"
Constellation Capricornus (Cap)
HR 8322
HIP 107556
HD 207098
SAO 164644
Bayer Delta
Flamsteed 49 Cap
Variable ID Del Cap
Double Cat 15314
SIMBAD Wikipedia

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 Jul – Sep (peak: Aug)

5Survey Image

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Size Comparison

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Spectral Classification

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Hertzsprung-Russell Diagram

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

EA (possibly RS CVn type) 2.83 - 3.05V, 1.0227789d. Form of light curve varies.
ADS 15314A. Component A is SB, 3.2, 5.2v, 0.0018"; B, 15.8v, 69"; C 12.7v, 120".
1.0228d, K 70.8k/s, V0 -0.2k/s, asini 0.996.
Delta Sct spectrum. Also classified Delta Del, A7mIII.
Deneb Algedi; Deneb Algiedi; Scheddi; Sheddi.
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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.

NGC 7180
Hard+
Elliptical galaxy
Galaxy mag 12.5 5.7° Aquarius
M30
NGC 7099
Easy
Globular cluster — dense ball of ancient stars
Globular Cluster mag 7.5 7.2° Capricornus
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