Some 5 billion years ago, the Sun developed from a shell of gas and dust in an interstellar cloud measuring hundreds of light years across. A light year is about ten trillion kilometres in length. Most likely, the shockwave of a nearby exploding star called a supernova sent pockets of this material spinning.
Over time, these pockets condensed and collapsed upon itself and over time, flatten out and widen like pizza dough. Our protostar at the centre began getting hotter and larger with gravity pulling in more gas. This “snowball effect” continued until our Sun grew to its present size of 1.4 million kilometres across or 109 earths lined up side by side like a string of pearls. There were most likely other sibling stars born from that same interstellar cloud so long ago.
Once the Sun reached a critical internal temperature of 15 million degrees Celsius, it lit up by nuclear fusion and the shock wave blew away some of the closer material outwards into the pancake of dust. Over time dust grains began sticking together to produce sand-size particles. Like sticking bits of Play-Doh together, about 100 baby planets called planetesimals came to be. Flying in all directions like a cosmic demolition derby, collisions resulted in utter destruction of the two bodies or the soft merger creating new larger worlds. Our solar system ended up with a family of eight main planets, hundreds of moons, tens of thousands of asteroids and billions of comets.
We refer the Sun as our daytime star and we orbit it at an average distance of 150 million kilometres or one astronomical unit (AU). This is a mere baby step compared to our neighbouring star called Proxima Centauri at 4.3 light-years (ly) away. This star is located in the southern hemisphere and not seen from Canada. We do however see the bright star Sirius at 8.6 ly from us. End-to-end our Milky Way Galaxy measures 100,000 light years across.
The Earth has created some 4.5 billion years ago with simple cell organisms emerging a few million years later. About 3.8 billion years ago, cyanobacteria began forming mostly on stromatolites and began the process of photosynthesis that produced oxygen. The Sun is not only a heat and light source but grows our food and helps our skin produce vitamin D, which is beneficial to our health. Earth is located in the habitable or “Goldilocks Zone” where oceans remain liquid. If our planet were closer or farther from the Sun, water would boil away or freeze.
To date, more than 3,700 exoplanets have been discovered orbiting distance stars with some four thousand possible candidates. A few exoplanets are believed to lie in habitable zone so if that planet has water, life might also be possible. The same 92 natural elements found on the periodic table can be found throughout the entire universe with the recipe for possible life in the making.
Next time you look up at the night sky, you might be gazing upon distant solar systems with a planet and the possibility of life.
Till next time, clear skies.
Known as “The Backyard Astronomer”, Gary Boyle is an astronomy educator, guest speaker and monthly columnist for the Royal Astronomical Society of Canada. He has been interviewed on more than 50 Canadian radio stations and local Ottawa TV. In recognition of his public outreach in astronomy, the International Astronomical Union has honoured him with the naming of Asteroid (22406) Garyboyle. Follow him on Twitter: @astroeducator or his website: www.wondersofastronomy.com