- 3585 - PLANET NINE - is it out there? A new method for hunting minor planets uncovered more than a hundred small, distant worlds. The discovery of 139 new minor planets in the outer solar system, and especially the new method used to find them, might eventually help astronomers determine whether “Planet Nine” exists past Neptune.
--------------------- 3585 - PLANET NINE - is it out there?
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- We all learned that Pluto was “planet nine“. But, astronomy experts have reduced Pluto to a dwarf planet. So our Solar System has 8 planets now. And many dwarfs farther out. The decision occurred because astronomers kept discovering smaller planets orbiting outside the orbit of Neptune.
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- As of 2022, astronomers have discovered 139 new minor planets orbiting the Sun beyond Neptune by searching through data from the Dark Energy Survey. The new method for spotting small worlds is expected to reveal many thousands of distant objects in coming years, meaning these first hundred or so are likely just the tip of the iceberg.
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- Taken together, the newfound distant objects, as well as those to come, could resolve one of the most fascinating questions of modern astronomy: Is there a massive and mysterious world called “Planet Nine” lurking in the outskirts of our solar system?
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- Neptune orbits the Sun at a distance of about 30 astronomical units, 1 AU is the Earth-Sun distance. Beyond Neptune lies the “Kuiper Belt” , a comet-rich band of frozen, rocky objects (including Pluto) that holds dozens to hundreds of times more mass than the asteroid belt.
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- Both within the Kuiper Belt and past its outer edge at 50 AU orbit distant bodies called trans-Neptunian objects (TNOs). Currently, we know of nearly 3,000 TNOs in the solar system, but estimates put the total number closer to 100,000.
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- As more and more TNOs have been discovered over the years, some astronomers have noticed a small subset of these objects have peculiar orbits. They seem to bunch up in unexpected ways, as if an unseen object is herding these so-called “extreme TNOs” into specific orbits. Astronomers think these bizarrely orbiting TNOs point to the existence of a massive, distant world called “Planet Nine“.
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- Astronomers have discovered a number of far-flung objects that all have very similar perihelia, meaning they make their closest approaches to the Sun at about the same location in space. One leading theory that attempts to explain the clustering is that a massive and unseen world known as Planet Nine hiding in the outer solar system.
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- This Planet Nine is to be 5 to 15 times the mass of Earth and to orbit some 400 AU (or farther) from the Sun. The proposed Planet Nine would have enough of a gravitational pull that it could orchestrate the orbits of the extreme TNOs, causing them to cluster together as they make their closest approaches to the Sun.
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- The problem is that the evidence for Planet Nine is so far indirect and sparse. There could be something else that explains the clumped orbits, or perhaps researchers stumbled on a few objects that just happen to have similar orbits.
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- Discovering more TNOs, particularly beyond the Kuiper Belt, will allow astronomers to find more clues that could point to the location of the proposed Planet Nine, or, deny its existence altogether. Of the 139 newly discovered minor planets found in this study, seven are extreme TNOs.
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- The new TNOs were found by astronomers at the University of Pennsylvania using data from the “Dark Energy Survey“, (DES), which was not originally designed to look for distant minor planets.
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- “The Blanco Telescope” at the Cerro Tololo Inter-American Observatory in Chile houses the Dark Energy Camera, the primary tool of the Dark Energy Survey. Designed to reveal mysteries of dark energy in the universe, data from the survey could also help resolve the mystery of Planet Nine.
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- DES, an international effort to understand dark energy, began observing the southern skies in 2013, using an extremely sensitive camera mounted on the Blanco 4-meter telescope in the Chilean Andes.
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- Most astronomers trying to find TNOs have a dedicated way of looking at the sky where they take images a few hours apart and you can see the objects move very easily. The DES data didn’t work that way.
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- DES uses novel algorithms that could identify moving objects by connecting the dots between DES images, helping identify whether TNOs were present. The researchers then validated their movement-spotting algorithm against known TNOs and also confirmed that they could filter out fake objects.
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- Astronomers expect to find as many as 500 or more TNOs. Then, if the same method is applied to data from even more sensitive surveys on the horizon, such as by the new “Vera C. Rubin Observatory“, they expect discoveries of new TNOs to number in the thousands. And with those numbers, astronomers might finally get a definitive answer to whether or not our solar system is harboring a giant planet in its distant reaches.
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- It’s a fantastic example of how a survey designed for one area of astronomy, to study the expansion history of the universe, can also produce great science in a completely unrelated area.
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The hypothetical world called Planet Nine is expected to be a super-Earth or sub-Neptune planet with an orbit that potentially takes it dozens of times farther from the Sun than the dwarf planet Pluto. TNOs are difficult to detect, and so each one we find tells us that there is a much more massive underlying population of objects out there.
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- The more TNOs we discover, the more we can tell if there’s evidence for Planet Nine.
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May 21, 2022 PLANET NINE - is it out there? 3584
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