Is it “sorta, kinda moon in a sorta, kinda orbit around Earth…[a] quasi-moon…an artifact of the actual moon…a quasi-satellite…”? Could it be an asteroid, a co-orbital asteroid?
These are the “sorta” terms that have been used for the past five years when discussing quasi-satellite (469219), provisionally designated 2016 HO3.
Discovered at the Haleakala Observatory in Hawaii in April 2016, the “co-orbital asteroid” is more elegantly and appropriately known as “Kamo’oalewa,” a Hawaiian word that “refers to an oscillating celestial object.”
The name Kamo’oalewa it is derived from . the Hawaiian words ka ‘the’, mo’o ‘fragment’, referring to it being a piece broken off a larger object, a ‘of’, and lewa ‘to oscillate’, referring to its motion in the sky as viewed from Earth.
Chris Melore at Hawaii’s KHON2.com more romantically ascribes the name to a “Hawaiian creation chant, which describes an offspring who travels on its own.”
Numerous scientific papers and articles have been written about Kamo’oalewa, its perceived origins and composition, its orbit, its “dynamical lifetime,” etc.
One of them is by Ben Sharkey, a graduate student of the Lunar and Planetary Laboratory at the University of Arizona who, along with nine colleagues, recently published a scientific paper on Kamo’oalewa in the journal Nature.
Using the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT), both located in Arizona, Sharkey et al are attempting to solve the mystery of Kamo’oalewa’s origins.
The paper is chock full of scientific terms and data far above this author’s paygrade, but which, I am sure, others will appreciate.
…the orbit of Kamo’oalewa is very Earth-like, with semi-major axis within 0.001 au of Earth’s, a low eccentricity of just ~0.1, and a modest inclination of about 8 degrees to the ecliptic…As it orbits the Sun with a ~1 year orbital period, it takes a quasi-satellite path relative to Earth, that is, it makes retrograde loops around Earth with a ~1 year period but well beyond Earth’s Hill sphere.
In TIME’s “Earth Has a Second Moon—For Another 300 Years, At Least,” Jeffrey Kluger describes the orbit in layman’s terms. “A repeating corkscrew-like trajectory” he calls it. In the same article, Sharkey abandons all scientific talk and calls Kamo’oalewa‘s orbit a “sort of a dance.”
As for Kamo’oalewa’s origins, Sharkey poses three possibilities:
• Kamo’oalewa was “captured in its Earth-like orbit from the general population of NEOs” (near-Earth objects).
• It originates from an “as-yet undiscovered quasi-stable population of Earth’s Trojan asteroids. “(Asteroids that orbit the Sun at the same orbital distance as Jupiter)
• Kamo’oalewa originates in our own Earth-Moon system, either as “impact ejecta” from the lunar surface or “as a fragment of a parent NEO’s tidal or rotational break up during a close encounter with Earth-Moon.”
Supported by spectral analysis of Kamo’oalewa’s composition (“[we] conclude that the best match is with lunar-like silicates,”) its orbital characteristics (e.g., low relative velocity value during its close approaches to Earth-Moon), and other factors, Sharkey and his colleagues put their money on the “lunar ejecta” hypothesis, raising the prospect that Kamo’oalewa comprises lunar material.
Finally, on Kamo’oalewa’s life expectancy:
Sharkey finds that Kamo’oalewa’s “quasi-satellite motion” (its “dynamical lifetime”) began approximately 100 years ago and that it will continue to be our and the moon’s companion for approximately 300 more years.
After that, Kluger says, “[Kamo’oalewa] will break free of its current gravitational chains and twirl off into the void…spend the rest of its long life traveling on its own…” true to the Hawaiian creation chant.
Before the Ferris wheel-size asteroid wanders off into the infinity of space, however, there is at least one space agency that would like to “touch and feel” Kamo’oalewa. According to Wikipedia, the China National Space Administration is planning a robotic mission to Kamo’oalewa in 2025 to retrieve and return to earth samples from the quasi-satellite.
For those who have sorta Large Binocular Telescope or kinda Lowell Discovery Telescope, the best time to “view” Kamo’oalewa is in April when, according to Sharkey, Kamo’oalewa “becomes bright enough…to be characterized by large telescopes on Earth.”
Should your telescope not be quite ready this coming April, don’t worry, there will be 299 more opportunities.
Note: In the lead animation: Earth is blue dot · Kamo’oalewa’s trajectory in purple
For more related animations click HERE
The author is a retired U.S. Air Force officer and a writer.