Credit: Jim Fordice
Astronomical and Imaging Data
| RA: | 09h 20m 57.07s |
| DEC: | -77° 16′ 54.8″ |
| MAG: | 11.35 |
| Diameter: | 10′ |
| Const: | Cha |
| OTA | 20” AG Optical iDK |
| Focal Length | 3403mm |
| Camera | FLI ProLine16803 |
| Site | Hakos, Namibia |
| Sky Quality | Bortle 1 |
Useful Informations
The globular cluster E 3 (also known by its alternate designation C0921−770) is a low-mass globular cluster belonging to the Milky Way Galaxy. It is primarily notable for exhibiting signs of tidal disruption, indicating that it is losing mass due to the gravitational forces exerted by the galaxy.
Key Properties and Location
E 3 is situated in the outer regions of the Milky Way, with a distance from the Sun (R⊙) of approximately 8.1 kiloparsecs (kpc) and a Galactocentric radius (Rgc) of about 9.1 kpc. Its relatively low galactic latitude suggests it may not be a typical halo globular cluster, which are usually found further away from the galactic plane.
Stellar Population and Metallicity
Like most globular clusters, E 3 is comprised of very old stars, typically classified as Population II stars, which are characterized by a low abundance of heavy elements (metals). Its estimated metallicity, represented by the iron abundance ratio [Fe/H], is typically listed in catalogs, but specific, uniformly agreed-upon values vary among different studies. Generally, globular clusters are metal-poor relative to the Sun.
Dynamical State and Disruption
A significant focus of recent research on E 3 is its dynamical state. Observations suggest it is a low-mass cluster currently undergoing a process of tidal disruption.
- Tidal Disruption: Studies have identified an extended structure emerging from the cluster, extending up to about one degree from its center. This low surface-brightness structure is interpreted as a tidal tail—a stream of stars being pulled away from the cluster by the Milky Way’s powerful tidal gravitational field.
- Orbital Implication: These tidal tails are found to be aligned with the direction toward the Galactic center, which is characteristic of a cluster nearing or passing through its perigalacticon (the point of closest approach to the Galactic center) in its orbit. The presence of this structure implies the cluster has lost a substantial amount of its original mass and is likely to continue to be disrupted over time.
This makes E 3 a valuable object for studying the processes of globular cluster evolution and how these ancient stellar systems are eventually destroyed by the gravitational influence of their host galaxy.