In the quest to find moons in faraway solar systems, the explorers of astrophysics are stuck in a rut.
Or so believes University of Texas at Arlington physics professor Zdzislaw Musielak.
Most of their methods are based on observing variations in light from a star, which has worked well for detecting foreign planets — more than 1,800 since the first one was found, most likely in 1992.
But, to date, zero moons have been found orbiting those planets.
Musielak has a new approach. He and his two Ph.D. graduate student researchers Joaquin Noyola and Suman Satyal have been studying how to use radio wave emissions, instead of starlight, to detect moons. They believe their way is more accurate
“My idea came several years ago,” Musielak said. “I felt like, ‘Hmmm, why have we never tested it this way.’ ”
He and his student collaborators published their findings in the Aug. 10 issue of The Astrophysical Journal, in which they detailed their work analyzing radio waves created by the interaction between Jupiter’s magnetic field and one of its largest moons, Io.
Under the laws of physics, they figured, what happens between Jupiter and Io could could happen anywhere.
“The reason it would work is because it’s working in the solar system,” Musielak said. “It would be a natural way to extend this beyond the solar system.”
Musielak emphasizes that they have not found a moon — often called exomoons, which orbit exoplanets — or even searched for one yet. But they’ve created a how-to guide for all observers to use when moon hunting. Musielak gives Noyola, who took Musielak’s idea and instigated the research, most of the credit for developing the criteria for those directions.
The team plans to attempt its own search and is preparing a proposal to use an observatory’s radio telescope.
“We are more on the theoretical side,” Musielak said. “Right now, as of today, this is just an idea.”
Discoveries of moons could depend on more sensitive radio telescopes of the future. Noyola, the lead author of the paper, said there are several such scopes in various stages of construction around the world.
“There are at least four telescopes that are partially completed and would have a good chance of finding an exomoon,” he said.
Most researchers analyze starlight data for evidence that exoplanets exist. In one method, they try to determine if barely perceptible decreases in a star’s brightness can be attributed to a planet passing between its star and Earth viewers.
In the other, observers evaluate the data to find evidence that something in orbit is pulling at the star.
So far, they’ve only succeeded in ferreting out planets, but supporters believe elements of those techniques could be valuable for detecting moons as well, especially as technology advances.
Moon hunting matters, astrophysicists say, because most of the discovered exoplanets are gas giants, like Jupiter, with inhospitable, even violent atmospheres not likely to sustain life. But those planets occupying habitable zones, sometimes called Goldilocks zones — they’re just the right distances from their suns or have just enough volcanic activity to provide warmth — could have hospitable moons with liquid water.
“If they’re rocky and big enough like Earth, it can hold the atmosphere,” Satyal said. “And with atmosphere there is more of a chance for life.”
Maybe not humanesque. “In general, life can be in any form, like microorganisms,” he said.
The mathematical odds seem to clearly favor the life-exists camp. In addition to the 1,800 confirmed planets, NASA’s Kepler space telescope has gathered data on thousands of other possible planets. Our own solar system has more than 170 moons, 129 of which are orbiting Jupiter and Saturn. Then factor in the hundreds of billions of stars and potential solar systems in the Milky Way galaxy alone.
Musielak said there must be countless moons of the size and composition of Earth or Mars.
“Maybe we find one of those moons located in the habitable zone, and it may be big enough to have an atmosphere,” he said. “There could be a civilization on a moon like that.”