Credit: Armen Akopian
Astronomical and Imaging Data
| RA: | 17h 48m 04.80s |
| DEC: | -24° 46′ 45.0″ |
| MAG: | 13.85 |
| Diameter: | 2.4′ |
| Const: | Sgr |
| OTA | ASA 1000RC |
| Focal Length | 6500mm |
| Camera | FLI PL16803 |
| Site | El Sauce, Chile |
| Sky Quality | Bortle 1 |
Useful Informations
Terzan 5 is a globular cluster located in the constellation Sagittarius, situated in the dense, heavily obscured central Galactic bulge of the Milky Way. Originally classified as a globular cluster, it’s now considered a unique and intriguing stellar system, possibly a relic of a disrupted dwarf galaxy or a primordial building block of the galactic bulge itself. This status is based on its unusual and complex stellar populations, which defy the conventional understanding of globular clusters as having a single stellar generation.
Unconventional Stellar Populations
Unlike typical globular clusters, which have a single stellar population with a uniform metallicity, Terzan 5 contains at least two distinct stellar populations with very different properties:
- An old, metal-poor population: Estimated to be around 12 billion years old, with a sub-solar metallicity ([Fe/H] ≈ -0.25).
- A younger, metal-rich population: With an age of about 4.5 billion years and a super-solar metallicity ([Fe/H] ≈ +0.27).
This remarkable discovery, along with the presence of a possible third, minor population, suggests that Terzan 5 experienced at least two separate bursts of star formation, separated by a quiescent period of billions of years. This multi-generational nature is a key reason why many astronomers now believe Terzan 5 is not a true globular cluster but rather the remnant of a much larger, more complex system.
Physical Characteristics
- Location and Obscuration: Terzan 5 is located about 15,000 light-years from Earth, deep within the Galactic bulge. This location makes it extremely difficult to observe in visible light due to significant interstellar reddening and extinction from dust and gas. Astronomers must use infrared and radio observations to penetrate this veil and study its stars.
- High Stellar Density: The cluster’s core is one of the densest stellar environments in the Milky Way, with a stellar density that exceeds 106 solar masses per cubic parsec. This extreme density leads to a high rate of stellar collisions and close encounters.
- Mass: Recent estimates suggest that Terzan 5 is significantly more massive than previously thought, with a mass of about 2 million times the mass of the Sun.
Millisecond Pulsars and X-ray Sources
The high stellar density of Terzan 5 has led to a prolific population of exotic objects. The cluster is known to host the largest population of millisecond pulsars (MSPs) of any globular cluster, with over 1300 being identified. These rapidly spinning neutron stars are thought to form through mass transfer in binary systems, which are more common in dense environments. Terzan 5 is also home to a number of X-ray sources, including a low-mass X-ray binary.