This image of the Triangulum galaxy, or M33, includes data from the ESA (European Space Agency) Herschel mission, supplemented with data from ESA's retired Planck observatory and two retired NASA missions: the Infrared Astronomical Satellite (IRAS) and Cosmic Background Explorer (COBE).

Operated from 2009 to 2013, Herschel detected wavelengths of light in the far-infrared and microwave ranges, and was ideal for studying dust in nearby galaxies because it could capture small-scale structures in the dust clouds in high resolution. However, Herschel often couldn't detect light from diffuse dust clouds – especially in the outer regions of galaxies, where the gas and dust become sparse and thus fainter. As a result, the mission missed up to 30% of all the light given off by dust. Combining the Herschel observations with data from other observatories creates a more complete picture of the dust in the galaxy.

In the image, red indicates hydrogen gas; green indicates cold dust; and warmer dust is shown in blue. Launched in 1983, IRAS was the first space telescope to detect infrared light, setting the stage for future observatories like NASA's Spitzer Space Telescope and James Webb Space Telescope. The Planck observatory, launched in 2009, and COBE, launched in 1989, both studied the cosmic microwave background, or light left over from the big bang.

The hydrogen gas was detected using the Green Bank Telescope in West Virginia, the Karl G. Jansky Very Large Array in New Mexico, and the Institute for Radio Astronomy in the Millimeter Range 30-meter telescope in Spain.