TT Cygni is acool redgiant star with a wind.This false-color picture of TT Cyg was made using a coordinated array ofmillimeter wavelength radio telescopes and shows radio emissionfrom carbon monoxide (CO) molecules in the surrounding gas.The central emission is from material blown off thered giantover a few hundred years while the thin ring,with a radius of about 1/4 light-year, actually representsa shell of gas expanding outward for 6,000 years.Carbon stars like TT Cyg are so named for their apparent abundanceof carbon containing molecules.The carbon is likely the dredged-up ashes ofnuclear helium burning in the stellar interior.Carbon stars loose a significant fraction oftheir total mass in the form of astellar windwhich ultimately enriches theinterstellar gas – the source ofmaterial for futuregenerations of stars.TT Cyg is about 1,500 light-years away in theconstellation Cygnus.