Brown, Mike (August 2008). Pluto, Eris, and the dwarf planets of the outer solar system (academic talk). Smithsonian. Event occurs at 50ᵐ. Archived from the original on 2021-11-14 . Retrieved 2 January 2019– via YouTube. The argument about dwarf planet sizes beyond Neptune is 50ᵐ into his talk. The WGBH link doesn't work; view on YouTube. Some of these include extremely close stars, such as one located only 20 light-years away in the constellation Norma. A study that looked at WISE data last year found a pair of brown dwarfs just 6.5 light-years from Earth, making it the closest star system discovered in almost 100 years. Patryk S., Lykawka; Tadashi, Mukai (2008). "An Outer Planet Beyond Pluto and the Origin of the Trans-Neptunian Belt Architecture". The Astronomical Journal. 135 (4): 1161–1200. arXiv: 0712.2198. Bibcode: 2008AJ....135.1161L. doi: 10.1088/0004-6256/135/4/1161. S2CID 118414447. a b Tom Standage (2000). The Neptune File: A Story of Astronomical Rivalry and the Pioneers of Planet Hunting. New York: Walker. p. 188. ISBN 978-0802713636. Astronomers soon discovered a moon orbiting Neptune, but it took more than a century to discover a second one. Our knowledge of distant Neptune greatly increased from the scientific observations made during Voyager 2’s flyby in 1989, including the discovery of five additional moons and confirmation of dark rings orbiting the planet." Neptune (Source: NASA on the commons)

At the turn of the 20th century, astronomers such as Percival Lowell continued to search for an even more-distant gas planet that could be responsible for disrupting the orbits of Uranus and Neptune. Clyde W. Tombaugh (1946). "The Search for the Ninth Planet, Pluto". Astronomical Society of the Pacific Leaflets. 5 (209): 73–80. Bibcode: 1946ASPL....5...73T. Matese, John J.; Whitmire, Daniel P. (2011). "Persistent evidence of a jovian mass solar companion in the Oort cloud". Icarus. 211 (2): 926–938. arXiv: 1004.4584. Bibcode: 2011Icar..211..926M. doi: 10.1016/j.icarus.2010.11.009. S2CID 44204219.Give each player all the pieces in one colour (1 player screen, 1 telescope miniature, 12 Theory Tokens) and 2 Target Tokens. If playing in Expert Mode, each player should also attach the ‘expert panel’ to the indicated slot in their player screen. Hasegawa, Kyoko (28 February 2008). "Japanese scientists eye mysterious 'Planet X' ". BibliotecaPleyades.net . Retrieved 18 July 2016.

S. C. Tegler & W. Romanishin (2001). "Almost Planet X". Nature. 411 (6836): 423–424. doi: 10.1038/35078164. PMID 11373654. S2CID 5135498. Additionally, speculation of a possible trans-Neptunian planet has revolved around the so-called " Kuiper cliff". The Kuiper belt terminates suddenly at a distance of 48AU (7.2billionkm; 4.5billionmi) from the Sun. Brunini and Melita have speculated that this sudden drop-off may be attributed to the presence of an object with a mass between those of Mars and Earth located beyond 48AU. [81]

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The need for the app isn’t as bad as you might imagine, and one of the biggest added benefits from its inclusion is the fact that you can play solo. Sure, you only play against one opponent, but the game you play is exactly the same game as you’ll play against human opponents, so it’s the perfect way to practice or to get a learning game in ahead of teaching it at your local game night. a b Kuiper, Gerard P. (August 1950). "The Diameter of Pluto". Publications of the Astronomical Society of the Pacific. 62 (366): 133–137. Bibcode: 1950PASP...62..133K. doi: 10.1086/126255.

a b Brown, Mike (11 April 2007). "Pluto and the outer solar system". Lowell Lectures in Astronomy. Boston, MA: Museum of Science, Boston / WGBH. Archived from the original on 2008-01-03 . Retrieved 2008-07-13.Pluto's size was finally determined conclusively in 1978, when American astronomer James W. Christy discovered its moon Charon. This enabled him, together with Robert Sutton Harrington of the U.S. Naval Observatory, to measure the mass of the Pluto–Charon system directly by observing the moon's orbital motion around Pluto. [41] They determined Pluto's mass to be 1.31×10 22kg; roughly one five-hundredth that of Earth or one-sixth that of the Moon, and far too small to account for the observed discrepancies in the orbits of the outer planets. Lowell's prediction had been a coincidence: If there was a PlanetX, it was not Pluto. [43] Further searches for Planet X [ edit ] On January 20, 2016, Brown and Konstantin Batygin published an article corroborating Trujillo and Sheppard's initial findings; proposing a super-Earth (dubbed Planet Nine) based on a statistical clustering of the arguments of perihelia (noted before) near zero and also ascending nodes near 113° of six distant trans-Neptunian objects. They estimated it to be ten times the mass of Earth (about 60% the mass of Neptune) with a semimajor axis of approximately 400–1500 AU. [8] [75] [76] Probability [ edit ] While the astronomical community widely agrees that PlanetX, as originally envisioned, does not exist, the concept of an as-yet-unobserved planet has been revived by a number of astronomers to explain other anomalies observed in the outer Solar System. [5] As of March 2014, observations with the WISE telescope have ruled out the possibility of a Saturn-sized object (95 Earth masses) out to 10,000 AU, and a Jupiter-sized (≈318 Earth masses) or larger object out to 26,000 AU. [6]

First, decide whether you want to play in Standard Mode (12 sectors) or Expert Mode (18 sectors). Place the sun disc in the centre of the board and overlay the earth board so that the yellow arrow is pointing into sector 1.The app also offers the useful option of providing players with different amounts of starting info, allowing for the option of a handicap system if some players are more experienced than others. But experience can come with another peril than just game balance: despite the fact each game will have a fresh setup to solve, doing so feels much the same every time. With limited ways to glean information, replayability is dependent on enjoying solving variants of that same puzzle. The Oort Cloud is also incredibly distant, with theinner edge between 2,000 and 5,000 AU from the Sun and the outer edge possibly up to 100,000 AU from the Sun (one AU is the distance separating Earth from the Sun).For comparison, Pluto’s elliptical orbit carries it between about 30 and 50 AU from the Sun. The possibility of a new planet is certainly an exciting one for me as a planetary scientist and for all of us," said Jim Green, director of NASA's Planetary Science Division. "This is not, however, the detection or discovery of a new planet. It's too early to say with certainty there's a so-called Planet X. What we're seeing is an early prediction based on modeling from limited observations. It's the start of a process that could lead to an exciting result." Is there a link? In December 2015, astronomers at the Atacama Large Millimeter Array (ALMA) detected a brief series of 350GHz pulses that they concluded must either be a series of independent sources, or a single, fast moving source. Deciding that the latter was the most likely, they calculated based on its speed that, were it bound to the Sun, the object, which they named "Gna" after a fast-moving messenger goddess in Norse mythology, [97] would be about 12–25 AU distant and have a dwarf planet-sized diameter of 220 to 880km. However, if it were a rogue planet not gravitationally bound to the Sun, and as far away as 4000 AU, it could be much larger. [98] The paper was never formally accepted, and has been withdrawn until the detection is confirmed. [98] Scientists' reactions to the notice were largely sceptical; Mike Brown commented that, "If it is true that ALMA accidentally discovered a massive outer Solar System object in its tiny, tiny, tiny, field of view, that would suggest that there are something like 200,000 Earth-sized planets in the outer Solar System ... Even better, I just realized that this many Earth-sized planets existing would destabilize the entire Solar System and we would all die." [97] Constraints on additional planets [ edit ]