Space – The final frontier

Background image credit: NASA/JPL-Caltech

I may continue with the full phrase like “These are the voyages of the Starship, Enterprise …” but we are a long way to say that. Presently we just managed to send people to our moon, some time ago, and we are scratching the surface of our solar system.

This doesn’t mean that we didn’t travel in our Galaxy, on the contrary our very own starship, the Earth, could very well have done a full circle around the Galactic center and traversed four Galactic arms in the last 500 Myr. This is well explained in a very nice article by D. R. Gies and J. W. Helsel from the Georgia State University, Atlanta.

One of the main points of the article is the possible link between the long exposure to cosmic rays of the Earth due to crossing of the Galactic arms and the long ice age epochs on Earth. Another interesting thing is the up and down movement of the path of the Earth on the Galactic plane, our starship travelling around 50 pc from the plane each time.

In total the Sun system made about 20 cycles around the Galaxy, and in that period traversed many times the (possible) four arms of the Galaxy, regions with enhanced star formation and supernova rates that create more intense exposure to cosmic. And this long exposure could influence life formation and evolution in our solar system.

It is difficult to make clear statements about the path of the Earth around the Galaxy because of several reasons, we don’t know the exact number of spiral arms of our Galaxy, the angular rotation speed of the Galactic spiral pattern has large uncertainties and also the Sun’s orbit in the Galaxy is not circular.

Still, using different models for the Galactic gravitational potential and data from the Hipparcos Satellite, the authors made a possible analogy between the path of the Earth in the Galaxy and the recent ice age epochs, matching four periods of extended cold over the last 500 Myr with the Sun’s passages through spiral arms.

This opens the way for future correlation of events recorded in the history of the Earth and our voyage around the Galaxy, “to boldly go where no man has gone before”.