American charges for checked bags; Southwest lets you check two bags for free as long as they don't weigh over 50 pounds; JetBlue gives you the first checked bag free; and only Spirit also charges for carry on bags unless they're small enough to fit under the seat in front of you.
Remnant definition, a remaining, usually small part, quantity, number, or the like. See more.
An explosion of that magnitude doesn't simply dissipate in a short amount of time (at least not by human standards). A supernova remnant is simply the expanding blast wave from the explosion plowing through outer space, as well as the remains of what was once the star following behind it.