Editing Globular cluster (section)

==Tidal encounters==
When a globular cluster comes close to a large mass, such as the core region of a galaxy, it undergoes a [[Tidal force|tidal interaction]]. The difference in gravitational strength between the nearer and further parts of the cluster results in an asymmetric, tidal force. A "tidal shock" occurs whenever the orbit of a cluster takes it through the plane of a galaxy.<ref name=apj522_2_935/><ref name=aj176_L51>{{cite journal |last1=Ostriker |first1=Jeremiah P. |last2=Spitzer |first2=Lyman Jr. |last3=Chevalier |first3=Roger A. |date=September 1972 |title=On the Evolution of Globular Clusters |journal=[[Astrophysical Journal]]  |doi=10.1086/181018 |bibcode=1972ApJ...176L..51O |volume=176 |page=L51}}</ref>

Tidal shocks can pull stars away from the cluster halo, leaving only the core part of the cluster; these trails of stars can extend several degrees away from the cluster.<ref>{{cite conference |last1=Lauchner |first1=A. |last2=Wilhelm |first2=R. |last3=Beers |first3=T. C. |last4=Allende Prieto |first4=C. |date=December 2003 |title=A Search for Kinematic Evidence of Tidal Tails in Globular Clusters |work=American Astronomical Society Meeting 203, #112.26 |bibcode=2003AAS...20311226L}}</ref> These tails typically both precede and follow the cluster along its orbit and can accumulate significant portions of the original mass of the cluster, forming clump-like features.<ref>{{cite conference |last1=Di Matteo |first1=P. |last2=Miocchi |first2=P. |last3=Capuzzo Dolcetta |first3=R. |date=May 2004 |title=Formation and Evolution of Clumpy Tidal Tails in Globular Clusters |work=American Astronomical Society, DDA meeting #35, #03.03 |bibcode=2004DDA....35.0303D |url=https://www.researchgate.net/publication/1799679}}</ref> The globular cluster [[Palomar 5]], for example, is near the [[Apsis|apogalactic point]] of its orbit after passing through the Milky Way. Streams of stars extend outward toward the front and rear of the orbital path of this cluster, stretching to distances of 13,000 light years. Tidal interactions have stripped away much of Palomar{{spaces}}5's mass; further interactions with the galactic core are expected to transform it into a long stream of stars orbiting the Milky Way in its halo.<ref>{{cite press release
 | last=Staude
 | first=Jakob
 | date=June 3, 2002
| url=http://classic.sdss.org/news/releases/20020603.pal5.html
 | title=Sky Survey Unveils Star Cluster Shredded By The Milky Way
 | work=Image of the Week
 | publisher=Sloan Digital Sky Survey
 | access-date=April 9, 2021
| archive-url=https://web.archive.org/web/20060629091731/http://www.sdss.org/news/releases/20020603.pal5.html
 | archive-date=June 29, 2006
| url-status=live
 }}</ref>

The Milky Way is in the process of tidally stripping the [[Sagittarius Dwarf Spheroidal Galaxy]] of stars and globular clusters through the [[Sagittarius Stream]]. As many as 20% of the globular clusters in the Milky Way's outer halo may have originated in that galaxy.<ref>{{cite journal |last1=Carballo-Bello |first1=J. A. |last2=Corral-Santana |first2=J. M. |last3=Martínez-Delgado |first3=D. |last4=Sollima |first4=A. |last5=Muñoz |first5=R. R. |last6=Côté |first6=P. |last7=Duffau |first7=S. |last8=Catelan |first8=M. |last9=Grebel |first9=E. K. |title=The southern leading and trailing wraps of the Sagittarius tidal stream around the globular cluster Whiting 1 |journal=Monthly Notices of the Royal Astronomical Society: Letters |date=January 24, 2017 |volume=467 |issue=1 |pages=L91–L94 |doi=10.1093/mnrasl/slx006 |doi-access=free |bibcode=2017MNRAS.467L..91C |arxiv=1612.08745}}</ref> [[Palomar 12]], for example, most likely originated in the Sagittarius Dwarf Spheroidal but is now associated with the Milky Way.<ref>{{cite journal
 |author1=Dinescu, D. I. |author2=Majewski, S. R. |author3=Girard, T. M. |author4=Cudworth, K. M. | title=The Absolute Proper Motion of Palomar 12: A Case for Tidal Capture from the Sagittarius Dwarf Spheroidal Galaxy
 | journal=[[The Astronomical Journal]] | date=2000
 | volume=120 | issue=4 | pages=1892–1905
 | bibcode=2000AJ....120.1892D
 | doi=10.1086/301552 |arxiv = astro-ph/0006314 |s2cid=118898193 }}</ref><ref>{{cite journal |last1=Sbordone |first1=L. |last2=Bonifacio |first2=P. |last3=Buonanno |first3=R. |last4=Marconi |first4=G. |last5=Monaco |first5=L. |last6=Zaggia |first6=S. |title=The exotic chemical composition of the Sagittarius dwarf spheroidal galaxy |journal=Astronomy & Astrophysics |date=April 2007 |volume=465 |issue=3 |pages=815–824 |doi=10.1051/0004-6361:20066385|arxiv=astro-ph/0612125 |bibcode=2007A&A...465..815S |doi-access=free }}</ref> Tidal interactions like these add kinetic energy into a globular cluster, dramatically increasing the evaporation rate and shrinking the size of the cluster.<ref name="structure" /> The increased evaporation accelerates the process of core collapse.<ref name="structure" /><ref>{{cite journal |last1=Gnedin |first1=Oleg Y. |last2=Ostriker |first2=Jeremiah P. |title=Destruction of the Galactic Globular Cluster System |journal=The Astrophysical Journal |date=January 1997 |volume=474 |issue=1 |pages=223–255 |doi=10.1086/303441|arxiv=astro-ph/9603042 |bibcode=1997ApJ...474..223G |doi-access=free }}</ref>