Today I celebrate 63 successful orbits of this yellow-dwarf star we call Sol¹.

Yet all is not as it seems. At the completion of one orbit, I never really come back to the same place. The sun has moved along on its own orbit around the galactic centre (at a brisk 230 kilometres per second).

In reality, after completing one orbit of the sun, I will now be about 7.26 billion kilometres away from my starting point.

You want to know how long it will take for me to return to that same point? Well, crunching the numbers I calculate (ie I look it up on wikipedia) roughly 250 million years².

Cosmologists have calculated that our Sol was ‘born’ on May 9th. What a coincidence! Not many people know that³.

Over its own lifetime, Sol has completed (approx) 20 orbits of the galactic centre (one galactic year).
So happy 20th for the sun too!

Therefore, I celebrate that I am 63 Sol years and 0.00000028 Galactic years old today.

To mark this occasion with its due significance, I shall be going out to a swish Japanese restaurant. Here I will eat sushi and toast with a fine beer for me and a second for the sun⁴.

1. Latin sol “the sun, sunlight” ↩︎
2. Interestingly the sun does not really move much further towards, or away from the galactic centre over one revolution. So at the end of a galactic year we are pretty much back where we started. That surprised me. ↩︎
3. Probably because it is a totally made up fact. ↩︎
4. Also interestingly, since Christmas day I have only had one beer. No other alcohol. But birthdays are worthy of a brew or two…no? ↩︎