While analyzing data from NASA’s Hubble and Kepler Space Telescopes, astronomers happen upon new exoplanets all the time. But the same can’t be said about exomoons, which are essentially moons residing in stellar systems beyond our own.
There’ve been a few instances previously where astronomers thought they’d discovered the first-known exomoon(s), but these have yet to be validated. Now, astronomers believe they’ve found yet another exomoon candidate. The findings have been published this week in the journal Science Advances.
Image Credit: Dan Durda
In the paper, we learn how there’s “compelling” evidence for a Neptune-sized exomoon residing some 8,000 light years away from Earth.
"This would be the first case of detecting a moon outside our solar system," explained study co-author David Kipping, a professor at Columbia University. "If confirmed by follow-up Hubble observations, the finding could provide vital clues about the development of planetary systems and may cause experts to revisit theories of how moons form around planets."
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Data from the Kepler Space Telescope provided the dead giveaway. The astronomers reportedly observed unusual light dimming anomalies coming from the system encompassing the massive exomoon.
Light dimming patterns are considered normal from exoplanet-containing systems because of how exoplanets pass in front of the host star during orbit; this blocked some of its starlight from reaching the Kepler Space Telescope. But the dimming anomalies discerned here were unusual – almost as if an exoplanet had its own natural satellite orbiting it.
"We saw little deviations and wobbles in the light curve that caught our attention," Kipping added.
To learn more, the team followed up with Hubble Space Telescope observations. To their amazement, Hubble detected similar patterns. The starlight dimming was timed consistently with how a moon would travel around its planet.
"An extraterrestrial civilization watching the Earth and Moon transit the Sun would note similar anomalies in the timing of Earth's transit," Kipping said.
The exomoon would need to be quite large to display the dimming anomalies that the astronomers observed. Estimates suggest that the exomoon could be as massive as the planet Neptune, while the host exoplanet would need to be several times more massive than Jupiter.
What’s more is that both the exoplanet and its exomoon seem to reside within the host star’s habitable zone, and while that might seem ideal for potential habitability, the astronomers say we shouldn’t hold our breath because both bodies likely sport gaseous compositions.
As of now, even the latest exomoon candidate detection is just that – a candidate. Additional research could validate or refute its existence, and while Hubble couldn’t provide all the answers in this study, NASA’s upcoming super-observatory, the James Webb Space Telescope, potentially could.
It should be captivating to learn whether this is genuinely the first-known exomoon or not, but only time will tell.