New dwarf planet just dropped

Currently, the solar system is home to five officially recognized dwarf planets, Ceres, Eris, Haumea, Makemake, and Pluto. Each of them is pretty interesting and unique from the others. However, though these are the only objects officially recognized as dwarf planets by the IAU, they are not the only objects in the solar system that are likely to be dwarf planets. The definition of a dwarf planet is simply an object that hasn't cleared its orbit but is massive enough to be rounded under its own gravity, or in other words, be in hydrostatic equilibrium. Under this definition, it's likely that several additional objects qualify as dwarf planets, Quaoar, Sedna, Orcus, Charon, Gonggong, Salacia, Aya, and Mani, and potentially more depending on where you draw the line. These objects aren't yet considered official dwarf planets because it's still technically not confirmed they are 100% in hydrostatic equilibrium, as that depends on not only their physical sizes, many of which aren't known with a good amount of precision, as well as unknown factors about their compositions. But dwarf planets or not, all of these worlds are super interesting. Quaoar and Haumea both host ring systems and large moons, and Haumea is spinning incredibly fast, potentially due to a collision. Pluto has active cryovolcanism and a thin atmosphere. Observations of Mani suggest, though this is not confirmed, that it may possess a mountain or crater rim that is 25 kilometers tall, which would make it the largest known mountain in the solar system. Ceres has surface features covered in salt that may have been formed by brine being released through hydrothermal activity. Sedna's orbit is so long and eccentric that at the furthest point of its orbit, it exits the heliopause and is exposed to radiation from from interstellar space. Point is, these worlds are all weird and unique, and there's likely dozens of them in the outer solar system, many of which still haven't even been discovered. The Kuiper Belt scattered disk and the gap between them and the Oort Cloud is very large, and there's potentially dozens to hundreds of new dwarf planets in this region that are currently too dark to be seen. You may have heard this before, but several additional Pluto-sized objects, and potentially, though there's no direct evidence for this, objects up to the size of Mars may be in this area not yet able to be detected, but that's a subject for another video. This video will be about the largest new object in the outer solar system discovered in recent memory, which is likely to be the solar system's newest dwarf planet candidate, 2026 ED 138. We'll talk about everything we know about this new Outer Solar System object, and also how it was missed despite having a visibility similar to previously discovered objects like Quaoar or Orcus, and what it means for future discoveries. So let's get into it. 2026 ED-138's discovery was reported in October of this year, and it's the brightest solar system object as viewed from Earth discovered since 2013, where it's dethroning Chimney Gagwa. It's also, as of the time I'm making this video, the brightest solar system object without a confirmed size. This is because so far we only know this object exists because of the light it's reflecting from the sun being visible, but different materials have different reflectivities. However, we do know a few constraints. Based on its brightness, 2026 ED-138 must have a diameter between 600 and 1,500 kilometers. Or, in other words, it could be as large as Haumea or as small as Eris's moon Dysnomia. If the object's surface is made of darker materials, it must be larger in size to produce the same observations. However, these constraints are based on what's physically possible, not necessarily what's likely. Based on the compositions of other Kuiper Belt objects, It's possible to constrain these numbers further. The authors of the paper Discovering 2026 ED 138 suggest a likely diameter of between 610 and 970 kilometers, taking this object's possible maximum size down from around Haumea or Eris to about Ceres. So it's probably not one of the largest KBOs ever found, but potentially similar to Orcus, Sedna, Salacia, or Varda. So far, 2026 ED-138's composition is not known with certainty. However, these initial observations suggest it's likely somewhat reddish in color, a trend seen with many other Kuiper Belt objects like Pluto or Makemake. What is known with more certainty, however, is this object's orbit. Initial observations suggest it takes about 283 years to orbit the Sun, with an eccentricity of about 0.14. It gets as close to the Sun as 37.11 AU and as far out as 49.07, meaning it never gets closer to the Sun than Neptune. It is also worth noting that 2026 ED138's orbit shares some notable similarities with the with the Haumea Collisional family. As mentioned earlier, Haumea's oblate shape and fast spin may have been caused by a collision in its past. There's additional evidence for this collision across the Kuiper Belt, as Haumea is surrounded by a family of compositionally similar objects on similar orbits, indicating they may have all once been part of an original progenitor body that was shattered. The Haumea family is in a 7-12 orbital resonance with the planet Neptune, which 2026 ED-138 seems to tentatively be in as well. However, initial observations show the 2026 ED138 is likely different in composition from the Haumea family, different enough to suggest it's not a true member of the Collisional family, but rather shares a similar orbit just by coincidence. Regardless, like lots of KBOs, this world's orbit suggests it has been gravitationally influenced by Neptune, due to its large orbital inclination of 25 degrees off the ecliptic and moderate eccentricity. It's likely that during the formation of the solar system, this object was forced off of its original circular orbit by the formation and migration of Neptune, giving it the orbit we see today. So 2026 ED 138 is not much further from the sun than other dwarf planet candidates of its size. It's on average about 43 AU away from the sun. For comparison, Sedna, which is on the larger end of this object's maximum estimated size, is about 83 AU away right now. The large Kuiper Belt Object Ixion, on the lower end of this object's size estimate, is a similar distance away from the Sun as this one. So this begs the question of why 2026 ED138 was missed for so long, and why it wasn't found sooner given its in its similarities to other KBOs that were detected years or even decades ago. There's a pretty simple explanation for this. Currently, 2026 ED 138 is close to the galactic plane in the sky, where there's more stars and dust, making it harder to pick out individual solar system objects. Not only that, but its declination, how far away it is from the celestial equator, is very far south, and most sky surveys don't look in this area. So it makes sense it was missed, it's just in a part of the sky that's difficult to find things in. However, because it's orbiting the Sun, 2026 ED 138 wasn't always in this area. One of the most useful ways to find out an object's orbit after it was discovered is to look through earlier telescope data to see if it appears in any earlier images where it was missed. Such images have been found for 2026 ED 138, and they go back pretty far. After looking through old data, it was found that 2026 ED-138 actually appeared in telescope images dating back to as early as 1937, only seven years after the discovery of Pluto. For comparison, the earliest recovery image, or image taken of it before he realized what it was, of Haumea dates back to 1955, and the earliest of Eris was in 1954. This also means that 2026 ED 138 has the longest observation arc, or amount of time we've been looking at it, albeit unknowingly, of any Kuiper Belt object other than Pluto. So though this object was officially discovered in 2026, it's been accidentally captured in telescope images for almost a century now, and only just now did modern observations show what it was. This, of course, raises the question of what other large dwarf planet candidates in the outer solar system we may be missing. 2026 ED138, assuming its true size is close to the maximum estimate, is in the top 10 largest Kuiper Belt objects ever discovered, and the fact that it was only discovered this year suggests there could be many other large to medium-sized KBOs hiding in the light of the galactic plane that are still waiting to be discovered. Not to mention potentially additional planets, like Planet 9, which is something I definitely need to make a full video I'll see you in the next video about soon. We don't know much about 2026 ED 138 yet. It does show us the Kuiper Belt is still a largely unexplored region, and there could literally be hundreds of small worlds out here that we haven't found yet. And as we've seen with our current dwarf planets, with their moon and ring systems and interesting surface features, there's a lot of cool stuff to find out here. Hopefully we can learn more about the Kuiper Belt and its many poorly explored worlds soon. Thank you for watching. If you enjoyed, check out my other videos about exoplanets and space exploration.