Astronomers can use telescopes to find specific molecules in the atmospheres of neighboring planets, in nebulae – clouds of interstellar dust and gas – hundreds or thousands of light-years away, or in galaxies beyond the far reaches of the Milky Way.
So far, astronomers have found more than 350 molecules in the spaces between and around stars in just under a hundred years – the first such molecule was reported in 1937. Each year, the cosmic chemical stockroom grows by anywhere from a handful to a couple of dozen new finds. Many of these molecules are precursors to biomolecules, meaning they might provide hints about life’s origins elsewhere in the cosmos.
As an astrochemist, my research is all about chemicals found in space, especially in distant cosmic clouds where infant stars are born. Even so, the precise observations captured by these telescopes never cease to amaze me.
With this ongoing boom in astrochemical census data, there is a lot to be excited about. Sometimes, however, this excitement can be premature. Finding molecules in places people will likely never visit is no simple task, so vetting and sometimes correcting these observations is a continual process – especially for molecules whose signals aren’t as strong.
‘Seeing’ molecules in space
Astronomers can’t visit neighboring planets, let alone distant star-forming regions. So, how do they see what is out there?
Astronomers observe the cosmos with telescopes that collect all different wavelengths of electromagnetic energy. For astrochemistry, they typically use radio telescopes. These satellite-dishlike instruments are used to “see” radio waves, which have wavelengths much longer than the human eye can perceive.
The Robert C. Byrd Green Bank Telescope in West Virginia is a radio telescope that has been used in the discovery of many astromolecules.
NSF/AUI/NRAO/John Stoke, CC BY
When molecules freely tumble around as gases in space, they rotate, and this motion releases energy in the form of photons, or electromagnetic particles. Different types of rotations require different levels of energy. Each photon carries that energy with it to a telescope, which records its signal. The more photons of a given energy, the stronger that signal.
If a radio telescope records all of the expected signals for a given molecule – its spectrum – then astronomers can confidently say that they have detected that molecule.
Infrared telescopes, such as the James Webb Space Telescope, or telescopes that detect visible light, such as the Hubble Space Telescope, can also be used for astrochemistry. Both kinds of telescopes, however, collect chemical signals, which are often more difficult to distinguish from one another.
Knowing what to look for
Behind every discovery of a new molecule in space is months or even years of work to capture a chemical’s “fingerprints,” or its spectrum.
I spent about a year doing…
