Tidal tail

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The Tadpole Galaxy UGC 10214HST.jpg
The Tadpole Galaxy

A tidal tail is a thin, elongated region of stars and interstellar gas that extends into space from a galaxy. Tidal tails occur as a result of galactic tide forces between interacting galaxies. Examples of galaxies with tidal tails include the Tadpole Galaxy and the Mice Galaxies. Tidal forces can eject a significant amount of a galaxy's gas into the tail; within the Antennae Galaxies, for example, nearly half of the observed gaseous matter is found within the tail structures. [1] Within those galaxies which have tidal tails, approximately 10% of the galaxy's stellar formation takes place in the tail. [2] Overall, roughly 1% of all stellar formation in the known universe occurs within tidal tails. [3]

Star sphere of plasma held together by gravity, undergoing fusion; type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity

A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the estimated 300 sextillion (3×1023) stars in the Universe are invisible to the naked eye from Earth, including all stars outside our galaxy, the Milky Way.

Galaxy astronomical structure

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million stars to giants with one hundred trillion stars, each orbiting its galaxy's center of mass.

Galactic tide Tidal force experienced by objects subject to the gravitational field of a galaxy

A galactic tide is a tidal force experienced by objects subject to the gravitational field of a galaxy such as the Milky Way. Particular areas of interest concerning galactic tides include galactic collisions, the disruption of dwarf or satellite galaxies, and the Milky Way's tidal effect on the Oort cloud of the Solar System.


Some interacting galaxy pairs have two distinct tails, as is the case for the Antennae Galaxies, while other systems have only one tail. Most tidal tails are slightly curved due to the rotation of the host galaxies. Those that are straight may actually be curved but still appear to be straight if they are being viewed edge-on.


The phenomena now referred to as tidal tails were first studied extensively by Fritz Zwicky in 1953. [4] Several astrophysicists expressed their doubts that these extensions could occur solely as the result of tidal forces, [5] [6] including Zwicky himself, who described his own views as "unorthodox". [7] Boris Vorontsov-Velyaminov argued that the tails were too thin and too long (sometimes as large as 100,000 parsecs) to have been produced by gravity alone, [8] as gravity should instead produce broad distortions. However, in 1972, renowned astronomer Alar Toomre proved that it was indeed tidal forces that were responsible for the tails. [9]

Fritz Zwicky Swiss astronomer

Fritz Zwicky was a Swiss astronomer. He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy. In 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen dark matter, describing it as "dunkle Materie".

Boris Vorontsov-Velyaminov Soviet astrophysicist

Boris Aleksandrovich Vorontsov-Velyaminov was a Soviet/Russian astrophysicist. His name is sometimes given as Vorontsov-Vel'yaminov.

Parsec unit of length used in astronomy

The parsec is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond, which corresponds to 648000/π astronomical units. One parsec is equal to about 3.26 light-years. The nearest star, Proxima Centauri, is about 1.3 parsecs from the Sun. Most of the stars visible to the unaided eye in the night sky are within 500 parsecs of the Sun.


  1. Mihos, Christopher J.; et al. (1993). "Modeling the Spatial Distribution of Star Formation in Interacting Disk Galaxies". Astrophysical Journal. 418: 82–99. Bibcode:1993ApJ...418...82M. doi:10.1086/173373.
  2. Jarrett, T. H.; et al. (2006). "Remarkable Disk and Off-Nuclear Starburst Activity in the Tadpole Galaxy as revealed by the Spitzer Space Telescope". Astronomical Journal. 131 (1): 261–281. arXiv: astro-ph/0510788 . Bibcode:2006AJ....131..261J. doi:10.1086/498414.
  3. Naeye, Robert (18 December 2007). "'Shot in the Dark' Star Explosion Stuns Astronomers". NASA Goddard Flight Center. Retrieved 18 June 2010.
  4. Zwicky, Fritz (April 1953). "Luminous and dark formations of intergalactic matter". Physics Today . 6 (4): 7–11. Bibcode:1953PhT.....6....7Z. doi:10.1063/1.3061224.
  5. Zasov, A. V. (1968). "The Possibility of a Long Lifetime for Intergalactic Arms". Soviet Astronomy. 11 (5): 785. Bibcode:1968SvA....11..785Z.
  6. Gold, T. & Hoyle, F. (1959). "Cosmic rays and radio waves as manifestations of a hot universe". Paris Symposium on Radio Astronomy. Stanford University Press. pp. 583–588.
  7. Zwicky, Fritz (1963). "Intergalactic Bridges". Astronomical Society of the Pacific Leaflets. 9 (403): 17–24. Bibcode:1963ASPL....9...17Z.
  8. Vorontsov-Velyaminov, B. (1962). "Interaction of Multiple Systems". Problems of Extra-Galactic Research. Macmillan Press. pp. 194–200. Bibcode:1962IAUS...15..194V.
  9. Toomre, Alan & Toomre, Juri (15 December 1972). "Galactic Bridges and Tails". Astrophysical Journal. 178: 623–666. Bibcode:1972ApJ...178..623T. doi:10.1086/151823.
  10. "Hubble detects supermassive black hole kicked out of galactic core - Astronomers suspect gravitational waves". www.spacetelescope.org. Retrieved 27 March 2017.

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