About NGC 6397
Description
NGC 6397 is one of the nearest globular clusters to Earth, at about 7,800 light-years away in Ara. At magnitude 5.7, it is visible to the naked eye from dark sites. It has an unusual core-collapsed structure, meaning its center has become extremely dense.
Observing Tips
A superb target visible to the naked eye as a fuzzy star. Binoculars show a granular ball. Any telescope resolves it into a beautiful field of stars. Notable for its lack of a bright concentrated core — a hallmark of core collapse. Best in summer from southern locations.
History
Discovered by Nicolas Louis de Lacaille in 1751 from South Africa. It is one of the two nearest globular clusters (along with M4) and has been extensively studied by the Hubble Space Telescope.
Fun Facts
NGC 6397 has undergone core collapse, a gravitational process where the most massive stars sink to the center, creating an extremely dense core. Hubble images revealed a population of faint blue stars in its core — helium-core white dwarfs in binary systems.
Observe
1Properties
Position & Identifiers
2How easy to spot?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | Easy | Easy | Easy |
| 150 mm Newton 150mm Newt. | Easy | Easy | Easy |
| Celestron C8 (203 mm SCT) C8 203mm | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
3Visibility
Set a location in User Settings to see visibility data.
4
Eyepiece View
NGC 6397 · 15.3′ diameter · N up, E left
5
Best Magnification
6Metallicity
[Fe/H] = -2.02 — these stars formed from gas about 105× poorer in iron than the Sun.
7Concentration class
Shapley-Sawyer class I — extremely centrally concentrated core.
Explore
8
Classification Decoder
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.
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