Astronomers were surprised when they first managed to detect oxygen outside of our Milky Way galaxy. Molecular oxygen has been identified more than half a billion light-years from Earth. This is only the third such detection outside the solar system and the first outside the Milky Way.
Oxygen is the third most abundant element in the universe, second only to hydrogen and helium. The discovery was made through detailed observations in the direction of the galaxy Markarian 231 using the 30-meter IRAM and NOEMA telescope.
Oxygen chemistry and its content in interstellar clouds are critical to understanding the role of molecular gas in galaxies. However, despite repeated searches, overall there is a surprising lack of oxygen molecules. Here is what the team of astronomers who made the discovery, led by Dr. Junzhi Wang of the Chinese Academy of Sciences, noted about this:
“This means that there is still no comprehensive picture of oxygen chemistry in various interstellar media.”
Prior to this, another place where molecular oxygen was discovered was identified – the Orion Nebula. It has been suggested that oxygen is bonded to hydrogen in the form of water ice clinging to cosmic dust particles.
But the Orion Nebula is a star-forming region, and perhaps the intense radiation from very hot young stars sublimates water ice and splits molecules, releasing oxygen.
At the same time, the galaxy Markarian 231, located at a distance of about 561 million light years, is completely different. The galaxy is powered by a quasar emitting light from a galactic core with an active supermassive black hole at its center.
Astronomers believe Markarian 231 may have two active supermassive black holes at the center, orbiting violently around each other. The active galactic nucleus leads to an outflow of molecules, creating continuous explosions that can release oxygen from water in molecular clouds.
The molecular outflow to Markarian 231 is especially high, so Dr. Wang and his team turned their 'gaze' there for the purpose and search for oxygen and were not mistaken. Using the 30-meter IRAM radio telescope in Spain, the researchers observed the galaxy for four days at several wavelengths. The data obtained did show the spectral signature of oxygen, which caused a kind of shock.
Thanks to detailed observations in the direction of Markarian 231 using the 30-meter IRAM and NOEMA telescope, scientists have detected for the first time the emission of molecular oxygen in the outer galaxy. The detected O2 emission was detected in regions located about 32 615 light years from the center of the galaxy Markarian 231. According to the researchers, this may be caused by the interaction between the active molecular flow, controlled by the galactic nucleus, and the molecular clouds of its outer disk.
