594913 ꞌAylóꞌchaxnim

• 1. Introduction

  ›

  594913 ꞌAylóꞌchaxnim orbits the Sun in a place no asteroid had ever been confirmed to reach: entirely inside the orbit of Venus. On the 4th of January 2020, a wide-field camera at Palomar Observatory caught a faint smudge drifting through the constellation Aquarius at apparent magnitude 18, barely bright enough to detect. Three astronomers, Bryce Bolin, Frank Masci, and Quanzhi Ye, were hunting for exactly this kind of object. What they found answered a long-standing question about whether any asteroid could survive so deep inside the inner Solar System. It also raised a harder one: how did it get there, and how long can it stay?

• 2. A Name from the Land Beneath the Telescope

  ›

  Palomar Mountain sits on ancestral territory of the Luiseño people of southern California. When the time came to name the newly confirmed asteroid, that geography shaped the choice. ꞌAylóꞌchaxnim means 'Venus girl' in the Luiseño language, a name approved on the 8th of November 2021. The permanent catalog number 594913 had been assigned by the Minor Planet Center on the 20th of September 2021, following a formal process that began with an internal ZTF designation, ZTF09k5, and then a provisional designation issued on the 8th of January 2020. Because ꞌAylóꞌchaxnim is the first confirmed member of its orbital class, its name is now expected to replace the informal placeholder 'Vatira' as the defining label for the entire population.

• 3. The Twilight Hunt

  ›

  Asteroids with orbits inside Venus's path never stray more than 47 degrees from the Sun as seen from Earth. That constraint traps them in perpetual twilight: the only window to observe them is the brief interval after sunset or before sunrise, when the Sun is just below the horizon. The Zwicky Transient Facility camera on the 1.22-meter Samuel Oschin telescope at Palomar was chosen for this campaign precisely because it excels at detecting fast-moving, transient objects in short exposure windows. After the initial detection was listed on the Minor Planet Center's Near-Earth Object Confirmation Page on the 4th of January 2020, follow-up observations at multiple observatories refined the orbit. A second round of follow-up in November 2020 at the Palomar and Xingming observatories reduced the uncertainty parameter to 5, and subsequent work brought it down to 2.

• 4. An Orbit Unlike Any Other

  ›

  ꞌAylóꞌchaxnim's aphelion, the farthest point in its orbit from the Sun, reaches only 0.654 astronomical units. Venus's perihelion, the closest Venus itself gets to the Sun, is 0.718 AU. The asteroid never gets close to Venus's lane. Its semi-major axis measures approximately 0.5554 AU, making it approximately tied with one other object for the second-smallest known among all asteroids, with a slightly smaller rival holding third place for ꞌAylóꞌchaxnim. One full trip around the Sun takes about 151 days, or 0.41 years. At its closest approach to the Sun, perihelion, the asteroid dips to roughly 0.457 AU, just inside Mercury's own aphelion distance of 0.467 AU. Its orbit is inclined roughly 15.9 degrees to the ecliptic. Both values are milder than the eccentricity near 0.4 and inclination near 25 degrees that theorists had predicted for typical members of this class.

• 5. A Rocky Traveler from the Main Belt

  ›

  ꞌAylóꞌchaxnim almost certainly did not form where it now orbits. Dynamical models point to the main asteroid belt as its birthplace. A secular resonance there gradually pumped up the asteroid's orbital eccentricity over time until it crossed Earth's path. Close gravitational encounters with Earth, Venus, and Mercury then bled off orbital momentum and pushed the object inward. Such deep inward migration is considered rare. The asteroid's current orbit rarely crosses those of Mercury and Venus, which limits the disruptive gravitational encounters that usually destabilize objects in this region. Still, the orbit is not permanent. Modeling shows that at roughly 140 thousand years from now, ꞌAylóꞌchaxnim's aphelion will exceed Venus's perihelion distance under the combined influence of the Kozai resonance and gravitational perturbations, temporarily exiting the Vatira zone.

• 6. A Fate Written in Gravity

  ›

  At about 1.2 million years from the present, ꞌAylóꞌchaxnim will transition onto a Mercury-crossing orbit, with its perihelion oscillating near Mercury's aphelion before decoupling from that planet's gravitational influence at roughly 2.1 million years. After decoupling, the asteroid will swing between an Atira-type orbit and an Earth-crossing Aten-type orbit, its aphelion oscillating around Earth's perihelion distance of 0.983 AU. About 740 thousand years after that phase, gravitational scattering by Mercury and Venus will redirect the asteroid again. The most probable long-term outcome, according to dynamical modeling, is a collision with Venus within 10 million years. The Kozai resonance, which governs the oscillation of orbital inclinations and eccentricities for objects in the Vatira region, can either accelerate this fate or, for some unperturbed cases, extend orbital stability to a few million years.

• 7. Surface of an Ancient Fragment

  ›

  Spectroscopy conducted at the Roque de los Muchachos Observatory in 2020 revealed a reddish surface dominated by olivine. The spectrum carries a 1-micrometer absorption feature characteristic of S-type asteroids, though the absorption features fall between S-type and A-type classifications, placing ꞌAylóꞌchaxnim in the Sa spectral subclass. The high olivine content is a telling clue: it suggests the asteroid may be a fragment from the rocky mantle of a large, internally differentiated parent body that broke apart long ago. Assuming an average albedo of 0.22 for S-type asteroids, the diameter can be constrained from the absolute magnitude of approximately 16.2. Population models predict that at least one asteroid of this size should exist with an orbit inside Venus, hinting that ꞌAylóꞌchaxnim could be among the larger members of a Vatira population whose full census remains entirely unknown.