New research has a pair of scientists channeling Obi-Wan Kenobi from Star Wars: A New Hope in the detection of two moons orbiting planets outside the solar system. In short, they’re not sure that humanity’s first exomoon detections were accurate. In fact, the same findings also showed that echoeons in general can only manifest themselves if they are extremely large.
The research shows that while there is no reason to suggest that moons do not orbit worlds in other planetary systems, finding them is a difficult task. In the three decades since the first detection of an extrasolar planet, or “exoplanet,” the catalog of worlds around other stars has evolved, with more than 5,000 examples confirmed to date. But possible extrasolar moons, or “exomoons” orbiting these worlds, have eluded astronomers.
That was until 2018, when astronomers believed they had finally detected an echomone around the planet Kepler-1625 b, a Jupiter-like world located about 8,000 light-years from Earth. Then, in January 2022, astronomers believed they had detected a second exoplanet, this time orbiting exoplanet Kepler-1708 b, a gas giant 4.6 times the mass of Jupiter, located 5,400 light-years from Earth. Kepler-1708 b itself was only discovered in 2021.
But that still meant 5,000 known individuals. outer planets Or so, only two were found with satellites. But this wasn’t too much of a concern for astronomers because they thought the worlds were incredibly distant and that exoplanets should be much smaller than exoplanets. So they must be much harder to find, right? However, even these findings are now suspicious.
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“Echomoons are so far away that we cannot see them directly even with the most powerful modern telescopes,” said René Heller, team leader and scientist at the Max Planck Institute for Solar System Research (MPS). he said in a statement. “We would have liked to confirm the discovery of exomoons around Kepler-1625 b and Kepler-1708 b, but unfortunately our analyzes suggest otherwise.”
Pandora’s box reveals dire ‘planet only’ predictions
Exoplanets are often seen orbiting their host stars when they pass in front of the star, or “transit” the star, causing a small dip in the star’s light output. The method should also work on outer moons, but since these moons are much smaller than the worlds they orbit, any possible dip in the light they cause wouldn’t be as significant.
Additionally, an echo must be at a specific point in its orbit when scientists watch it pass; because the host planet also transits the star. Essentially, this moon needs to be in a very specific position relative to the planet so that it can block some of its own starlight. This is actually one of the reasons why evidence for the Kepler-1625 b ecotone appeared and then disappeared in Kepler Space Telescope data, only to reappear in later Hubble Space Telescope observations.
Heller and his colleagues reached the disappointing news about the outer moons of Kepler-1625 b and Kepler-1708 b by using the computer algorithm they developed called “Pandora”. Designed to accelerate the discovery of exoplanets, Pandora’s application to data collected by NASA’s Kepler Space Telescope aboard Kepler-1708 b revealed that scenarios with no exoplanet are just as likely to explain observations of this exoplanet and its star.
“The probability of a satellite orbiting Kepler-1708b is clearly lower than previously reported. The data do not indicate the presence of an exoplanet around Kepler-1708b,” said study co-author and astronomer Michael Hippke of the Sonneberg Observatory. expression.
Hippke and Heller suggest that for Kepler-1625 b, an effect called “stellar limb dimming,” which can cause changes in brightness across a star, affects the proposed outer lunar signal. They say the star’s limb dimming may better explain observations of the parent star than dimming caused by the presence of a potential alien moon.
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What’s more, the team’s research also offered bad news for exomoon hunters in general. When the duo used Pandora to predict the types of exomoons that could be detected by Kepler and other space telescopes from dips in light, they found that only particularly large moons (about twice the size of Ganymede, the largest moon in our solar system) were found. With current technology, their large orbits around their planets can be seen.
If other planetary systems were like the solar system, then a moon at such extremes would be very strange indeed. We know of about 290 moons in the solar system, and none of them fit this description; This means exomoon detection may be less likely than it currently is.
This research was published December 7 in the journal Nature Astronomy.