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Nunki — Star in Sagittarius

HIP 92855; Sigma Sagittarii; 34 Sagittarii

Magnitude 2.0m Star Sagittarius (Sgr) Visible
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About Nunki

Description

Nunki is a blue main-sequence star of spectral type B2.5V at magnitude 2.02 in Sagittarius. Located about 228 light-years from Earth, it has a luminosity of roughly 3,300 times solar and a surface temperature of about 20,000 K. It is the second brightest star in Sagittarius and forms the handle-top of the Teapot asterism.

Observing Tips

Nunki forms the top of the Teapot handle in Sagittarius, northeast of Kaus Australis. It is a brilliant blue-white star, noticeable among the warm-colored stars in the region. The Moon occasionally occults Nunki, creating a dramatic event. Best observed July through September.

History

The name Nunki is one of the oldest known star names, of Babylonian origin, though its exact meaning is lost. It appears on the 'Euphratean' star lists and is at least 4,000 years old. In modern usage, the name was preserved through R.H. Allen's influential 1899 book Star Names: Their Lore and Meaning.

Fun Facts

Nunki is one of the few star names that can be traced directly to ancient Babylonian astronomy, making it possibly the oldest star name in current use. Its position on the ecliptic means the Moon and planets regularly pass near it.

Observe

1Physical Properties

Magnitude 2.02
Spectral Type B2.5V
Star Color Blue (B-V -0.22)
Distance 228 ly

2Position & Identifiers

RA 18h 55m 15.9s
Dec -26° 17' 48.0"
Constellation Sagittarius (Sgr)
HR 7121
HIP 92855
HD 175191
SAO 187448
Bayer Sigma
Flamsteed 34 Sgr
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 May – Jul (peak: Jun)

5Survey Image

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Explore

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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

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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

Discover

15Stellar Notes

Interferometer measures indicate multiple star.
Color excess E(B-V) = +0.02.
Sco-Cen assoc.
Lyman alpha and Lyman beta observed from COPERNICUS.
NUNKI; Sadira.
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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 6717
Medium+
Compact globular cluster
Globular Cluster mag 10.35 3.6° Sagittarius
Collinder 394
Easy
Open cluster
Open Cluster mag 6.3 6.1° Sagittarius
V3879 Sgr
Medium
Semi-regular variable, range 6.0–6.6
Variable Star mag 6.35 7.6° Sagittarius
Show on Map

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