Discovery and Naming of the Near-Earth Asteroid 199145
The asteroid designated 199145 (2005 YY128) was first spotted in 2005. This twofold naming reflects the rules used by astronomers to catalog minor planets and their histories of observation.
When an asteroid approaching Earth is seen for a second time, during its second opposition, it receives a permanent number. In this case, the number is 199145. The discoverers then have the opportunity to propose a formal name, often drawing from mythology, geography, or notable individuals who are no longer living, to avoid honoring someone who is still living, as explained by astronomer Voropaev.
Assigning a permanent number is not immediate. It takes time because the asteroid’s orbit must be precisely determined. Most asteroids are faint and can only be tracked during opposition, when Earth lies between the Sun and the object. If the body is not bright enough, observers may lose sight of it, and the available observing window may be too short to nail down the orbit. In such cases, a second set of observations is needed in the next opposition before cataloging proceeds.
199145 is a near-Earth asteroid, yet its proximity to Earth is not constant; its orbit crosses Earth’s path. Classified as an Apollo asteroid, it poses a potential danger if its trajectory brings it close to our planet. Its orbit shows a perihelion near the Sun where it crosses Mercury’s zone, while its aphelion lies between Mars and Jupiter, tracing a long, oval path that completes a cycle roughly every two years or 774 days.
Current knowledge about its composition and internal structure remains limited, and its diameter is only approximate, estimated between 500 and 800 meters. From Earth, it appears as a point of light rather than a measurable disk, since most telescopes cannot resolve its angular size with precision.
Estimates of its size rely on brightness and an assumed average reflectivity, or albedo, similar to that of objects with comparable compositions. Albedo varies widely among asteroids: some are very dark like carbonaceous bodies, while others in the Vesta family reflect a great deal of light. With these assumptions, the size estimate for 199145 centers around 800 meters, though a brighter surface would suggest a smaller diameter and a darker surface could imply a larger one.
Experts note that if the asteroid were white rather than gray, a diameter near 400 meters might be expected; a darker object could exceed a kilometer in size. Such a high estimate would be unusually large for its class, and scientists expect that several thousand near-Earth objects will accompany our planet in similar approaches. A direct impact would release energy comparable to the detonation of a very large thermonuclear device, far exceeding the energy seen in the Chelyabinsk event, which caused shock waves and structural damage with a far smaller object.
Even without a precise size, a hypothetical impact energy can be enormous. A calculator used by Imperial College London estimates that if 199145 were to strike Earth, the energy could reach tens of thousands of megatons of TNT, far beyond historical explosions. Such an event would create a large crater and seismic effects spanning hundreds of kilometers, underscoring why even distant approaches are carefully monitored.
Despite these dramatic possibilities, current calculations indicate no imminent danger to Earth. Preliminary studies suggest that over the next two centuries no dangerous approach is expected, with the closest approach projected at several million kilometers. After successive orbits through 2029 and beyond, the asteroid would remain far from Earth, continuing to evolve in a stable pattern for the foreseeable future.
To predict its long-term fate, careful tracking across additional oppositions is necessary. Each new observation reduces orbital uncertainties and clarifies how 199145 formed. It has likely resided in its present orbit for hundreds of millions of years, though it could trace origins back to the early solar system. Non-gravity forces also influence its path, including the Yarkovsky effect—tiny thrust from uneven solar heating that can gradually shift an asteroid’s trajectory over millions of years, altering its course even when only minor forces are acting.
Observing 199145 without a telescope provides little information since its apparent brightness is about 13.8 magnitude, fainter than Pluto at peak. The object is accessible to well-equipped amateur telescopes with apertures of about 20 centimeters or larger, though current observations focus on southern latitudes where viewing conditions are favorable.
[Citation: Astronomical observatories and scholarly studies provide the framework for these assessments, illustrating how orbit determinations and physical property estimates are carried out in practice.]