Question

Explain how astronomers are able to tell which elements are present in distant stars by analyzing the electromagnetic radiation emitted by the stars.

Short answer

Astronomers are able to identify elements in distant stars by analyzing their emitted electromagnetic radiation and identifying the unique spectral lines corresponding to different elements.

Step-by-step solution

Understanding Electromagnetic Radiation

Every star, including the Sun, emits electromagnetic radiation across a broad spectrum. The most familiar part of this spectrum is the visible light that we can see with our naked eyes. This light can be broken down into a range of wavelengths (or colors) by a process called diffraction, similar to how a prism splits white light into a rainbow.

Understanding Spectral Lines

When this diffraction is done on a more detailed scale, it results in a pattern of dark lines appearing at specific wavelengths within the spectrum, these are called spectral lines. Every element, when heated to incandescence, emits light of specific energies (or equivalently, specific wavelengths). These 'emission lines' are unique to each element, almost like fingerprints.

Identifying Elements in Stars

When astronomers analyze the light coming from a distant star, they break it down into its spectrum and look for these emission lines. If an element is present in the star, then its unique spectral line will show up in the spectrum of the star's light. The relative intensities of the spectrum lines can even tell them about the relative abundances of the different elements.