Organic Chemicals That May be the Origins of Life Discovered in Large Magellanic Cloud

The Large Magellanic Cloud is a nearby galaxy and a satellite of the Milky Way. Now, though, scientists have learned a bit more about the LMC. They've found it's made up of a group of organic chemicals that are considered to be carcinogens and pollutants on Earth, but could also be the building blocks of the origins of life.

In this case, the researchers examined how polycyclic aromatic hydrocarbons (PAHs) are created in an aging populations of stars in the LMC. More specifically, they found that the types of PAH found in the atmospheres in these stars are far more varied than the PAHs in our own galaxy.

The researchers examined 24 stars by using the Spitzer Space Telescope. They then analyzed the light from these stars to find features linked to PAHs. Stars are powered by nuclear fusion in their cores, converting hydrogen into helium. Yet toward the end of their lives once they consume all of their hydrogen, they begin to convert helium to oxygen and carbon. In this case, the researchers focused their studies on stars that appeared to be in the process of fusing carbon.

"We were surprised because previous measurements of PAHs in interstellar dust in the Large Magellanic Cloud were very similar to those in the Milky Way," said Mikako Matsuura, one of the researchers, in a news release. "Our studies suggest that these organic molecules are processed and change their composition soon after they are ejected by dying stars to fill the matter within the galaxy. Dying stars in the neighboring galaxy are richer in carbon than the Milky Way's stars, so are more likely to trigger these wide varieties of organic compounds."

The findings reveal a bit more about the LMC. More specifically, it tells a bit more about stellar evolution.

"We think that, as the central star evolves, the increasingly energetic radiation affects the compositions of the PAHs, leading to more varieties," said Matsuura. "However, once the PAHs are mixed into the interstellar medium, this variability decreases. One possibility for this contrast is that ultraviolet radiation might change the profiles of the PAHs. Another is that PAHs are re-processed further in the interstellar medium, changing their composition."

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.