Solar System
The Sun and objects orbiting it
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| 2025 | The orbit estimation for Planet Nine was further updated to an even more precise semimajor axis measurement, continuing the ongoing refinement of its theoretical orbital parameters. |
| 2025 | Amir Siraj and colleagues published simulations proposing a revised mass estimate for Planet Nine at 4.4 ± 1.1 times that of Earth, different from previous calculations. |
| 2025 | Amir Siraj, Christopher F. Chyba, and Scott Tremaine conducted a study using 300 simulations in the Rebound program with an expanded sample of 51 ETNOs, proposing new orbital characteristics for Planet Nine: semi-major axis of 290 ± 30 AU, eccentricity of 0.29 ± 0.13, and an inclination of approximately 6°. |
| 2025 | Amir Siraj and colleagues published simulations proposing a revised mass estimate for Planet Nine at 4.4 ± 1.1 times that of Earth, different from previous calculations. |
| 2025 | The orbit estimation for Planet Nine was further updated to an even more precise semimajor axis measurement, continuing the ongoing refinement of its theoretical orbital parameters. |
| 2024 | Brown and Batygin completed a simulation demonstrating how the hypothetical Planet Nine would modify the orbits of extreme trans-Neptunian objects (ETNOs), increasing their eccentricities over time and potentially causing them to cross Neptune's orbit. |
| 2024 | Brown and Batygin completed a simulation demonstrating how the hypothetical Planet Nine would modify the orbits of extreme trans-Neptunian objects (ETNOs), increasing their eccentricities over time and potentially causing them to cross Neptune's orbit. |
| 2023 | Researchers demonstrated that modified Newtonian dynamics (MOND) could provide an alternative explanation for the observed clustering of Kuiper Belt Object (KBO) orbits, potentially challenging the Planet Nine hypothesis by predicting orbital alignments with the Galactic Center using secular approximations. |
| 2023 | Researchers demonstrated that modified Newtonian dynamics (MOND) could provide an alternative explanation for the observed clustering of Kuiper Belt Object (KBO) orbits, potentially challenging the Planet Nine hypothesis by predicting orbital alignments with the Galactic Center using secular approximations. |
| April 2023 | The Catalina Outer Solar System Survey project concludes after nearly three years of citizen science research into potential astronomical discoveries. |
| April 2023 | The Catalina Outer Solar System Survey project concludes after nearly three years of citizen science research into potential astronomical discoveries. |
| 2022 | A comparison between IRAS and AKARI infrared data was conducted, yielding no detection of Planet Nine, with researchers noting difficulties in detecting thermal emissions near the galactic plane. |
| 2022 | A comparison between IRAS and AKARI infrared data was conducted, yielding no detection of Planet Nine, with researchers noting difficulties in detecting thermal emissions near the galactic plane. |
| May 2022 | A hypothesis was proposed suggesting that the interstellar meteor CNEOS 2014-01-08 might have entered Earth-crossing orbit after an encounter with Planet Nine, potentially indicating the theoretical planet's location in the constellation of Aries at right ascension 53° and declination 9.2°. |
| May 2022 | A hypothesis was proposed suggesting that the interstellar meteor CNEOS 2014-01-08 might have entered Earth-crossing orbit after an encounter with Planet Nine, potentially indicating the theoretical planet's location in the constellation of Aries at right ascension 53° and declination 9.2°. |
| 2021 | Batygin and Brown searched the first three years of data from the Zwicky Transient Facility (ZTF) without identifying Planet Nine. This search ruled out 56% of the parameter space for possible Planet Nine positions. |
| 2021 | Orbit estimation for the hypothetical Planet Nine was refined, resulting in a somewhat smaller semimajor axis of 380 AU, reducing the previous estimated orbit range. |
| 2021 | Batygin and Brown searched the first three years of data from the Zwicky Transient Facility (ZTF) without identifying Planet Nine. This search ruled out 56% of the parameter space for possible Planet Nine positions. |
| August 2021 | Batygin and Brown reanalyzed data related to Extreme Trans-Neptunian Object (ETNO) observations, accounting for observational biases and finding orbital clustering significant at a 99.6% confidence level. They predicted Planet Nine's characteristics, including a semi-major axis of 380 AU, perihelion of 300 AU, orbital inclination of 16°, and a mass of 6.2 Earth masses. |
| August 2021 | Batygin and Brown reanalyzed data related to Extreme Trans-Neptunian Object (ETNO) observations, accounting for observational biases and finding orbital clustering significant at a 99.6% confidence level. They predicted Planet Nine's characteristics, including a semi-major axis of 380 AU, perihelion of 300 AU, orbital inclination of 16°, and a mass of 6.2 Earth masses. |
| 2020 | The Outer Solar System Origins Survey (OSSOS) and Dark Energy Survey (DES) published results challenging the Planet Nine hypothesis, with both surveys concluding there was no evidence for orbital clustering after adjusting for observational bias. |
| 2020 | The Outer Solar System Origins Survey (OSSOS) and Dark Energy Survey (DES) published results challenging the Planet Nine hypothesis, with both surveys concluding there was no evidence for orbital clustering after adjusting for observational bias. |
| December 2020 | Researchers determined that HD 106906 b, an exoplanet with an eccentric orbit outside its binary host stars' debris disk, could potentially serve as a proxy for understanding Planet Nine's orbital evolution. |
| December 2020 | Researchers determined that HD 106906 b, an exoplanet with an eccentric orbit outside its binary host stars' debris disk, could potentially serve as a proxy for understanding Planet Nine's orbital evolution. |
| August 2020 | Zooniverse launches the 'Catalina Outer Solar System Survey' project, a citizen science initiative using archived Catalina Sky Survey data to search for Trans-Neptunian Objects (TNOs). |
| August 2020 | Zooniverse launches the 'Catalina Outer Solar System Survey' project, a citizen science initiative using archived Catalina Sky Survey data to search for Trans-Neptunian Objects (TNOs). |
| April 2020 | Scott Lawrence and Zeeve Rogoszinski proposed using multiple spacecraft as an alternative method to detect the hypothetical Planet Nine, suggesting spacecraft could have advantages over land-based telescopes. |
| April 2020 | Scott Lawrence and Zeeve Rogoszinski proposed using multiple spacecraft as an alternative method to detect the hypothetical Planet Nine, suggesting spacecraft could have advantages over land-based telescopes. |
| 2019 | Scholtz and Unwin suggested a detection method for the hypothetical primordial black hole, proposing that interactions with surrounding dark matter could produce detectable gamma rays using the FERMILAT instrument. |
| 2019 | A study estimated that Planet Nine may be smaller and closer than originally thought, potentially making it brighter and easier to detect with an apparent magnitude of 21–22. |
| 2019 | Mike Brown gave a lecture referencing the 'Planet Nine from Outer Space' wordplay, continuing the humorous connection to the Ed Wood film. |
| 2019 | Jakub Scholtz and James Unwin proposed a hypothesis that a primordial black hole, rather than a planet, could be responsible for the clustering of Extended Trans-Neptunian Object (ETNO) orbits, based on analysis of OGLE gravitational lensing data. |
| 2019 | Mike Brown gave a lecture referencing the 'Planet Nine from Outer Space' wordplay, continuing the humorous connection to the Ed Wood film. |
| 2019 | Jakub Scholtz and James Unwin proposed a hypothesis that a primordial black hole, rather than a planet, could be responsible for the clustering of Extended Trans-Neptunian Object (ETNO) orbits, based on analysis of OGLE gravitational lensing data. |
| 2019 | Scholtz and Unwin suggested a detection method for the hypothetical primordial black hole, proposing that interactions with surrounding dark matter could produce detectable gamma rays using the FERMILAT instrument. |
| February 2019 | Batygin and Brown updated their hypothesis about Planet Nine, analyzing an increased number of Extreme Trans-Neptunian Objects (ETNOs) to fourteen, refining the potential orbital parameters of the hypothetical planet. |
| February 2019 | Batygin and Brown updated their hypothesis about Planet Nine, analyzing an increased number of Extreme Trans-Neptunian Objects (ETNOs) to fourteen, refining the potential orbital parameters of the hypothetical planet. |
| 2018 | Astrophysicist Ethan Siegel published an article suggesting the observed clustering of extreme trans-Neptunian objects (ETNOs) could be due to observational bias. |
| 2018 | Planetary scientist Alan Stern and 34 other scientists objected to the name 'Planet Nine', proposing alternative names like 'Planet X' or 'Planet Next', arguing it diminishes Clyde Tombaugh's legacy. |
| 2018 | Planetary scientist Alan Stern and 34 other scientists objected to the name 'Planet Nine', proposing alternative names like 'Planet X' or 'Planet Next', arguing it diminishes Clyde Tombaugh's legacy. |
| 2018 | Astrophysicist Ethan Siegel published an article suggesting the observed clustering of extreme trans-Neptunian objects (ETNOs) could be due to observational bias. |
| December 2018 | Brown and Batygin conducted observational searches for Planet Nine using the Subaru Telescope, spending four half-nights and three full nights scanning the sky near Orion. |
| December 2018 | Brown and Batygin conducted observational searches for Planet Nine using the Subaru Telescope, spending four half-nights and three full nights scanning the sky near Orion. |
| 2017 | Carlos and Raúl de la Fuente Marcos published research noting a potential bimodal distribution of ascending node distances among Trans-Neptunian Objects, suggesting the influence of a hypothetical planet with a semi-major axis between 300-400 AU. |
| 2017 | Physicist Lorenzo Iorio informally suggested naming the hypothetical planet 'Telisto', derived from the ancient Greek word meaning 'farthest' or 'most remote'. |
| 2017 | Physicist Lorenzo Iorio informally suggested naming the hypothetical planet 'Telisto', derived from the ancient Greek word meaning 'farthest' or 'most remote'. |
| 2017 | Carlos and Raúl de la Fuente Marcos published research noting a potential bimodal distribution of ascending node distances among Trans-Neptunian Objects, suggesting the influence of a hypothetical planet with a semi-major axis between 300-400 AU. |
| 2016 | Scientific American published an article titled 'Planet Nine from Outer Space' about the hypothesized planet in the outer region of the Solar System, making a playful reference to Ed Wood's 1959 science fiction film. |
| 2016 | Holman and Payne conducted an analysis of Pluto's orbit, finding perturbations that differed significantly from the previously proposed orbit of Planet Nine by Batygin and Brown. They proposed three potential explanations for these orbital discrepancies, including the possibility of an unmodeled mass in the Solar System. |
| 2016 | Batygin and Brown investigated the orbits of Trans-Neptunian Objects (TNOs) with large semi-major axes, finding a statistically improbable clustering of orbital characteristics that suggested the potential existence of an undiscovered planet. |
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