Infrared wavelengths of 3.6, 8.0, and 24 µm are mapped into visible colors red, green, and blue in this Spitzer Space Telescope image. The cloud of gas and dust is W33, a massive starforming complex some 13,000 light-years distant near the plane of our Milky Way Galaxy.
Amateur scientists of the web-based Milky Way Project found the features they called yellow balls as they scanned many Spitzer images and persistently asked that question of the pros. Now there is an answer. The yellow balls are an early stage of massive star formation. They appear yellow in the false color IR images because they are overlapping regions of “red” and “green,” the colors that correspond to dust and organic molecules known as PAHs at the Spitzer detector wavelengths. Yellow balls represent the stage before newborn massive stars clear out cavities in their surrounding gas and dust.
Image Credit: NASA