♦ Each of the many different atoms listed in the
“Periodic Table of the Elements” radiates its own
unique colors when hot.
♦ Study of the spectrum of radiated colors is
the science of spectroscopy.
♦ The colors reveal what chemical elements are present.
See Wikileaks: https://en.wikipedia.org/wiki/Spectroscopy
” Most research telescopes have spectrographs. The measured spectra are used to determine the chemical composition and physical properties of astronomical objects (such as their temperature and velocity).”
Note: The unit “nm” stands for “nanometer”, which is one-billionth of a meter. As used here, for example, 656 nanometers is the “wavelength” of this shade of red light.
More details about the color spectrum at Wikipedia:
https://en.wikipedia.org/wiki/Visible_spectrum
The rainbow color image is also taken from Wikipedia: Attribution: By Gringer –
Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4639774