Sednoid

A sednoid is a <a href="/facts/Trans-Neptunian_object/oF5vsbz9">trans-Neptunian object</a> with a large <a href="/facts/Semi-major_axis/l7JES2wo">semi-major axis</a> and a high <a href="/facts/Perihelion/VaL6ow9w">perihelion</a>, similar to the orbit of the <a href="/facts/Sedna_(dwarf_planet)/6aXuaYoM">dwarf planet Sedna</a>. The consensus among astronomers is that there are only four objects that are known from this population: Sedna, <a href="/facts/2012_VP113/Iazcyab7">2012 VP113</a>, <a href="/facts/541132_Lele%25C4%2581k%25C5%25ABhonua/06cRL8Qk">541132 Leleākūhonua</a> (2015 TG387), and 2023 KQ14. All four have perihelia greater than 60 AU. These objects lie outside an apparently nearly empty gap in the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a> and have no significant interaction with the planets. They are usually grouped[by whom?] with the <a href="/facts/Detached_object/bwVNIdQq">detached objects</a>. Some astronomers consider the sednoids to be Inner Oort Cloud (IOC) objects, though the <a href="/facts/Hills_cloud/gQDyNasP">inner Oort cloud</a>, or <a href="/facts/Hills_cloud/gQDyNasP">Hills cloud</a>, was originally predicted to lie beyond 2,000 AU, beyond the aphelia of the known sednoids.
One attempt at a precise definition of sednoids is any body with a <a href="/facts/Perihelion_and_aphelion/VaL6ow9w">perihelion</a> greater than 50 AU and a <a href="/facts/Semi-major_axis/l7JES2wo">semi-major axis</a> greater than 150 AU.
However, this definition applies to the objects <a href="/facts/2013_SY99/hcu0H09A">2013 SY99</a>, 2020 MQ53, and <a href="/facts/2021_RR205/7dSRupfH">2021 RR205</a> which have perihelia beyond 50 AU and semi-major axes over 700 AU. Despite this, these objects are thought[by whom?] to not belong to the sednoids, but rather to the same dynamical class[which?] as <a href="/facts/474640_Alicanto/TFhl9gQS">474640 Alicanto</a>, <a href="/facts/2014_SR349/VLWTCwjh">2014 SR349</a> and <a href="/facts/2010_GB174/zaMKq8e9">2010 GB174</a>.
With their high eccentricities (greater than 0.8), sednoids are distinguished from the high-perihelion objects with moderate eccentricities that are in a stable resonance with Neptune, namely <a href="/facts/2015_KQ174/CEfpvxTc">2015 KQ174</a>, <a href="/facts/2015_FJ345/F7mhdreC">2015 FJ345</a>, <a href="/facts/(612911)_2004_XR190/yQqRHkU9">(612911) 2004 XR190</a> ("Buffy"), <a href="/facts/(690420)_2014_FC72/TwMKKUcv">(690420) 2014 FC72</a> and <a href="/facts/2014_FZ71/TYt6Pcrn">2014 FZ71</a>.

Sednoid open-in-new

Sednoid