Some pairs are optical doubles
They look close but it's just illusion
And some are visual
Claiming roles of primary and secondary
Easy to distinguish
Some pairs are eclipsing
Struggling to outdo the other
To take the front, to claim the glory
The worst are astrometric
One always in shadow
Hidden, invisible, unseen
But you and me?
We're double lined spectroscopic
Our orbits fast and close
And only those who know us best
Know there's a difference at all