Final answer:
Astronomers use spectroscopy to identify elements in a nebula; for instance, the Crab Nebula contains sulfur and double-ionized oxygen ions. Emission nebulae are rich in hydrogen, causing a red glow, whereas absorption lines in interstellar space reveal elements like calcium and sodium. Additionally, cosmic rays suggest that lithium, beryllium, and boron are present in higher amounts compared to stars.
Step-by-step explanation:
When it comes to identifying the elements contained within a nebula, astronomers use the science of spectroscopy. By measuring the light wavelengths emitted from a nebula, they can determine the presence of various ions and elements. For instance, the Crab Nebula's composite image taken by NASA's Hubble Space Telescope reveals the presence of ions such as S+ (sulfur ions) manifesting in green filaments and O²+ (double-ionized oxygen) appearing in red filaments.
Aside from sulfur and oxygen, other elements can be detected in nebulas. Neutral hydrogen, for example, does not emit light in the visible spectrum, yet it is a major component of emission nebulae. These nebulae also show the first line in the Balmer series, which is an indication that hydrogen is present. Emission nebulae are also marked by their distinctive red glow due to hydrogen emission.
In absorption nebulae, the interstellar dust may absorb and scatter light, revealing the predominance of elements like hydrogen. When bright sources such as stars or galaxies are observed through interstellar space, various absorption lines are detected, attributed to elements including calcium and sodium, among others. Cosmic rays also provide clues to the elemental composition since they contain nuclei reflecting the abundances in stars and interstellar gas. Notably, elements like lithium, beryllium, and boron are more abundant in cosmic rays than in stars, formed by collisions involving heavier cosmic-ray nuclei.
In summary, various elements make up the complex tapestry of a nebula, identified by the light they emit or absorb, witnessed by the beautiful images and spectra captured by telescopes like Hubble.