When it comes to finding a habitable world or a planet with necessary conditions to support life, astronomers mainly look for water, oxygen, or carbon. The three are seen as essential biosignatures, but there is something even more important that scientists have been overlooking so far — phosphorus.

Phosphorus is one of the most crucial ingredients of life as we know it. It is critical for storing and transferring energy, which means living organisms can’t really survive if this element goes missing.

This is why astronomer Jane Greaves from Cardiff University set out to understand how evenly phosphorus is distributed across the cosmos.

Finding the element could be the path to alien life, but it’s not that simple. Phosphorus is extremely rare and is mainly produced from supernovae, the massive explosions in which aged stars eject most of their mass.

Greaves and her colleague Phil Sigan started their work by taking a close look at two different supernova remnants, the left-over rubble from the explosions which is later used for the formation of new planets. They used William Herschel Telescope in the Canary Islands to observe the Crab Nebula, located 6,500 light years away in constellation Taurus and compared that data with the observation of Cassiopeia A (Cas A) taken some five years ago.

The duo spotted phosphorus in both subjects of the study, but the levels varied significantly. Crab Nebula holds much less of the element than Cas A.

As the two remnants were formed by the same type of supernova where the middle of the star implodes and rebounds rapidly, the group expected to see a similar amount of phosphorus, but this came as a surprise.

“The amounts seen so far don't match our computer models,” Greaves said in a statement. “I wondered what the implications were for life on other planets if unpredictable amounts of P [phosphorus] are spat out into space and later used in the construction of new planets."

Put simply, if some supernovae produce more phosphorus than others in the universe, like we see in this case, the chances of finding life could be restricted to just a few areas of our galaxy. However, the group believes understanding the cause of this discrepancy and observing other types of supernovae could help them get more insight into the distribution.

The pair stressed these are just preliminary results and more data will be needed to build on the findings.

“The two explosions seem to differ from each other, perhaps because Cas A results from the explosion of a rare super-massive star,” Cigan said in the same statement. “We've just asked for more telescope time to go back and check, in case we've missed some phosphorus-rich regions in the Crab Nebula."

Also, finding phosphorus content is just one piece of the puzzle. It also has to incorporate into biology to kickstart the process of life. On Earth, this is believed to have happened with meteorites which crashed on wet parts of the planet bringing phosphorus that was first used in cells to transfer energy and support complex life.

The findings of the observation will be presented at the European Week of Astronomy and Space Science in Liverpool.