Intergalactic Stars: Countless Isolated Worlds

We often talk about galaxies and the billions of stars they contain. But are there stars that hover endlessly outside its gravitational grip?

Stars are themselves gravity monsters. Our solar system is a good example as all of its content revolves around it. Our star revolves around our Milky Way galaxy and does a revolution approximately every 250 million years.

Does it happen a star escapes the gravity of its original system in which it has formed? How do they go, Rogue?

Intergalactic stars (also known as intracluster stars or rogue stars) are not bound gravitationally to any galaxy

  • these stars have originated in galaxies, like other stars, but later expelled as the result of either colliding galaxies or of a multiple-star system traveling too close to a supermassive black hole, which is found at the center of many galaxies, including our own Sagittarius A (Sgr. A) found at the core of our galaxy approximately 30000 light-years away (see link below more details). It has a combined mass of +/- 4 million stars.
  • Stars that manage to escape the gravity of their host galaxy have to travel at mind-boggling speeds. The Very Large Telescope and Keck Telescope detected stars orbiting Sgr A* at speeds greater than that of any other stars in the galaxyOne star, (designated S2) was calculated to orbit Sgr A* at speeds of over 5,000 kilometers per second at its closest approach!
  • Stars do not always venture on their own. When in groupings, intergalactic stars are referred to as the intracluster stellar population (IC).
  • The hypothesis that stars exist only in galaxies was disproven in 1997 with the discovery of intergalactic stars. The first to be discovered was in the Virgo cluster of galaxies some 60 million light-years away (see link below), where some 1 trillion stars are thought to exist;
  • "These stars are truly intergalactic because they are so isolated their motion is probably governed by the gravitational field of the cluster as a whole, rather than the pull of anyone galaxy," (Harry Ferguson of Space Telescope Science Institute in Baltimore, Maryland).
  • Model calculations (1988) predict the supermassive black hole in the center of our galaxy expels 1 star every 100,000 years on average.
  • Gaia Space Telescope has spotted high-velocity stars between galaxies, perhaps originating from the small/large Magellanic clouds (satellite dwarf galaxies of the Milky Way). In December 2020, Gaia discovered nearly 600 more bringing the total then to about 1000. This includes at least 43 stars that are unbound to the Milky Way with escape probabilities larger than 50%.

The End Notes

Thats all in this article. I hope you liked it. If you have any questions or suggestions on this, kindly post them below. Have a good one. Cheers!

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