Astronomers have spotted molecular oxygen in another galaxy for the first ever time.
As well as being the gas that humans and other animals on Earth need to breathe, Oxygen is one of the most common elements in the universe – beaten only by hydrogen and helium – and so scientists long thought it would be easy to spot it elsewhere in the cosmos. But attempts to discover it turned up nothing, until the latest discovery.
Now researchers say they have found signs of oxygen in a galaxy called Markarian 231, 560 million lightyears away. That galaxy lies in the constellation Ursa Major and was already notable because it contains a bright quasar, where gas is swirled around a black hole and glows visibly through the universe.
As well as being the site of the first ever detection of breathable oxygen outside of our galaxy, Markarian 231 contains the most oxygen ever seen outside of our own solar system.
Astronomers from China's Shanghai Astronomical Observatory were able to spot signs of oxygen using radio telescopes on Earth.
Using that equipment, they saw radiation at a wavelength of 2.52 milimetres. That is the signal for O2 in its breathable form, leading researchers to that they had made the "first detection of extragalactic molecular oxygen", as they write in the paper published in the Astrophysical Journal.
Oxygen is so hard to see from Earth because many of the signals that would alert us to it are absorbed by Earth's atmosphere. The new discovery was possible in part because the light is redshifted as it travels through space, allowing it to be stretched out into a wavelength that could more easily get through the atmosphere.
While the gas is present in Markarian 231 in the form that humans breathe, actually travelling there and breathing it would not be possible. The swirl of gases present in the atmosphere does not have the same makeup as it does on Earth, and those other gases are required to allow humans to breathe in oxygen.
But the discovery offers an important way of tracking how O2 interacts with such extreme astrophysical areas, the scientists write, and further examination of the galaxy could allow us to learn about how oxygen is present through the rest of the cosmos.
And it also suggests that we may be able to find more oxygen, elsewhere in the universe. New equipment could be used to find oxygen elsewhere in the universe, the scientists involved write.