It’s been a tumultuous few years for Pluto. The dwarf planet, first discovered in 1930 by astronomer Clyde Tombaugh, was stripped of its more esteemed planet status in 2006 by the International Astronomical Union (IAU) because its orbit overlapped that of Neptune. A new set of IAU criteria mandated that a planet must orbit the sun, be spherical as a result of gravity, and "clear" the "neighborhood" around its orbit, asserting itself as the dominant presence. Pluto met the first and second edicts but not the third, relegating it to the lesser dwarf planet designation. That declaration led to an ongoing debate over whether Pluto really earned its demotion. The newest and potentially most compelling argument comes courtesy of a paper from researchers at the University of Central Florida's Space Institute and published in the planetary science journal Icarus. In it, first author Philip Metzger asserts that no one since 1802 has used the cleared-space argument to define a planet. Referring to the IAU's definition as "sloppy," Metzger and his co-authors point out that no one else has separated asteroids from planets by using the clearing mandate. Planets, the paper argues, should not be held to dynamic descriptions of bodies that may change over time. "We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it's functionally useful," Metzger said in a statement. "It's a sloppy definition. They didn't say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit." Metzger is advocating instead for a planet obtaining its status due to being large enough to achieve a gravity-influenced spherical shape that activates geological changes. Speaking with CNN, IAU spokesperson Lars Lindberg Christensen indicated a motion could be put forward to have the group reevaluate the classification but that no one had yet done so. Whatever Pluto is or may one day become, it was a planet to Tombaugh, who wasn't around long enough to experience the reclassification. He died in 1997. In 2015, his ashes, attached to the New Horizons space probe, entered Pluto's orbit after nine years of travel. http://mentalfloss.com/article/556744/playing-tennis-linked-longer-life-span
Planet Nine may exist, but it might be hiding behind Neptune By Chris Ciaccia | Fox News Artist illustration of "Planet Nine," a hypothetical world about 10 times more massive than Earth. (Caltech/R. Hurt) Evidence for Planet Nine continues to mount, but there may be a good reason why scientists have yet to find it – it may be hiding. In October 2017, NASA released a statement saying that Planet Nine may be 20 times further from the Sun than Neptune is, going so far as to say "it is now harder to imagine our solar system without a Planet Nine than with one." But the reason it may not yet have been found is due to that same distance. At that distance, the equivalent, of 600 astronomical units (1 AU is defined as the distance between the Earth and the Sun, or approximately 93 million miles), it would be 160,000 times dimmer than Neptune is. Kevin Luhman, an astronomer at Pennsylvania State University, told Quanta Magazine by way of the Washington Post that at 1,000 AU, it's a "brick wall, basically," making any potential planet next to impossible to see using current technology. However, scientists believe the possibility of another planet, one which may have "10 times the mass of Earth," does indeed exist. “Every time we take a picture, there is this possibility that Planet Nine exists in the shot,” Surhud More, associate professor in Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo, told Quanta Magazine. Slashgear reports that it could take up to 1,000 years before the planet is found. Michael Brown from the California Institute of Technology has said he thinks “Planet Nine” will eventually be found, but it will take significantly stronger telescopes and planet finding technology than currently exist. In the Oct. 2017 statement, Caltech planetary astrophysicist Konstantin Batygin, who worked with Brown, said that there "five different lines of observational evidence" that point to the existence of the planet. The five lines of evidence are: Six known objects in the Kuiper Belt, all of which have elliptical orbits that point in the same direction. The orbits of the objects are all tilted the same way; 30 degrees "downward." Computer simulations that show there are more objects "tilted with respect to the solar plane." Planet Nine could be responsible for the tilt of the planets in our solar system; the plane of the planets orbit is tilted about 6 degrees compared to the Sun's equator Some objects from the Kuiper Belt orbit in the opposite direction from everything else in the solar system. "No other model can explain the weirdness of these high-inclination orbits," Batygin added. "It turns out that Planet Nine provides a natural avenue for their generation. These things have been twisted out of the solar system plane with help from Planet Nine and then scattered inward by Neptune." "If you were to remove this explanation and imagine Planet Nine does not exist, then you generate more problems than you solve," Batygin also said. "All of a sudden, you have five different puzzles, and you must come up with five different theories to explain them." Their work was published in a January 2016 paper that can be read in its entirety here. News of a Planet Nine first surfaced in 2014, when researchers found a planetoid and a subsequent celestial body that appears to orbit around the Sun. Follow Chris Ciaccia on Twitter @Chris_Ciaccia
It's a planet to me and always has been. When I was a small boy in Oswego, the local library had a contest to see who could read the most books. They posted all the heavenly solar system bodies, including the sun and our moon with colored paper cutouts on the highest part of the wall. Each contestant had a rocket ship cutout with some sort of ID on it. I think mine was a blue ship with my initials on it. Well, I read like a champ and won the contest. The last landmark was Pluto and I got there first. So, Pluto will always be a planet to me. By the way, I still think that was a great way to get a kid to read.
