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The recent possible discovery of Planet Nine by Batygin & Brown (2016) has caused quite a stir, in the astronomy community, Astronomy Stack Exchange, and the rest of the world. This is, of course, in part because any mention of such a discovery will cause a stir, but it is also in part because of the claimed probability if the movements of the Trans-...

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If such a planet exists, WISE should observe it. WISE is an infrared satellite that imaged the entire sky. In particular: it was able to detect anything with a temperature above 70-100 K, whereas the coolest known exoplanets are in the 100 K range (see histogram below, taken from the Exoplanets Catalogue); it was able to detect objects larger than 1km up to ...

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This Wikipedia page does a decent job of describing the orbit-clearing criterion, based on the original paper by Stern & Levison (2002), which can be found here (PDF). In order to have cleared its orbit over a period of billions of years, an object needs a "Stern-Levison parameter" $\Lambda$ which is $> 1$; Pluto has $\Lambda \approx 3$-$4 \times 10^{... 5 For this, I'll point you to the IAU's List of Transneptunian Objects. That page provides a table of every known TNO along with all sorts of data about each TNO, including date of discovery. You could very easily determine how the rate of discovery has changed over time. As a related resource, there is the Wikipedia page List of unnumbered trans-Neptunian ... 5 Yes there is a difference, Kuiper Belt Objects (KBOs) are a subset of Trans Neptunian Objects (TNOs). Other subsets are Oort-cloud objects (OCOs) and scattered disk objects (SDOs). These are not KBOs but they are TNOs. See for instance this wikipedia page. 3 The main problem with determining an object's orbit is we only know the position with certainty in two dimensions. The distance to the object is largely unknown. This accounts for the large uncertainty in the period of newly discovered TNOs. Many possible orbits could fit the early observations, and therefore the uncertainty is large. As time goes on, ... 2 This is the result of a new way to investigate the images taken by the PanSTARRS survey, see Weryk et al. 2016. A second batch of new discoveries was issued on July 26. This has been planned for several years, and now there's enough data to get useful results. Note that Gareth Williams from the MPC has currently some technical problems with the most recent ... 2 You've asked a big question, too big perhaps for a Q&A forum such as this. Your question is the sole subject of graduate level aerospace engineering classes, e.g., University of Colorado ASEN 5070, Introduction to Statistical Orbit Determination, and is the subject of multiple graduate level texts, e.g., Statistical Orbit Determination by Bob Schutz, ... 1 The IAU does not give a definition of "asteroid" (in contrast to its defintion of "planet") The definition of "asteroid" is therefore determined by actual use, rather than a specific authoritative source. The IAU in its guidelines on "naming" doesn't use the term "asteroid" (except qualified as "near earth asteroid". The term is somewhat ambiguous. Instead ... 1 As we know, Pluto is within the Kuiper belt, and it only makes up about$0.077\%$times the mass of all of the object within its orbit. Now, in comparison, Earth has objects in its orbit, but it is$1.7\$ million times the mass of all of the objects. It's been debated in the past (by supporters of Pluto being a planet) that if Earth were in Pluto's place, ...

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