Respuesta :

because radiation goes a long way. Radiation itself isn't visable but if it's from a nearby star you'll be able to see the star. Radiation keeps moving outwards forever. Things that can sense radiation that you can't see will help you have an idea how far away the source of that radiation is from
keontehamilton1
because some objects emit radiation that only an x-ray telescope would show,something that an optical one wouldn't pick up in space