Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 17h 50m 13.06s |
| DEC: | -37° 03′ 05.2″ |
| MAG: | 7.15 |
| Diameter: | 9.6′ |
| Const: | Sco |
| OTA | ASA 1000RC |
| Focal Length | 6500mm |
| Camera | FLI PL16803 |
| Site | El Sauce, Chile |
| Sky Quality | Bortle 1 |
Useful Informations
NGC 6441 is one of the most massive and luminous globular clusters in the Milky Way. Located in the constellation Scorpius, it is a scientifically significant object due to its location in the Galactic bulge, its exceptionally high stellar density, and its complex, multi-generational stellar population.
Physical Characteristics
- Distance: Located approximately 44,000 light-years from Earth.
- Mass: It is one of the most massive globular clusters in our galaxy, with an estimated mass of about 1.6 million solar masses.
- Concentration: NGC 6441 is a Shapley-Sawyer Concentration Class III, indicating a very high central stellar density. Its core is so dense that it’s challenging to resolve individual stars.
- Age: The cluster is very old, with an estimated age of around 11.5 billion years.
Unique Stellar Populations
- Split Red Giant Branch: Like NGC 6388, NGC 6441 exhibits a split red giant branch in its color-magnitude diagram. This feature is strong evidence for the existence of at least two distinct stellar populations with different helium abundances. The second population is thought to have formed from gas enriched by the processed material of the first generation of stars.
- Oosterhoff Type II Anomaly: NGC 6441 is an anomalous cluster because it has a relatively high metallicity ([Fe/H] ≈ -0.5 dex) but is classified as an Oosterhoff Type II cluster based on the long pulsation periods of its RR Lyrae variable stars. This type is usually associated with very metal-poor clusters.
Black Holes and Pulsars
- Intermediate-Mass Black Hole (IMBH): The cluster’s high mass and high stellar density make it a prime candidate for hosting an intermediate-mass black hole. While no conclusive evidence has been found, some kinematic studies hint at its presence.
- Pulsars: NGC 6441 is home to several millisecond pulsars, which are rapidly spinning neutron stars that emit pulses of radiation. These pulsars are often found in globular clusters due to the high rate of close stellar encounters that can form binary systems.