Planets in Other Galaxies

Feb 15, 2018

Dr. Todd Young revisits last week topic about the stars and planets and adds some final thoughts.

Recently in the news there was an announcement that astronomers had discovered planets orbiting stars in other galaxies.  This is both expected and amazing at the same time.  Last week we discussed how it was expected because it is part of the star formation process that planets also form around the star.  What is amazing about this discovery is how it was discovered. 

Astronomers using the Chandra X-ray telescope were studying a super-massive black hole at the center of a galaxy about 4 billion light-years away.  Now put this distance in some sort of perspective, that means it takes 4 billion years for light from that galaxy to travel to Earth and the distance is about 100 billion times 100 billion miles! During their research, the light from this distant galaxy traveled around a smaller galaxy closer the Earth but still millions of light-years away. According to Einstein’s general theory of relativity, large mass objects can warp the space around it; this is how the light from a distant galaxy can bend and travel “around” a closer galaxy.  And when this happens, the closer galaxy acts like a magnifying glass in a phenomenon called “gravitational lensing.”  It was with this gravitational lensing and careful analysis of the light that they discovered upwards of a trillion planets existing in the closer galaxy!  And according to the cosmological principle which states that the laws of physics are same everywhere in the universe, this means that we have an implicit conformation that every galaxy must have billions upon trillion of planets!

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Follow your curiosity to the Fred G. Dale Planetarium at Wayne State College.