How the Telescope Captured These Images
The Keck telescope used a special instrument called an integral field spectrograph that works like this:
Normal spectrographs split light into a rainbow, telling you which colors (wavelengths) are present. That reveals which chemicals are there because each chemical absorbs or emits specific colors.
An integral field spectrograph does this for hundreds of different points across the comet simultaneously. It’s like taking hundreds of rainbow measurements at once, each from a slightly different location. When you combine all that data, you get a 3D map: chemical composition in two dimensions of space, plus wavelength.
The August observation covered an area of space about 3,500 miles across—roughly the width of the continental United States—centered on the object. The telescope collected light for 15 minutes, building up enough signal to detect even faint emission from gases.
To isolate the light from the gases themselves, scientists had to subtract the sunlight reflecting off 3I/ATLAS’ icy surface. They did this by observing a normal star that has the same color as the Sun, then using that as a reference to subtract the reflected light, leaving only the glow from excited gas molecules.
