Norma
What is Norma?
Constellations· Southern winter · in the Milky Way between Scorpius and Lupus. Lacaille's tribute to the carpenter's set square. Its stars are faint, but it lies in the thick of the Milky Way and is rich in star clusters.
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Stars of the figure
| Star | Magnitude |
|---|---|
| Gamma2 Normae | 4.0 |
| Epsilon Normae | 4.5 |
The 2 brightest of the 2 stars used in the figure (1 lines). Lower magnitude means brighter.
Constellation basics
| Season | Jun–Jul evenings; only its northern edge grazes the horizon from New York; not visible from London |
|---|---|
| Brightest star | γ² Normae, mag 4.0 |
| How to find | west of the Scorpion's tail, southeast of Lupus |
| Area rank | 74th of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
A spiral arm named after a constellation — the Norma Arm
The Milky Way is a spiral galaxy, with several arms curling out from its centre like a whirlpool. One of them is named after this constellation: the Norma Arm. It lies closer to the galactic centre than the Sun does. Seen from Earth, a long stretch of it lines up in the direction of Norma, which is how it got its name.
Because we live inside the Milky Way, we cannot look down on it from outside. Instead, scientists used radio telescopes to observe hydrogen gas and worked out where the arms are from how fast the gas moves. The Sun sits in the small Orion Arm, between the Sagittarius Arm and the Perseus Arm. Norma has so many star clusters because we are looking along the length of an arm.
The constellation in depth
Norma is one of the constellations Lacaille made in the 1750s to honour scientific instruments. First called the Set Square and Rule, it pairs with its neighbour Circinus, the compass. When constellation boundaries were redrawn later, its original alpha and beta stars went to Scorpius, so today Norma has no alpha star and Gamma serves as its brightest.
Even that Gamma is really two stars. Gamma-2 is a giant of magnitude 4.0 about 130 light-years away. Gamma-1 beside it is a little fainter at magnitude 5.0, yet it is a yellow supergiant some 1,500 light-years off. It looks almost as bright from more than ten times farther away because it truly shines far more strongly.
In the middle of the Milky Way, Norma is rich in open clusters, loose groups of stars born together; NGC 6087 and NGC 6067 show even in binoculars. About 200 million light-years beyond lies the Norma galaxy cluster. Scientists think it sits near the centre of the Great Attractor, a vast concentration of mass pulling on many galaxies, including our own.
At declinations of −42° to −60°, only the top of the constellation grazes the southern horizon from New York around midnight in June and July, and from London it never rises. From the southern hemisphere, look in the Milky Way west of the Scorpion's tail on June and July evenings. In the Sky view, set Sydney on a July evening and it appears beside the tail.
Frequently asked
- When can I see Norma?
- Norma is best seen in Jun–Jul evenings; only its northern edge grazes the horizon from New York; not visible from London.
- How do I find Norma?
- To find Norma, look for west of the Scorpion's tail, southeast of Lupus.
- What is the brightest star in Norma?
- The brightest star in Norma is Gamma2 Normae, at magnitude 4.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.