Nature vs. Nurture Debate is Universal

The 3-D distribution of galaxies in a slice of the universe as it was 7 billion years ago, based on the new study. Brighter areas represent the regions of the Universe with most galaxies. Astonishingly, the galaxy distribution (the building blocks of the large scale structure) takes the shape of a helix at this primordial epoch. CREDIT: ESO/VLT/VVDS

The question of "nature vs. nurture" applies to more than just child development. Astronomers have long tried to answer this same question about galactic evolution. And according to a recent study, environment may be an important factor in shaping a galaxy's properties over time.

At the beginning of the 20th century, Edwin Hubble realized that galaxies today are not randomly distributed. Old, red elliptical galaxies, which have no or few new stars, tend to be found in clusters, whereas young, blue spiral galaxies, where stars are still forming, tend to have fewer neighbors.

Astronomers theorized that either this had always been the case in the universe, or some influence of the surrounding environment must have changed the distribution and shape of galaxies over time.

A team of astronomers investigated this conundrum using the European Southern Observatory's Very Large Telescope to build a three-dimensional atlas of the universe going back more than 9 billion years. They studied more than 6,500 galaxies to see how their properties varied over different timescales.

"We discovered that, when the universe was younger, this segregation between galaxies' form and environment did not exist," astronomer Christian Marinoni of the Laboratoire d'Astrophysique de Marseille, France told LiveScience.

Their research showed that both elliptical and spiral galaxies were found in different environments, which suggests that the shape of galaxies is affected by some physical mechanism that has acted over nearly the whole life of the universe.

"This is the smoking gun we were looking for," Marinoni said.

The team's findings suggest if a galaxy is located in a cluster, its ability to form new stars is quenched more quickly than galaxies located in sparser areas. Simulations agree with these findings--according to Marinoni the gas in clusters become too hot to cool down and collapse to form new stars.

More luminous galaxies also exhaust their star-forming material more quickly.

"Our results indicate that environment is a key player in galaxy evolution, but there's no simple answer to the 'nature versus nurture' problem in galaxy evolution," said astronomer Olivier Le F?vre. "They suggest that galaxies as we see them today are the product of their inherent genetic information, evolved over time, as well as complex interactions with their environments."

This article is part of SPACE.com's weekly Mystery Monday series.

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