Tidal shock

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A tidal shock occurs when a star cluster or other distributed astronomical object passes by a large mass such as an interstellar cloud, resulting in gravitational perturbation on a time scale that is much less than the mean time for a star to complete an orbit within the cluster. The tidal force from this event can increase the dynamic energy of the cluster, in effect heating it up. This causes the cluster to expand and shed some of the outer stars. [1]

Tidal shocks occur, for example, when a globular cluster passes through the galactic plane or near the core of the Milky Way. These events are an important factor during the early evolution of a globular cluster. They work to truncate the outer part of clusters, thereby limiting the impact of future tidal shocks. [2] Streams of stars shed from a globular cluster as a result of tidal shock can form what are termed tidal tails. These are extended streams of stars that lead away from the cluster. [3] Such streams can be used to trace the orbital path of the cluster. [4]

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NGC 4147 Globular cluster in the constellation Coma Berenices

NGC 4147 is the New General Catalogue identifier for a globular cluster of stars in the northern constellation of Coma Berenices. It was discovered by English astronomer William Herschel on March 14, 1784, who described it as "very bright, pretty large, gradually brighter in the middle". With an apparent visual magnitude of 10.7, it is located around 60,000 light years away from the Sun at a relatively high galactic latitude of 77.2°.

NGC 5053 Globular cluster in the constellation Coma Berenices

NGC 5053 is the New General Catalogue designation for a globular cluster in the northern constellation of Coma Berenices. It was discovered by German-British astronomer William Herschel on March 14, 1784 and cataloged as VI-7. In his abbreviated notation, he described it as, "an extremely faint cluster of extremely small stars with resolvable nebula 8 or 10′ diameter, verified by a power of 240, beyond doubt". Danish-Irish astronomer John Louis Emil Dreyer reported in 1888 that the cluster appeared, "very faint, pretty large, irregular round shape, growing very gradually brighter at the middle".

NGC 3256 interacting galaxy

NGC 3256 is a peculiar galaxy formed from the collision of two separate galaxies in the constellation of Vela. NGC 3256 is located about 100 million light years away and belongs to the Hydra-Centaurus supercluster complex. NGC 3256 provides a nearby template for studying the properties of young star clusters in tidal tails. The system hides a double nucleus and a tangle of dust lanes in the central region. The telltale signs of the collision are two extended luminous tails swirling out from the galaxy. The tails are studded with a particularly high density of star clusters. NGC 3256 is the most luminous galaxy in the infrared spectrum located within z 0.01 from Earth.

NGC 3311 galaxy

NGC 3311 is a supergiant elliptical galaxy located about 190 million light-years away in the constellation Hydra. The galaxy was discovered by astronomer John Herschel on March 30, 1835. NGC 3311 is the brightest member of the Hydra Cluster and forms a pair with NGC 3309 which along with NGC 3311, dominate the central region of the Hydra Cluster.


  1. Ostriker, Jeremiah P.; Spitzer, Lyman, Jr.; Chevalier, Roger A. (September 1972). "On the Evolution of Globular Clusters". Astrophysical Journal . 176: L51. Bibcode:1972ApJ...176L..51O. doi:10.1086/181018.CS1 maint: multiple names: authors list (link)
  2. Lee, Hyung Mok (March 12–16, 2001). "The Life and Death of Globular Clusters". Written at Pucon, Chile. In D. Geisler; E.K. Grebel; D. Minniti (eds.). Extragalactic Star Clusters, IAU Symposium 207. San Francisco: Astronomical Society of the Pacific (published 2002). Bibcode:2002IAUS..207..584L.
  3. Zou, Hu; Wu, Zhen-Yu; Ma, Jun; Zhou, Xu (October 2009). "The tidal tails of globular cluster Palomar 5 based on the neural networks method". Research in Astronomy and Astrophysics. 9 (10): 1131–1148. arXiv: 0905.3614 . Bibcode:2009RAA.....9.1131Z. doi:10.1088/1674-4527/9/10/005.
  4. Yim, Ki-Jeong; Lee, Hyung Mok (June 2002). "Tidal Tails of Globular Clusters". Journal of the Korean Astronomical Society. 35 (2): 75–85. Bibcode:2002JKAS...35...75Y. doi:10.5303/jkas.2002.35.2.075.