English: The Shield
Size Ranking: 84th
Area: 475 square degrees
Fully Visible: 74°N–90°S
The constellation of Scutum lies just south of the celestial equator in a rich area of the Milky Way between Aquila and Sagittarius. Scutum is a faint constellation introduced in 1684 by the Polish astronomer, Johannes Hevelius under the title Scutum Sobiescianum, Sobieski’s Shield, in honour of his patron, King John III Sobieski.
Rich Milky Way star fields are this constellation’s main attraction, notably the Scutum star cloud in its northern half which is about 6° across and reputedly the brightest part of the Milky Way outside Sagittarius.
The suggested path to Scutum is to locate αSco, Antares, and αAql, Altair, and, on the conjoint line, move from αSco to a point 60% along that line. This will have you arrive at a point in Scutum quite close to αSct. The green arrowed lines in the accompanying sky chart, pointing to αSco and αAql, respectively, should aid this task as too, but only on the meeting night, the arrowed lines indicating the direction of Jupiter on one hand and the Moon on the other.
Features of Interest:
αSct, at magnitude 3.8 is Scutum’s brightest star. It is an orange giant, 174ly away.
δSct, 187ly distant, is the prototype of a rare class of variable stars that pulsate in size every few hours,
producing small-amplitude brightness changes. This star is a white giant that varies from magnitude 4.6 to 4.8 with a period of 4 hours 39 minutes.
RSct, is a pulsating orange super-giant about 1400ly away that varies between magnitudes 4.2 and 8.6 in a 20 week cycle.
M11, the Wild Duck Cluster, is a show piece open cluster of about 200 stars, half the apparent width of the full Moon. At 6th magnitude, it is at the limit of naked eye visibility, but binoculars show it as a misty patch. In a telescope, with a magnification of around x100, it breaks up into a sparkling field of faint stardust. The cluster gets its popular name from the fact that its brightest members form a distinct fan shape, resembling a flight of ducks, an effect which is noticeable visually through a telescope but which becomes lost in long-exposure photographs. An 8th magnitude star, slightly brighter than the rest, lies at the fan’s apex. M11 is 6500ly away.
M26, is an open cluster of similar size to M11 but containing only about two dozen stars and hence much fainter. It lies about 5000ly away.
1. Redshift 2 – Maris Multimedia
2. The Guinness Book of Astronomy – Patrick Moore
3. Stars and Planets – Ian Ridpath and Wil Tirion
Sky Charts – Cartes du Ciel V 2.75
M11 The wild duck cluster http://apod.nasa.gov/apod/ap030122.html