Bina Collaboration

BINA COLLABORATION

Prof Rajesh Dubey was invited for his lecture in Galaxy Collisions in Royal Observatory, Brussels, Belgium under BINA collaboration which is a Belgo-Indian Network of Astronomy and Astrophysics, between government of India and Belgium.

Lecture on Galaxy Collisions

Galaxy collision is an important event in astrophysics and opens doors for many unanswered questions. The collision between NGC 1232 with a dwarf galaxy or NGC 5256 is another example of merging of two galaxies. APR 256 is another example of merging of the two spiral galaxies. These collisions takes place for millions of years and the statistics changes with time. However, observations show that these events may result in very high temperatures of the order of a few MK, covers and spread over very large areas of the order of few kpc in diameter, and moderate to high luminosity. Depending upon certain factors the collision can be observed under X-RAY band or gamma ray bands. By studying these collisions, the prediction can be made about the shape, size, temperature, expansion, luminous afterglow, etc. of the resulting galaxy. For example, two spiral galaxies can merge to form an elliptical galaxy. The behaviour of present such events can help in predicting the future events.

What is Galactic Evolution?

On a clear night, you can make out the band of the Milky Way in the night sky. For millennia, astronomers looked upon it in awe, slowly coming to the realization that our Sun was merely one of billions of stars in the galaxy. Over time, as our instruments and methods improved, we came to realize that the Milky Way itself was merely one of billions of galaxies that make up the Universe.

Thanks to the discovery of Relativity and the speed of light, we have also come to understand that when we look through space, we are also looking back in time. By seeing an object 1 billion light-years away, we are also seeing how that object looked 1 billion years ago. This “time machine” effect has allowed astronomers to study how galaxies came to be (i.e. galactic evolution). The process in which galaxies form and evolve is characterized by steady growth over time, which began shortly after the Big Bang. This process, and the eventual fate of galaxies, remain the subject of intense fascination, and is still fraught with its share of mysteries.