For the first time, a group of chemists affiliated with the University of Arizona’s Department of Astronomy and Steward Observatory detected phosphorous on the outskirts of the Milky Way galaxy. Lilia Koelemay, Karlie Gold, and Lucy Ziurys investigated the gas cloud WB89-621 in their study, which was published in the journal Nature.
Prior study has proven that phosphorous exists near the sun and in other inner portions of the Milky Way galaxy, but it has not been found in the galaxy’s outer parts until now. Previous findings were not surprising, given previous research has demonstrated that phosphorous is formed when silicon atoms in stars (such as the sun) interact with neutrons. The detected phosphorous is thought to be the result of star nucleosynthesis.
It also appears to explain why phosphorous has not been discovered further away from the sun—there is no realistic mechanism for it to get there. The researchers were researching the chemical makeup of gas cloud WB89-621, which is located near the Milky Way’s outer margins when they discovered something unexpected.
The researchers were analyzing millimeter spectra of PO and PN when they noticed rotating lines indicating the presence of phosphorous in the cloud, which was 22.6 kpc from the center of the Milky Way galaxy. They also remark that supernovae do not exist in the Milky Way’s outer regions, implying that the phosphorous they witnessed came from somewhere else.
The researchers point out that two possible sources are untrustworthy. Galactic fountains, for example, which transfer material from supernovae via circumgalactic and/or halo effects, could not explain their discovery because clouds formed by such fountains are not seen in the Milky Way at such distances.
Another possibility is that the contribution came from an extragalactic source, such as the Magellanic Cloud. However, they remark that this appears improbable because such sources rarely have enough metals to produce the levels of phosphorous found.
To ascertain the source of the phosphorus discovered, the team decided that other alternative sources must be studied.
