Should you search for on a transparent evening, the brightest and largest object within the sky will most likely be the moon. And until you’ve gotten a good telescope, it’s the solely pure satellite tv for pc you’ll be able to see with your personal eyes. Consequently, most individuals have a warped notion of what a moon is and the way widespread these pure satellites actually are.In actuality, there are tons of, if not 1000’s, of pure satellites, in our cosmic neighborhood, starting from irregular town-size house rocks to huge rounded our bodies which can be doubtlessly sufficiently big to be thought-about planets in their very own proper.So precisely what number of photo voltaic system moons have we discovered? The reply, it seems, is determined by your definition of a moon. The Worldwide Astronomical Union (IAU) formally acknowledges 288 planetary moons orbiting the photo voltaic system’s eight worlds, based on NASA. However there are additionally an extra 473 “small-body satellites” — the moons of asteroids and dwarf planets — listed by NASA’s Jet Propulsion Laboratory. If we rely each varieties, as most astronomers would, this brings the overall variety of pure photo voltaic system satellites to 761 (as of June 2024). However that is possible simply “the tip of the iceberg,” Edward Ashton, an astronomer on the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, advised Stay Science in an electronic mail. Astronomers have discovered dozens of recent planetary moons and small-body satellites in the previous couple of years alone, and technological developments will possible speed up the speed at which they will spot extra within the coming years, he added.What’s a moon? “The best definition [of a moon] could be an object that’s in an orbit round a bigger, non-stellar object,” Ashton advised Stay Science. “However that isn’t fairly the entire reply.” For instance, there are presently 1000’s of human-made satellites in orbit round Earth that fulfill the definition above however should not thought-about moons as a result of they don’t seem to be pure. These spacecraft even have restricted life spans earlier than falling again to Earth and burning up in our environment.Get the world’s most fascinating discoveries delivered straight to your inbox.Some pure satellites, comparable to quasi-moons and minimoons, are additionally non permanent and don’t actually orbit planets. Associated: Will Earth ever lose its moon?A quasi-moon quickly orbiting the solar alongside Earth might look as whether it is in orbit round our planet. However it isn’t. (Picture credit score: Zoonar GmbH / Alamy Inventory Picture)There may be additionally a query of measurement, Brett Gladman, an astronomer on the College of British Columbia in Canada, advised Stay Science in an electronic mail. For instance, ring particles — the tiny fragments of rock that make up the rings of planets like Saturn and Uranus — individually orbit their host planet however should not thought-about moons, Gladman stated. Objects smaller than just a few hundred toes, sometimes called “ring moons” or “moonlets,” even have “fuzzy definitions” and should not thought-about true moons, Gladman added. Even amongst acknowledged moons, there are nonetheless factors of competition. For instance, planetary moons may be cut up into two teams: common moons, that are usually bigger and have small, round orbits near the equator of their host planet; and irregular moons, which may be a lot smaller and have bigger, extra elliptical orbits round their host planets, Ashton stated. Among the many common moons, round 20 are additionally thought-about main moons — that means they’re giant sufficient to have a rounded form brought on by their gravity, based on The Planetary Society.Planetary moons Beginning closest to the solar, our dwelling star’s nearest neighbors, Mercury and Venus, haven’t any true moons due to their proximity to the large ball of fuel, which might have ripped away any potential moons from the planets way back. Venus does have one recognized quasi-moon, Zoozve, however this doesn’t rely as a result of it really orbits the solar, not Venus.Transferring on, we come to Earth. Our dwelling planet has only one main moon. Nevertheless, it additionally has no less than seven quasi-moons and infrequently positive aspects extra minimoons for round a 12 months at a time. These lunar imposters don’t rely, both. Nevertheless, some scientists suppose we might use these house rocks as non permanent bases to assist us turn into an interplanetary species.Subsequent up is Mars, which has two true moons: Phobos and Deimos. Each are just some miles extensive and orbit very near the Purple Planet. Phobos is slowly falling towards Mars and is predicted to crash into the world’s floor sometime — if it isn’t ripped aside first.Mars’ moons, Phobos and Deimos, are every just some miles extensive and orbit the Purple Planet a lot nearer than the moon orbits Earth. (Picture credit score: Shutterstock)As we transfer on to the large planets, issues begin to get extra attention-grabbing. The primary fuel big, Jupiter, has a whopping 95 moons, together with 4 main moons — Callisto, Europa, Io and Ganymede, the most important moon within the photo voltaic system. However Saturn has much more: There are no less than 146 Saturnian moons, together with six main moons, comparable to Titan, Mimas and Enceladus. The ice giants Uranus and Neptune have 28 and 16 moons, respectively, and 7 main moons between them. Associated: The place does the photo voltaic system finish?However these numbers have modified considerably up to now few years alone. Because the begin of 2023, astronomers, together with Ashton and Gladman, have discovered no less than 62 new irregular moons round Saturn and 12 new Jovian moons, in addition to a pair of Neptunian moons and a single moon round Uranus. The geysers of Saturn’s main moon Enceladus point out it might have the circumstances wanted to assist extraterrestrial life. (Picture credit score: NASA)Developments in know-how can clarify the sudden improve in moon discoveries. Extra highly effective telescopes can spot smaller moons — notably irregular moons — which can be ample round big planets, Ashton stated.Consequently, the variety of moons is prone to proceed to rise sharply over the subsequent few years. For instance, Ashton revealed that he has already found some extra planetary moons however continues to be ready for follow-up observations to substantiate their existence earlier than submitting them to the IAU.The variety of planetary moons may additionally improve if we discover extra planets within the photo voltaic system. One such world is the elusive Planet 9 — a hypothetical big planet that will lurk within the far reaches of the photo voltaic system. If this planet does exist, researchers have already hypothesized that it could possibly be surrounded by a number of moons. Researchers have additionally speculated that extra distant worlds captured from interstellar house by the solar’s gravitational pull, referred to as rogue planets, might even have moons. Small-body satellitesNASA’s rely of 473 small-body satellites is much more unsure than the variety of planetary moons as a result of we’re discovering extra asteroids on a regular basis. Some asteroids may also have a number of satellites which can be onerous to differentiate from each other, Ashton stated.The IAU additionally estimates that there could possibly be “greater than 100″ further dwarf planets ready to be discovered within the outer photo voltaic system, all of which might have moons.Pluto’s largest moon Charon might be sufficiently big to be thought-about a significant moon if it orbited a real planet. (Picture credit score: NASA/JHUAPL/SwRI)”Similar to the large planet satellites, we’re but to find the overwhelming majority of them,” Ashton stated. In complete, there’ll most likely be “round as many small-body satellites as planetary moons,” he added.Nevertheless, different astronomers, like Gladman, are much less positive about what number of small-body satellites there could also be. “A lot of the ‘father or mother’ inhabitants [of host objects] continues to be not recognized that it’s tough to handle this query,” he stated.What number of moons might there be in complete? There are greater than 700 recognized pure satellites within the photo voltaic system. Nevertheless, as we have now seen, this quantity is prone to develop considerably sooner or later.Previous research have proven that there could possibly be tons of, if not 1000’s, of tiny planetary moons that could possibly be found with extra highly effective telescopes, Gladman stated. And as we have now already seen, there may be nice uncertainty about what number of small-body satellites are actually on the market.However this uncertainty would not cease researchers from having the ability to enterprise a guess. “I believe that there are most likely about 10,000 moons within the photo voltaic system,” Ashton stated. However there isn’t any telling how lengthy it might take us to seek out all of them.