Image Source: Space.com
The search for moons beyond our solar system has uncovered yet another possible lunar world, a moon larger than Earth orbiting a Jupiter-like planet. According to a report published in the journal Nature Astronomy, the planet and its moon, if it is a moon, orbit a Sun-like star over 5,000 light-years away. “Compared to any other moon in the solar system, the moon is pretty alien,” says David Kipping, an astronomer at Columbia University. “We’re not sure if it’s rocky, or if it’s gaseous.” It’s roughly the size of Neptune, which is gaseous, and Earth, which is rocky.”
This isn’t the first time astronomers have discovered what appears to be a moon in another planetary system, a phenomenon known as an exomoon. In fact, Kipping and his colleagues announced a few years ago that they’d discovered something resembling a moon orbiting another planet. That discovery has yet to be confirmed by additional telescope observations, and some astronomers are skeptical that it will withstand further scrutiny.
Because moons outnumber planets in our solar system, it stands to reason that planets orbiting other stars would have moons as well. Scientists want to find them, in part because a moon may have suitable conditions for life.
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“If you’ve seen Avatar or Star Wars, you’re probably familiar with the idea that moons could be habitable in and of themselves,” says Kipping. Real-life moons such as Jupiter’s Europa and Saturn’s Enceladus are thought to have features such as liquid water that could support life.
Scientists have discovered thousands of planets in recent years, but there has yet to be an unequivocal sighting of a moon orbiting any of them.
“Finding these exomoons is extremely difficult,” says Mary Anne Limbach, a Texas A&M University researcher who has also been looking for moons. “These detections are typically near the detection limit. As a result, it is frequently difficult to separate the noise from the exomoon signal.”
Existing telescopes are insufficiently powerful to allow astronomers to directly observe moons in other planetary systems. Instead, scientists can only speculate about the presence of a moon. If they notice a dimming pattern in a star, for example, it could mean that a moon and its planet are passing in front of the star and blocking some of its light.