What astronomers really found in the Sagittarius B2 cloud, how molecular spectroscopy reveals it, and why the result matters for astrochemistry.
No, you cannot literally smell the Milky Way, and space does not carry aromas the way air does on Earth. The claim comes from a 2009 radio astronomy result showing that the giant molecular cloud Sagittarius B2 near the Galactic Center contains ethyl formate, a molecule associated with raspberry flavor and a faint rum scent on Earth. So, does the Milky Way smell like raspberries and rum? Metaphorically, yes for that cloud’s chemistry, but practically no because concentrations are tiny and there is no air to transport smells.
Does the Milky Way smell like raspberries and rum?
The idea traces to detections of ethyl formate in Sagittarius B2, a star forming cloud rich in complex organics. On Earth, ethyl formate contributes to the taste of raspberries and the aroma of some rums. In space, identifying this molecule tells us about chemistry, not sensory experience. Even inside dense clouds, the gas is an extreme vacuum by terrestrial standards, and you cannot safely inhale it.
In 2009, astronomers reported ethyl formate and the related molecule n-propyl cyanide in Sagittarius B2 by matching their radio spectral fingerprints, a result covered by Chemistry World based on peer reviewed work.
What did astronomers find in Sagittarius B2?
Sagittarius B2 is one of the Milky Way’s largest molecular clouds, located near the Galactic Center. Using sensitive radio telescopes, teams carried out wide frequency scans and identified specific sets of emission lines from complex molecules. Among them were ethyl formate and n-propyl cyanide, indicating that multi step organic chemistry is active in interstellar ices and gas in this region (Chemistry World).
This discovery built on earlier detections of prebiotic species in the same environment, such as amino acetonitrile in 2008, a key precursor to the simplest amino acid glycine. Later work even found a branched carbon molecule, iso propyl cyanide, in 2014, showing that interstellar chemistry can form complex, biologically relevant backbones.
How does molecular spectroscopy reveal these molecules?
Molecular spectroscopy in the radio and millimeter bands reads the rotational energy transitions of molecules. Each molecule has a unique set of allowed rotations, which appear as a barcode like pattern of lines at precise frequencies. Astronomers record spectra from a cloud, then compare the pattern against laboratory databases to identify molecules and estimate abundances.
Radio telescopes detect molecules by their rotational emission lines in the millimeter and submillimeter range, a standard technique explained by the National Radio Astronomy Observatory’s overview of molecules in space.
Because many lines can blend in crowded spectra, robust identifications require matching many transitions, verifying line strengths, ruling out overlaps, and often confirming with multiple telescopes or follow up observations.
Can humans actually smell space?
No. Smell requires a sufficient number of molecules reaching receptors in your nose, carried by air. Interstellar clouds are far too diffuse, and space is a vacuum.
Typical molecular cloud densities are about 102 to 106 molecules per cubic centimeter, compared to roughly 2.5 × 1019 molecules per cubic centimeter in Earth’s air (Cool Cosmos, Caltech/IPAC).
Astronauts do report a distinct odor on spacesuits after spacewalks, often described as metallic, ozone like or “seared steak.” That scent arises from reactions of atomic oxygen and other species on suit surfaces that are then brought inside a pressurized cabin, not from freely sniffing space (Smithsonian Magazine).
Why is this important for astrochemistry and the origins of life?
Astrochemistry connects interstellar molecules to planet formation and prebiotic chemistry. Finding ethyl formate and other complex organics shows that dust grain ices and gas phase reactions can assemble sizable molecules before planets form. Notable milestones include:
- Amino acetonitrile in Sagittarius B2, a glycine precursor.
- Iso propyl cyanide with a branched carbon skeleton, demonstrating structural complexity in the interstellar medium.
- Ethanolamine, a building block of cell membrane lipids, detected toward a Galactic Center cloud in 2021.
- Glycine in the coma of comet 67P by ESA’s Rosetta mission, showing delivery pathways to young planets.
Together, these results support the idea that young planetary systems can inherit a stock of organic compounds, potentially shortening the path from chemistry to biology.
What are the limitations and what comes next?
Media summaries about tastes and smells can oversimplify. Spectral line confusion in rich sources like Sagittarius B2 makes identifications challenging, laboratory reference data are essential, and abundances are usually tiny. While some amino acids remain unconfirmed in the interstellar medium, higher sensitivity and resolution from facilities such as ALMA and NOEMA are enabling cleaner detections and mapping chemistry across star forming regions, protoplanetary disks, and comets.