Galactic tides

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Galactic tides are tidal forces that act on objects in the gravitational field of a galaxy . These include, for example, interactions between galaxies or the influence of the Milky Way on the Oort cloud of the solar system .

Emergence

Galactic tides have the same cause as the tides on Earth. However, they are characterized by much larger intervals and times. Galaxies can be stretched, flattened or completely or partially torn apart by tidal forces and their orbit can be disturbed. Rapidly rotating galaxies are particularly strongly deformed as a result.

Effects

Collision of galaxies

The significant effect of galactic tidal forces is limited to the immediate vicinity of galaxies. However, when two large galaxies collide, tidal forces can create extreme interactions between galaxies . Mergers of galaxies take several hundred million years, the calming processes even longer.

Collision of galaxies: NGC 4676 (sometimes the Mice dt. , The mice called)

Interaction with satellite galaxies

Since satellite galaxies are in the immediate vicinity of a large galaxy, they are usually particularly badly affected by galactic tidal forces.

For example, it is believed that M32 , a satellite galaxy in the Andromeda Nebula , lost its spiral arms due to galactic tidal action. At the same time, star formation in this galaxy has been intensified.

Interactions within galaxies

Galactic tides also operate within a galaxy. However, this effect is usually only significant in the outer regions of a planetary system , because there the gravity of the central star is weaker. In the solar system, the galactic tides have an impact on the Oort cloud. It is assumed that objects in the Oort cloud are thrown out of their orbit and enter the inner solar system as comets .

Galactic Outflow

New research shows that massive galactic molecular outflows can have the physical conditions, such as high gas densities, to form stars. This mode of star formation is remarkable as it could contribute to the morphological evolution of galaxies.

Remarks

  1. ↑ Bekki, Kenji; Couch, Warrick J .; Drinkwater, Michael J .; Gregg, Michael D .: A New Formation Model for M32: A Threshed Early-Type Spiral Galaxy? . In: The Astrophysical Journal . 557, 2001, S. Issue 1, pp. L39-L42. bibcode : 2001ApJ ... 557L..39B . doi : 10.1086 / 323075 .
  2. ^ R. Maiolino et al: Star formation inside a galactic outflow. In: Nature.com. 2017.

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