July 15, 2016 Volume 22, Number 27 |
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A New Dwarf Planet Identified in Pluto's Neighborhood | |
New Dwarf Planet Discovered Far Beyond Pluto's Orbit Astronomers Discover Distant Dwarf Planet Beyond Neptune What is a Dwarf Planet? How many dwarf planets are there in the outer solar system? NOVA: Chasing Pluto New Dwarf Planet Beyond Pluto Hints At No Planet Nine On Monday, astronomers from the International Astronomical Union (IAU) announced the discovery of a new dwarf planet, temporarily dubbed 2015 RR245. 2015 RR245 resides in the Kuiper Belt, a ring of icy, rocky objects that orbit beyond Neptune. The Kuiper Belt's most famous resident is Pluto, which the IAU controversially reclassified from a "planet" to a "dwarf planet" in 2006. Pluto's reclassification centered on the IAU's decision to clarify that a planet must be powerful enough to "[clear] the neighborhood around its orbit," a criterion that Pluto does not meet. According to the IAU's definition of "dwarf planets," these celestial bodies must also have enough gravitational force to form a sphere, must orbit around the sun, and may not be satellites. Scientists are emphasizing that regardless of how we label Pluto and its neighbors, the discovery of 2015 RR245 provides us with significant new clues into the characteristics of the Kuiper Belt. Astronomers first identified 2015 RR245 in February of this year, when they examined images captured by a telescope in Hawaii as part of the Outer Solar System Origins Survey (OSSOS). Since Pluto's reclassification, five other dwarf planets have been identified in the Kuiper Belt, and astronomers believe that there will likely be more dwarf planet discoveries to come. [MMB] The first two links take readers to articles in Space and The Guardian, by Mike Wall and Ian Sample, respectively, that summarize what astronomers know about 2015 RR245 so far. Space also provides readers with an animation of 2015 RR245's 700 yearlong orbit. Next, readers will find a May 2016 article in Universe Today by Matt Williams that provides an overview of the IAU's decision to classify dwarf planets and what we currently know about other dwarf planets. Readers curious about potential future dwarf planet discoveries should check out the fourth link, which will take them to a page maintained by California Institute of Technology astronomy professor Mike Brown, who discovered dwarf planet Eris in 2005. (Second only to Pluto in size, Eris is the most massive of the known dwarf planets in the Kuiper Belt.) Brown provides readers with a detailed chart of objects identified in the Kuiper Belt and the likelihood, in Brown's view, that each object will be classified as a dwarf planet. The fifth link takes readers to a July 2015 PBS Nova episode, which details last year's New Horizon spacecraft mission. The New Horizon spacecraft took new, vivid photos of Pluto and provided additional clues about the Kuiper Belt. Finally, readers may recall recent speculation about the possible existence of a ninth planet beyond Neptune and the Kuiper Belt. Some scientists believe that the orbits of known dwarf planets may suggest the gravitational pull of a ninth planet. The final link takes readers to a recent Forbes article by Ethan Siegel, in which Siegel argues that the discovery of 2015 RR245 may point to an alternative hypothesis. Perhaps, Siegel writes, we have an incomplete view of how dwarf planets in the Kuiper Belt orbit the sun because astronomers and planetary scientists have only identified the nearest dwarf planets. Siegel argues that the 2015 RR245 discovery ought to "remind us all of how much more there is - not just in the Universe, but even in our Solar System - still left to discover." |