English: The Set Square
Size Ranking: 74th
Area: 165 square degrees
Fully Visible: 29°N – 90°S.
This constellation is relatively superfluous and lies in a rich region of the Milky Way between Ara and Lupus. It was introduced in the 18th century by the French astronomer Nicolas Louis de Lacaille, originally under the successive names of Quadra Euclidis (Euclid’s Quadrant) and Norma et Regula, the set square and ruler. It adjoins another Lacaille invention, Circinus, the compasses.
Its current constituent stars were previously part of Ara, Lupus and Scorpius. Since Lacaille’s time the boundaries of Norma have been altered, so that the stars that were αNormae and βNormae have been reabsorbed into Scorpius where they are know anonymous.
This constellation can be found by running a line, starting at αCru, the ‘bottom’ star of the Southern Cross, and extending past αCen, the brighter of the two Pointers, as far again, where it arrives at γNor.
Features of Interest:
γ2Nor,is the brightest star in this constellation and is a yellow giant star 128ly away, magnitude 4.0. Next to it lies the far more distant yellow-white supergiant, γ1Nor, magnitude 5.0 and 1500ly distant. These two components are considered to form an unrelated double, separation 27’.
δNor, is a white star, magnitude 4.7 and 123ly away.
εNor, is a double star, separation 22.8”, PA 335°.It is 400ly away and its components are magnitudes 4.5 and 6.7.
ιNor, appears in small telescopes as a double star with component magnitudes, 4.6 and 8.1. The brighter star is itself a very close binary, separation 0.2”, PA 100°, with component parts of magnitude 4.8 and 7.5, divisible only with very large telescopes. The orbital period of this binary is 27yrs.
NGC6087, is a loose, large binocular cluster of about 40 stars, 3000ly away, with chains of stars extending from it like spider’s legs. At its center lies its brightest star, the Cephied variable, SNor, which ranges in magnitude from 6.1 to 6.8 in 9.8 days.
Shapley1, known variously as SP1, PK329+02.1 or RCW 100, is a symmetrical planetary nebula. Of 13th magnitude, it requires larger apertures to be seen. The central star is of 14th magnitude.
Beautiful emission nebula NGC 6164 was created by a rare, hot, luminous O-type star, some 40 times as massive as the Sun. Seen at the center of the cosmic cloud, the star is a mere 3 to 4 million years old. In another three to four million years the massive star will end its life in a supernova explosion. Spanning around 4 light-years, the nebula itself has a bipolar symmetry. That makes it similar in appearance to more familiar planetary nebulae – the gaseous shrouds surrounding dying sun-like stars. Also like many planetary nebulae, NGC 6164 has been found to have an extensive, faint halo, revealed in this deep telescopic image of the region. Expanding into the surrounding interstellar medium, the material in the halo is likely from an earlier active phase of the O star. The gorgeous skyscape is a composite of narrow-band image data highlighting the glowing gas, and broad-band data of the surrounding starfield. NGC 6164 is 4,200 light-years away in the southern constellation of Norma.
1. Redshift 2 – Maris Multimedia
2. The Guinness Book of Astronomy – Patrick Moore
3. Stars and Planets – Ian Ridpath and Wil Tirion
4. Sky Charts – Cartes du Ciel V 2.75.
5. Where the Stars Are – Orion..
6. http://apod.nasa.gov/apod/ap060606.html Astronomy Picture of the Day 2006 June 6