Astronomers have made an exciting discovery by detecting multiple extended tidal tails associated with the old globular cluster NGC 288. This finding could provide valuable insights into the cluster’s internal dynamics and the evolution of the Milky Way galaxy. The observations reveal a complex network of stellar streams that offer clues about the gravitational interactions shaping this ancient celestial body. Globular clusters are dense collections of stars that offer a unique window into the early history of our galaxy.
Unraveling the Intricate Tidal Tails of NGC 288
A group of astronomers, led by Carl J. Grillmair from the California Institute of Technology (Caltech), has identified something truly unique about the ancient globular cluster NGC 288 using dense data from several astronomical surveys. The researchers launched several extended tidal tails linked to this cluster, suggesting a turbulent and new lifetime.
Tidal tails appear in stars and interstellar gas flows off the interacting galaxies. Such features are the result of gravitational interactions between galaxies and star clusters. The pictures show that interacting objects are equipped with only a single tail or (at least) two tails. Analyzing the properties of these tidal tails can be a goldmine of information about the tides experienced by the cluster and its internal dynamics, and can even cast light on the evolution history of the cluster as well as provide a constraint on Toarcian models for dark matter in galaxies.
Exploring the Stellar Streams of NGC 288
The researchers found a strong over-density of stars even 40 degrees away from NGC 288, along the meridian 300 degrees, and then gradually to about 80 degrees continuing in a northern direction from the cluster before blending into the Galactic disk. The ‘leading tail’ is consistent with two or more spatially offset and kinematically separate stellar streams, each about 650 light-years across.
The astronomers also detected a ‘trailing tail’ pointing up and to the right of the image, which is around 35-70 degrees long. In the sky, the trailing tail actually turned out to be much fainter than the leading tail Coincidentally, a stream model including an infalling Large Magellanic Cloud that weights substantially similar to our own Milky Way satellite yields a trailing tail also well-aligned in position.
Shedding Light on the Milky Way’s Evolution
The presence of these tidal tails in NGC 288, and the fact that they are so complex, provides important insights into how both globular clusters evolve in general and, more specifically, the Milky Way galaxy itself. The researchers note that if only a small number of the distant candidates can be confirmed as once having been members of NGC 288, this stream will become an “important constraint on the shape of the inner halo potential” and be used to help us better understand the effect of the LMC and other Galatic constituents.
Additional studies, with follow-up radial velocity measurements, will be needed to ultimately establish that these stars are indeed members of NGC 288 tidal streams. This knowledge might be used to understand better the clumpiness of dark matter in our galaxy and give more information on how this old globular cluster has evolved.
