Astronomers have discovered an inexplicable acceleration of the rotation of the potentially dangerous asteroid Phaeton. It turned out that the period of its own rotation decreases by about 4 milliseconds per year, scientists from the University of Central Florida reported.
The asteroid Phaethon (3200) has a diameter of about 6 kilometers and is one of the largest asteroids that pass near the Earth’s orbit and are potentially hazardous. The period of its revolution around its axis is approximately 3.6 hours.
It was discovered in 1983 thanks to data from the IRAS space observatory. Further observations showed that the asteroid has an unusually quail egged elongated orbit, crossing the orbits of all four terrestrial planets.
For decades, scientists have been observing Phaeton using optical and radio telescopes, which made it possible to build its model and study the characteristics of the orbit. Using Phaethon’s light curves from 1989 to 2021 and data from 2019-2021 occultations of stars by this asteroid, astronomer Sean Marshall of the Arecibo Observatory refined its dimensions, shape, and rotation data.
However, comparing the characteristics of the model, the scientist noticed a clear discrepancy between them and the most recent asteroid light curves obtained since the end of 2021.
This unexpected anomaly – a clear discrepancy between theory and practice – not only introduces uncertainty into forecasts, but also threatens the upcoming DESTINY + mission (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science), planned by the Japanese.
The Japanese Aerospace Exploration Agency (JAXA) intends to send a probe to Phaeton in 2 years to clarify its composition, size, orbit and structure. The landing planned for 2028 may not work and no special clarifications will follow. In short, calculations and models need to be corrected.
According to the data that NASA received from its STEREO-A satellite, in 2009 Phaeton unexpectedly became 2 times brighter. Scientists believe that this phenomenon testified to the released jet – ice covered with dust which could evaporate abruptly. It could also be sodium, whose existence is also suspected.
“The moments when the model was the brightest did not coincide with the moments when the highest brightness of Phaethon was observed in reality,” the astronomer explained. “I realized that this can be explained by a smooth change in the period of Phaethon shortly before the observations of 2021.”
The exact reason for this is not yet clear, but Marshall suggested that it could be due to the comet-like activity of the asteroid during its approach to the Sun in December 2020.
However, after a more thorough analysis of all the data from 1989 to 2021, the scientist realized that the behavior of the asteroid is consistent with the presence of a small constant acceleration of rotation, due to which the rotation period decreases by 4 milliseconds annually.
A similar asteroid ended the age of dinosaurs
Phaeton became only the 11th known asteroid, in which astronomers recorded a change in the frequency of its own rotation.
From current calculations it follows that in the next hundred years the asteroid should not crash into our planet but will get closer to it and on December 14, 2093 Phaeton will be less than 3 million kilometers away. Unless of course the trajectory of its movement by this time does not change and it can.
At one time, astronomers believed that the diameter of Phaethon was 5 kilometers. As a result of observations carried out in 2017, it turned out that it is much larger – 6 kilometers. The last time – about 66 million years ago – the blast from a slightly larger asteroid was supposedly killed the dinosaurs.
Will a small change in the orbit of such a large object potentially lead to a dangerous collision in the future?