The fourth cosmic velocity is the minimum necessary velocity of the body, allowing to overcome the attraction of the galaxy at a given point.
The fourth cosmic velocity is not constant for all points of the galaxy, but depends on the coordinate. It is estimated that in the region of our sun the fourth cosmic velocity is about 550 km / s . The value strongly depends not only (and not so much) on the distance to the center of the Galaxy , but also on the distribution of the masses of matter in the Galaxy, about which there is no exact data, because visible matter makes up only a small part of the total gravitating mass, and everything else is hidden mass . Outside the galactic disk, the mass distribution is approximately spherically symmetric, as follows from measurements of the velocities of globular clusters and other objects of the spherical subsystem.
Calculation
The fourth cosmic velocity is numerically equal to the square root of the gravitational potential φ taken with the opposite sign at a given point in the galaxy (if we select the gravitational potential equal to zero at infinity):
Examples
- The speed of the Sun itself around the center of the Galaxy is approximately 217 km / s, and if it moved about three times faster, then with time it would leave the Milky Way .
- Stars located near a supermassive black hole in the center of our Galaxy ( Sagittarius A * object) can acquire a significant momentum , sometimes sufficient to overcome the attraction of the Galaxy or even much faster, up to speeds of 4000 km / s [1] in some cases.
- Pulsar B1508 + 55 [2] , which is 7700 light-years distant from Earth, moves at a speed of 1100 kilometers per second, which is twice as much as the fourth cosmic velocity in the solar region (550 km / s).
See also
- Space speed
- First cosmic speed
- Second cosmic velocity
- Third space velocity
Notes
- ↑ Ecumenical Catapult: Stars as Shells (Link unavailable) . Popular mechanics (September 14, 2007). Date of treatment November 9, 2011. Archived January 8, 2012.
- ↑ Superfast pulsar about to leave the galaxy
Links
- Zasov A.V., Surdin V.G. Cosmic speeds.