594913 ꞌAylóꞌchaxnim (

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been cal ...

) is a large near-Earth asteroid discovered by the

Zwicky Transient Facility The Zwicky Transient Facility (ZTF, obs. code: I41) is a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at the Palomar Observatory in California, United States. Commissioned in 2018, it supersedes ...

on 4 January 2020. It is the first asteroid discovered to have an orbit completely within

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

's orbit, and is thus the first and only known member of the eponymous ꞌAylóꞌchaxnim (informally named Vatira before its discovery) population of Atira-class asteroids. ꞌAylóꞌchaxnim has the smallest known

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

and third-smallest known semi-major axis among all asteroids. With an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

approximately 16.2, the asteroid is expected to be larger than in diameter.

Discovery

ꞌAylóꞌchaxnim was discovered by the

(ZTF) survey at the Palomar Observatory on 4 January 2020, by astronomers Bryce Bolin, Frank Masci, and Quanzhi Ye. The discovery formed part of a campaign for detecting interior-Earth asteroids (Atiras) using the wide-field ZTF camera on the 1.22-meter

Samuel Oschin telescope The Samuel Oschin telescope, also called the Oschin Schmidt, is a Schmidt camera at the Palomar Observatory in northern San Diego County, California. It consists of a 49.75-inch Schmidt corrector plate and a 72-inch (f/2.5) mirror. The instrument ...

at the Palomar Observatory. The detection of such objects is difficult due to their close proximity to the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

: asteroids within the orbit of

never reach solar elongations greater than 47 degrees, meaning that they are only observable during

twilight Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this i ...

as the Sun is below the Earth's horizon. Because of this, inner-Venusian asteroids could only be observed within a short time frame, hence why the ZTF camera was used since it can effectively detect transient objects. At the time of discovery, ꞌAylóꞌchaxnim was located in the constellation

Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainme ...

, at an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

around 18. The discovery of ꞌAylóꞌchaxnim was reported by astronomer Bryce Bolin, and was subsequently listed on the Minor Planet Center's

Near-Earth Object Confirmation Page The Near-Earth Object Confirmation Page (NEOCP) is a web service listing recently-submitted observations of objects that may be near-Earth objects (NEOs). It is a service of the Minor Planet Center (MPC), which is the official international archiv ...

(NEOCP) on 4 January 2020. Follow-up observations were then conducted at various observatories in order to determine the asteroid's orbit based on its orbital motion. The discovery of the asteroid was then formally announced in a

Minor Planet Electronic Circular The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Function T ...

issued by the MPC on 8 January 2020. Follow-up observations were later conducted in November 2020 by the Palomar and Xingming observatories, reducing ꞌAylóꞌchaxnim's uncertainty parameter to 5. Prior to the discovery of ꞌAylóꞌchaxnim, co-discoverer Quanzhi Ye and colleagues had predicted in December 2019 that the ZTF would detect its first Vatira asteroid within Venus's orbit shortly after the discoveries of several small-

asteroids including and . Given the difficulty of detecting such asteroids at small solar elongations, they estimated that at least one additional Vatira asteroid will be detected by the ZTF.

Nomenclature

Upon discovery, the asteroid was given the internal designation ZTF09k5. The Minor Planet Center (MPC) gave it the

on 8 January 2020, after follow-up observations sufficiently determined its orbit. After its orbit had been determined to sufficient precision, the MPC assigned it the permanent number 594913 on 20 September 2021 (). Its name was approved on 8 November 2021.WGSBN Bulletin 1, #11
/ref> means 'Venus girl' in the indigenous

Luiseño language The Luiseño language is a Uto-Aztecan language of California spoken by the Luiseño, a Native American people who at the time of first contact with the Spanish in the 16th century inhabited the coastal area of southern California, ranging fr ...

of southern California. The name celebrates the location of the discovery (Palomar Mountain, which is on ancestral Luiseño land) and the fact that ꞌAylóꞌchaxnim is the first discovered asteroid to orbit entirely within the orbit of Venus. Being the prototype of the informally named Vatira class, its name is expected to be used to refer to this newly confirmed population.

Orbit and classification

ꞌAylóꞌchaxnim is the only asteroid known to have an orbit completely within Venus's orbit. With an

distance of approximately 0.654

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...

s (AU), it has the smallest known aphelion of all asteroids. In comparison, Venus's average orbital distance from the Sun is 0.723 AU, with a

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

distance of 0.718 AU. ꞌAylóꞌchaxnim is formally classified as an Atira asteroid by the Minor Planet Center due it having an orbit within that of

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. However, unlike previously known Atira asteroids, ꞌAylóꞌchaxnim's orbit is contained within that of Venus, thus it falls into the proposed category of Vatira asteroids—a subclass of Atira asteroids with aphelion distances less than Venus's perihelion distance (hence the name: a

portmanteau A portmanteau word, or portmanteau (, ) is a blend of words ꞌAylóꞌchaxnim is technically classified as a

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

under the Atira classification, though the asteroid's

minimum orbit intersection distance Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits o ...

from Earth is . The orbit of is a well-secured with an

uncertainty parameter The uncertainty parameter ''U'' is introduced by the Minor Planet Center (MPC) to quantify the uncertainty of a perturbed orbital solution for a minor planet. The parameter is a logarithmic scale from 0 to 9 that measures the anticipated longit ...

of 2. The asteroid orbits the Sun in approximately 151 days (0.41 years), with a semi-major axis of approximately 0.5554 AU. 's orbit is close to a 3:2 mean-motion orbital resonance with Venus, meaning that ꞌAylóꞌchaxnim completes approximately three orbits for every two orbits completed by Venus. The orbit of ꞌAylóꞌchaxnim is moderately eccentric, as it approaches only 0.457 AU from the Sun at perihelion, just within Mercury's aphelion distance of 0.467 AU. ꞌAylóꞌchaxnim's orbit is also moderately inclined to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...

by approximately 15.9 degrees. ꞌAylóꞌchaxnim has a smaller orbital eccentricity and inclination compared to the generally expected values for typical Vatira asteroids, which were predicted to have an eccentricity around 0.4 and an inclination around 25 degrees. The asteroid's minimum orbit intersection distance from Mercury and Venus is about and , respectively. ꞌAylóꞌchaxnim is approximately tied with (0.5553 AU) as having the second-smallest known orbital period and semi-major axis among all asteroids, though has a slightly smaller semi-major axis. In this case, ꞌAylóꞌchaxnim has the third-smallest known semi-major axis among all asteroids.

Orbital dynamics

ꞌAylóꞌchaxnim had likely originated from the main

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, c ...

, where its orbit was locked in a

secular resonance A secular resonance is a type of orbital resonance between two bodies with synchronized precessional frequencies. In celestial mechanics, secular refers to the long-term motion of a system, and resonance is periods or frequencies being a simple n ...

that caused its orbital eccentricity to gradually increase over time, evolving onto an Earth-crossing orbit. Subsequent close encounters with Earth, Venus, and Mercury resulted in gravitational

perturbation Perturbation or perturb may refer to: * Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly * Perturbation (geology), changes in the nature of alluvial deposits over time * Perturbat ...

s of the asteroid's orbit, reducing its momentum and causing it to orbit closer to the Sun. Such inward orbital migration of objects is thought to be rare. Near-Earth asteroids transitioning into the Vatira region often have unstable, short-term orbits due to frequent gravitational perturbations by Venus and Mercury. ꞌAylóꞌchaxnim rarely crosses the orbits of Mercury and Venus, which reduces the number of close encounters with either planet that would otherwise perturb ꞌAylóꞌchaxnim's orbit. Nevertheless its orbit is likely to be stable for less than a million years, unless it is on (or enters soon) a nearby 3:2

mean-motion resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Venus, which could extend its stability to a few million years. Dynamical modeling of ꞌAylóꞌchaxnim's orbit show that the most likely scenario for its orbital evolution is that ꞌAylóꞌchaxnim's orbit will oscillate for several millions of years before gravitational perturbations lead to the asteroid's eventual collision with a planet, most likely Venus. At 140 thousand years from the present, ꞌAylóꞌchaxnim's aphelion distance will exceed Venus's perihelion distance, as a result of the combined effects of the Kozai resonance and gravitational perturbations. Within the Vatira region, the Kozai resonance causes the orbital inclinations and eccentricities of asteroids to oscillate over several millions of years. As a result, Vatira asteroids can become Atira-class asteroids and vice versa over time, and can cross the orbits of Mercury and Venus during these orbital oscillations. The Kozai resonance often disrupts the orbits of Vatira asteroids, albeit it can also lead to orbital stability for some unperturbed Vatira asteroids. At about 1.2 million years from the present, ꞌAylóꞌchaxnim will leave the Vatira region and will transition onto a Mercury-crossing orbit, with its perihelion oscillating around Mercury's aphelion distance before decoupling from the planet's orbit at about 2.1 million years. After decoupling from Mercury's orbit, ꞌAylóꞌchaxnim was shown to oscillate between an Atira-type orbit ( Q < 0.983 AU) and an Earth-crossing

Aten Aten also Aton, Atonu, or Itn ( egy, jtn, ''reconstructed'' ) was the focus of Atenism, the religious system established in ancient Egypt by the Eighteenth Dynasty pharaoh Akhenaten. The Aten was the disc of the sun and originally an aspect o ...

-type orbit (Q > 0.983 AU), in which the asteroid's aphelion oscillates around Earth's perihelion distance of 0.983 AU. About 740 thousand years afterward, ꞌAylóꞌchaxnim will likely return to its Mercury-crossing orbit, though gravitational perturbations by Mercury and Venus will scatter it onto an Earth-crossing orbit once more before colliding with either planet. At about 4.1 million years from the present, ꞌAylóꞌchaxnim will most likely collide with Venus.

Physical characteristics

ꞌAylóꞌchaxnim is estimated to have an absolute magnitude (H) approximately 16.2. The medium diameter of ꞌAylóꞌchaxnim is expected to be larger than . Assuming that the

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...

is between 0.25 and 0.05, its diameter should be around , respectively. Near-Earth asteroid population models predict that at least one asteroid of this size has an orbit within that of Venus, implying that ꞌAylóꞌchaxnim could be one of the largest members of the Vatira population. Visible and

near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

spectroscopy by the

Roque de los Muchachos Observatory Roque de los Muchachos Observatory ( es, Observatorio del Roque de los Muchachos, ORM) is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands, Spain. The observatory site is operated b ...

in 2020 suggests that ꞌAylóꞌchaxnim has a reddish surface that is

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

-rich, based on the presence of a 1 μm absorption feature characteristic of

S-type asteroid S-type asteroids are asteroids with a spectral type that is indicative of a siliceous (i.e. stony) mineralogical composition, hence the name. They have relatively high density. Approximately 17% of asteroids are of this type, making it the secon ...

s. The abundance of olivine in the surface of ꞌAylóꞌchaxnim suggests that it could be a mantle asteroid formed as a fragment from the rocky mantles of large, internally differentiated bodies. The absorption features in ꞌAylóꞌchaxnim's spectrum appear to be intermediate between the S-type and A-type spectral classes, hence it is classified as an Sa-type asteroid. Assuming an average albedo of 0.22 for S-type asteroids, ꞌAylóꞌchaxnim's diameter can be constrained to approximately .

Notes

References

External links

2020 AV2, the first intervenusian asteroid ever discovered

Gianluca Masi Gianluca Masi (born 22 January 1972) is an Italian astrophysicist and astronomer, as well as a discoverer of minor planets and variable stars. Scientific career He started his interest in astronomy in childhood, later becoming a professional ...

, ''The Virtual Telescope Project 2.0'', 9 Jan 2020
Meet 2020 AV2, the first asteroid found that stays inside Venus's orbit!
by

Phil Plait Philip Cary Plait (born September 30, 1964), also known as The Bad Astronomer, is an American astronomer, skeptic, and popular science blogger. Plait has worked as part of the Hubble Space Telescope team, images and spectra of astronomical objec ...

, 10 Jan 2020
Meet 2020 AV2, the 1st asteroid entirely within the orbit of Venus
by Gianluca Masi, 10 Jan 2020
First asteroid found within Venus's orbit could be a clue to missing 'mantle' asteroids
Nola Redd, ''

Science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

'', 1 July 2020 * * {{DEFAULTSORT:594913 Atira asteroids Discoveries by the Zwicky Transient Facility Aylochaxnim # 20200104 20200104