According to OSIRIS-REx Bennu makes one revolution around its axis in 4.3 hours.
Astronomers found that the rotation period of the asteroid Bennu, which is now studying interplanetary station OSIRIS-REx, is reduced by about one second every hundred years. This can lead to its destruction within a few million years, and for the acceleration process, according to scientists, responsible YORP effect. The article was published in the journal Geophysical Research Letters, informs Rus.Media.
The 500-meter near-earth asteroid (101955) Bennu is representative of a carbon asteroid spectral class. The study of such objects can provide important information about the formation and evolution of the Solar system, in addition, it is believed that carbon-rich asteroids such as Bennu, may be responsible for the supply of amino acids and water on the young Earth. Bennu was chosen as a target for interplanetary robotic spacecraft OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer), which is now studying it from orbit. At the beginning of July 2020 the station will be closer to the surface of the asteroid and collect it using a special manipulator 60 grams of dust and fragments of rock, after which, in March 2021, the spacecraft will go to the Earth, and throw into the atmosphere the capsule with the soil in September 2023.
In the new work, a team of astronomers led by Mike Nolan (Mike Nolan) studied how the rotation rate of the asteroid over time. For this purpose, the researchers analyzed data from ground-based observations of Bennu, conducted in 1999 and 2005, and data for 2012, obtained by the space telescope “Hubble” and the new results obtained OSIRIS-REx. It turned out that the rotation period of Bennu is reduced by about one second every hundred years, it can lead to the fact that within a few million years, the rotation rate of the asteroid will grow strong enough in order to begin the process of its destruction. Now, according to OSIRIS-REx and Bennu makes one revolution around its axis in 4.3 hours.
There are several hypotheses explaining the variation of the rotation speed, such as the change of the moment of inertia in a collision with another object or mass loss as a result of various processes. However, the most likely mechanism of acceleration was observed in other near-earth asteroids, beginning with (54509) YORP, is the effect of Yarkovsky – o ‘ Keefe – Radzievskiy – Padaka which consists of changing the speed of rotation of the asteroid asymmetrical shapes under the influence of solar radiation. The correctness of this idea must confirm the OSIRIS-REx on the basis of further observations, during which he will determine the exact shape of the asteroid, the thermal properties of the surface and distribution of gravity near it.
Another current mission to deliver earth from the asteroid – automatic station “Hayabusa-2”. The probe is 27 June 2018 has arrived at her destination, the asteroid 162173 Ryugu, which refers to the most common type of asteroids are class C. studying the chemical properties of matter will allow scientists to judge the composition protozoan nebula.