NASA Goddard Space Flight Center recently released a stunning image by the Hubble Space Telescope of a megamaser—a galaxy that is basically one giant laser in space.
Iras 16399-0937, as the galaxy is called, does not blast visible light. It’s a little longer on the electromagnetic spectrum, in the microwave range. And there’s a lot going on out there. Unlike our own Milky Way galaxy, which has one core at its center, Iras has two, and they are merging slowly. The southern core, as one of the pair is called, is a star factory. The northern core, meanwhile, hosts a black hole that’s 100,000,000 times the mass of our Sun. The interaction of the two, and consequent galactic turmoil, gives the galaxy its beautiful shape.
The image was captured using two instruments on Hubble: the Near Infrared Camera and Multi-Object Spectrometer (which was superseded by the more capable Wide Field Camera 3 in 2009) and the Advanced Camera for Surveys, which was installed on Hubble in 2002 and is still in use.
SET MASERS ON STUN
Maser is actually an acronym: Microwave Amplification by Stimulated Emission of Radiation. So was laser, at least initially: Light Amplification by Stimulated Emission of Radiation. That's the difference between the two: microwave versus light. They're both coherent energy beams, but a maser emits microwave radiation, while a laser emits visible light. Einstein proposed the basic principle in 1917. Masers are used in everything from atomic clocks to NASA’s Deep Space Network. In the case of the latter, giant dishes receive weak signals from spacecraft as far from Earth as the interstellar medium. Cryogenically cooled ruby masers cleanly amplify the signals and allow data to be extracted.
You might not have heard of masers—only lasers—but there was a time when the opposite was true for many. “Phasers” on Star Trek are a shortened form of “photon maser.” Lasers had only been invented a few years before the debut of the television series. To the extent they were known, they certainly weren’t thought to be as powerful as the mighty maser, which was first built in 1953. (Gene Roddenberry worried during filming of the second pilot that people would say, "Oh, come on, lasers can't do that.") Even shortly after the laser was invented, theoretical work on masers led to a Nobel Prize in Physics in 1964.
Sometimes stimulated emissions of radiation occur naturally. Vaporized molecules in comets can mase, as can protostars in stellar nurseries. Sometimes masers go big time. A megamaser like Iras is 100 million times brighter than the dinky masers of the Milky Way. With that kind of power, the host galaxy itself is basically a cosmic maser beaming microwave emissions across the universe. There are also gigamasers, which are a billion times brighter than our masers, but that’s just showing off.
Extragalactic masers are useful to astronomers for, among other things, the independent calculation of the galaxy’s distance. Iras, for example, is 370 million light-years from Earth. For comparison, the closest star to our own—Proxima Centauri, of the Alpha Centauri star system—is 4.4 light-years away. Because of how nicely light-years scale, if the Earth were one inch from the Sun, Iras would be 370 million miles away. While we won’t be visiting anytime soon, we can still enjoy its natural, tempestuous beauty.