σ Sagittarii

Sigma Sagittarii is the second brightest star in the constellation, after epsilon. Its significance in this central asterism lies in its name, ‘Nunki’, the “Star of the Proclamation of the Sea”, a title that supposed refers to the other constellations that will follow, such as Aquarius and Pisces.

Sigma is the northernmost star in this striking asterism, called variously the Milk Dipper (as its handle–lambda–extends into the Milky Way) or the Teapot. Seen upside down in the north, these names mean less than they would in the Southern Hemisphere.

The star on the southeastern edge, zeta Sagittarii, is a multiple system (HdO 150):
      AB: 3.3, 3.5; 267º, 0.5" with an orbit of 21.14 years.
      AB-C: 2.6, 10.6; 302º, 72.6".

West-southwest of zeta 1.5º is the Messier object M54. Although with an apparent magnitude of 7.6, this globular cluster is best seen larger telescopes, which bring out the colour contrast of a yellow core surrounded by bluish stars.


Centring sigma in your field of view, move one binocular field due north. The brightest star here is pi Sagittarii.

On the southwestern edge of your field of view is nu1 (BU 1033)AB: 4.9, 10.8; 97º, 2.5".

A straight line drawn from nu1 through the centre of the field of view, to the northeast, gets you to h5082, a very nice triple:
      AB: 6.2, 9.0; 88º, 7.4".
      AC: 6.2, 10.8; 112º, 20.0".

If you drop back down to the ‘Milk Dipper’ asterism, then move about one and a half fields northeast, you'll find an isolated and upside-down triangle of dimmer stars: binoculars. Nearly as bright as the chi stars here, at the lower tip of this triangle is H N 119, a fine telescopic binary: 5.6, 8.8; 146º, 7.7".

One field southeast of this view, in a bleak part of the skies, is M55, a bright 6.3m globular cluster made up of many thousands of stars, nicely appreciated in smaller telescopes and glorious in larger scopes—mostly bright blue stars with a scattering of red members, which gave it the name some observers know it by: the Summer Rose Star.

To continue click on epsilon on the map.

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© 1999-2014 by Richard Dibon-Smith.