This is the expected blackbody spectrum of the starburst galaxy Arp 220 as the object is moved to higher redshift.
Blackbody radiation is the type of radiation emitted by a purely thermal source.
Redshift is the lengthening of the wavelength of light caused by the galaxy's recession from the Earth. As the velocity increases, the color changes from blue to red, hence the term redshift. This phenomenon results from the Doppler effect. The shaded area indicates the frequency range of the Atacama Large Millimeter Array. From this, we can calculate an inferred distance.