Veins are the blood vessels that have thin walls and contain valves.
Veins are blood vessels, and an essential part of the circulatory system that mainly functions by transporting deoxygenated blood back to the heart after arteries transports blood out. Most veins have valves in them to avoid backflow, and their walls are very thinner than that of arteries. The biggest vein in the body is the vena cava. Veins are grouped into; systemic veins, superficial veins, deep veins, pulmonary veins, and communicating veins.
This is false. Absolute brightness is the term used to describe how bright a star would look if it were a standard distance from Earth. Apparent brightness is how bright it would look as far as it currently is from Earth. Hope this was helpful!
