Astronomers have used a survey of the night sky to map the elements of life across the galaxy.

The findings come from the Sloan Digital Sky Survey (SDSS), an international effort to catalog 150,000 stars in the Milky Way. Using the Apache Point Observatory in New Mexico, astronomers were able to measure the abundance of two dozen chemical elements in each star – and this included the building blocks of all life on Earth.

These elements in question are known as the CHNOPS elements – carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur – which make up more than 97 percent of the mass of a human body. To measure the stars, astronomers used a method called spectroscopy, which observes the light of the stars to work out how much of each element they contain.

“For the first time, we can now study the distribution of elements across our Galaxy,” said Sten Hasselquist of New Mexico State University, one of the astronomers in the research, in a statement. “The elements we measure include the atoms that make up 97% of the mass of the human body.”

Heavier elements like oxygen were found to be more abundant in the inner regions of the galaxy, where stars are generally older. It suggests that the requirements for rocky planets, and life itself, have existed much longer towards the center of the Milky Way then in our position in one of the galaxy’s arms. No survey before has been able to map the abundance of elements across the whole galaxy.

^{The dips in the light of a star reveal which elements are present. Dana Berry/SkyWorks Digital Inc/SDSS collaboration}

It’s no secret that stars were responsible for all of the heavier elements in the universe today, lending to the late Carl Sagan’s famous remark that “we are all made of star stuff.” But seeing just how they are spread throughout our galaxy is fascinating indeed.

“It’s a great human interest story that we are now able to map the abundance of all of the major elements found in the human body across hundreds of thousands of stars in our Milky Way,” said Jennifer Johnson of The Ohio State University in the statement. “This allows us to place constraints on when and where in our galaxy life had the required elements to evolve, a sort [of] ‘temporal Galactic habitable zone.’”