Which tube is next to the descending thoracic aorta

I remember at school there were two tubes in the middle of the torso, one being the descending thoracic aorta, and there was another one. I don't remember if it was the esophagus or trachea. Also, how do I know which is the esophagus and which is the trachea. Thanks!

The trachea is never next to the thoracic aorta, because it ends above it,
by splitting to form the right and left bronchi.
The esophagus is next to the aorta, and travels all the way through the
diaphragm muscle to the stomach.