Drinkability: Low.

What is a maser? Well, it’s just like a laser, but with an “m”. Really, though. M.A.S.E.R. stands for Microwave Amplification by Stimulated Emission of Radiation. It functions exactly the same as a laser does, but just shines at a longer wavelength than the visible light of a laser.

The ingredients for any laser or maser are relatively simple: a heat source, a gas, a long path, and a cooling mechanism. As unbelievable as it may seem, there are naturally occurring masers in space.

These water masers appear around stars, in interstellar gas, and in the active nuclei of galaxies. The latter gives birth to an especially interesting form of maser. These so-called megamasers are powered by the active supermassive black hole (a million to a billion times the mass of our sun) in the center of a galaxy. The name “mega” comes from the fact that these masers are 1 million times brighter than any other type of maser and more than ten times brighter than our own sun.


An image of Messier 106 (a.k.a. NGC 4258) composed of X-ray and radio observations. The zoom shows the warping of the accretion disk as revealed by the water maser. The reason we can see a water maser in this galaxy is that it, and therefore the accretion disk, are nearly edge-on. This allows the maser a long enough gain path to shine.

Photo by: James M. Moran

In Messier 106, a relatively nearby galaxy 24 million light years from Earth, a maser was detected in the disk of material orbiting around and feeding the active supermassive black hole. The accretion disk – as the disk of material is known – is the perfect candidate for a water maser. Think back to that recipe for a maser: heat, gas, long path, and a cooling mechanism. In the accretion disk, the megamaser has the black hole as a heat source, water gas in the disk, a long path when the disk is viewed edge-on, and the flat geometry of the disk, which is optimal for cooling.

Discovered in 1999, the water megamaser in the accretion disk of Messier 106 facilitated what was then the most accurate measurement ever of a black hole’s mass. It also helped astronomers make extremely accurate measurements of the distance to the galaxy, which, in turn, was used to help measure the expansion rate of the universe. If those nuggets weren’t enough to consider this water maser a treasure trove of information, the maser also provided such detailed resolution of motion in the accretion disk, that observers were able to determine that the disk had a warp in it. Thanks to the water maser, astronomers made the huge leap from only suspecting that accretion disks were present around active supermassive black holes, to being able to tell a disk’s exact shape.

All things considered, this galaxy is actually relatively close to Earth. If we continue our journey outward, to a galaxy more than 100 times farther away, we can get a glimpse of the most distant water discovered in our universe.

Distance to next destination:  70 sextillion miles (12 billion light years)

To stay hydrated, drink: 2 sextillion gallons (or, the weight of Mars in water)

About The Author

Madelyn Broome

Madelyn was the 2018 Editor-in-Chief of Innovation, and a former writer and editor for the Space/Physics section. Her piece "Where's the Water?" won the 2019 Gregory T. Pope Prize for Science Writing. She is passionate about science communication and about making science engaging and accessible for people of all ages - though she especially enjoys working to ignite excitement for the sciences in young girls and other underrepresented communities in STEM. When she's not trying to share her enthusiasm for the sciences, she can usually be found exploring, practicing mixed martial arts, archery, lifting, playing soccer, or just generally trying to make up for the dessert she just ate.