Eris and the Planet Definition War That Redrew Our Solar System

This video traces how a faint dot spotted during a Palomar survey grew into Eris, a distant world that sparked a crisis over what counts as a planet. It follows the Palomar team led by Mike Brown as they reexamine old data, the 2005 announcements that Haumea and Eris emerged, and the scramble to go public. It then explains the 2006 IAU vote that created a three part definition, which relegated Pluto to a dwarf planet and forced astronomy to rethink the solar system. The story ends with Eris in the scattered disc, its moon Dsnia, and the prospect of future missions to this icy frontier.

Discovery and the Palomar Survey

The Ashram video begins with a monumental inventory of the solar system and the dream of a 10th planet. At California's Palomar Observatory, a team led by Mike Brown, Chad Truo, and David Rabinowitz carried out a systematic search of trans Neptunian objects using the 1.2 meter Samuel Osin telescope. By rapidly photographing wide swaths of the sky and running automated software to flag moving objects, they uncovered a growing population of distant bodies such as Kuwa, Orcus, and Sedna. They hoped to find something bigger than Pluto, a planet that would complete a tidy 9 worlds picture, a belief Brown describes as a near inevitability. The search laid the groundwork for a discovery chain that would redefine the solar system.

The 2005 Scoops and the Eris Haumea Announcement

Brown's team had already flagged the possibility of a 10th world and decided to re‑examine data the software had previously passed over. On January 5, 2005, Brown clicked through a trio of images from October 21, 2003, and found a faint dot moving glacially against fixed stars. It appeared bright and distant, suggesting either a large size or high reflectivity, and it moved far more slowly than any prior TNO, marking it as an object from the solar system's edge. Provisionally designated 2003 UB 313, it signaled something significant—a genuine planetary candidate. The discovery coincided with a separate press wave in 2005 when another team announced Haumea, and Brown's group ultimately announced two major outer solar system bodies, Haumea and the object that would become Eris, on July 29, 2005. The secret had to surface, and the solar system would never be the same.

The IAU Debate and the Three Part Definition

In mythology, Eris is the goddess of strife, and the video links the 2005 discovery to a modern golden apple moment in astronomy. Early estimates suggested Eris might be larger than Pluto, and dynamical measurements of its moon implied it was about 27% more massive. If Eris is a planet, then Pluto’s status as a planet comes into question, along with other large trans Neptunian objects such as Machimake, Haumea, and Sedna. The IAU convened its 26th General Assembly in Prague in August 2006 to address the question of what counts as a planet. The assembly split into two camps: a geophysical definition based on hydrostatic equilibrium, and a dynamical one based on clearing the neighborhood of its orbit. The final decision favored the dynamical definition, leading to the 3 part resolution that a planet must orbit the Sun, be in hydrostatic equilibrium, and have cleared its neighbourhood. Pluto failed the third criterion and the IAU introduced a new category, the dwarf planet, for objects meeting the first two criteria but not the third. Pluto's reclassification left the solar system officially with eight planets, while Eris helped reveal a much larger and more complex cosmos.

Eris, Pluto, and the New Solar System Order

The video then traces the naming of Eris, selected by the discovery team in reference to the goddess of discord. The moon of Eris, Dysnomia, received a mythologically fitting name derived from lawlessness. The mass determination, made possible by tracking Dysnomia’s orbit with Kepler’s laws, confirmed Eris as more massive than Pluto, which intensified the debate about what constitutes a planet. The story emphasizes that Eris did not destroy Pluto but instead expanded our cosmic family, placing Pluto among the new dwarf-planet cohort and making clear that the solar system is not a simple, tidy hierarchy. The video also notes that Ceres gained a place among the newly defined dwarf planets, illustrating how the reclassification altered the entire architectural map of our solar system.

Eris’s Physical Secrets and a Moon’s Origins

Measurements from stellar occultations, including 2010 events, revealed Eris to have a diameter of about 2,326 kilometers, roughly the same size as Pluto but with a significantly higher density, around 2.43 grams per cubic centimeter versus Pluto’s 1.85. This implies Eris is rockier and denser, with a composition that differs from Pluto’s rock ice mix. Eris also has an exceptionally bright surface with an albedo near 0.99, likely due to frost and atmospheric processes that freeze on and off with its long, Sun‑distanced orbit. The video discusses the atmosphere, largely nitrogen and methane ice, which collapses into solid form at great distances from the Sun and sublimates again as Eris moves closer to the center. James Webb observations have added layers of complexity, suggesting methane isotope variations that may hint at geothermal processes beneath Eris’s rocky core. A moon accompanies Eris, and its origin is traced to a colossal collisional event, analogous to the formation of Earth’s Moon, that blasted material into orbit around Eris, creating a dark, rocky satellite that is tidally locked to its parent.

Eris’s Orbit, the Scattered Disc, and the Bigger Picture

The video illustrates Eris’s unusual orbit: a mighty ellipse taking 557 Earth years to complete, with a perihelion around 38 astronomical units and an aphelion near 98 AU. Its orbit is steeply inclined, about 44 degrees to the ecliptic, causing Eris to swing high above and plunge below the orbital plane. For years, Eris was thought to be Pluto’s larger twin, but the 2010 occultation and subsequent measurements clarified differences in density and mass, cementing Eris’s status as a prominent trans Neptunian object in the scattered disc rather than in the main Kuiper Belt. The video emphasizes that Eris’s discovery broadened the solar system beyond eight planets and introduced a vast population of distant icy worlds. It also notes that New Horizons provided a vivid portrait of Pluto, while Eris remains a distant, largely unexplored world that may eventually be the subject of a dedicated mission, potentially decades from now. In the meantime, the solar system is recognized as an architecture of inner rocky planets, outer giants, and a sprawling, still mostly unseen belt of icy bodies that extend the frontier of human exploration.

Conclusion: A Universe Remapped, a Frontier Unfolding

The final messages stress that the Eris revelation did not terminate curiosity but expanded it. The video closes by reflecting on the new vantage point the planetary definition war provided; it underscored that scientific progress often lies not in final answers but in reframing questions and widening horizons. Eris’s story is presented as a powerful example of how discovery can destabilize existing classifications while advancing a richer, more coherent understanding of our cosmic neighborhood. The screen wraps with a nod to the ongoing exploration of the solar system and the promise of future missions to Eris and the scattered disc frontier.