Two notable discoveries were made at once in the inner regions of the solar system: an "impossible" ring of dust was found on Mercury, and on Venus - a group of its own asteroids.
The remnants of the gas and dust cloud from which the solar system was formed, small fragments scattered by the collisions of comets and asteroids - all this dust accumulates in some "gravitational corners" around the Sun, forming rarefied rings. Such a dust ring, filled with asteroid debris, is along the Earth's orbit. And in two new articles (1, 2), published in The Astrophysical Journal, scientists report on Mercury's own ring and asteroids orbiting Venus. “It's not every day that you find something new in the inner solar system,” stresses astronomer Marc Kuchner.
Guillermo Stenborg and his colleagues at the US Navy Research Laboratory used data from a pair of twin STEREO satellites observing the Sun. For such studies, it is necessary to accurately take into account the contribution of radiation reflected by the dust particles surrounding the star. Therefore, Stenborg et al. Developed a model describing the movement of dust in the vicinity of the Sun. She showed that a dust ring had accumulated along the orbit of Mercury, with a density about five percent higher than the neighboring regions.
Previously, this was considered not very likely: Mercury is not massive enough and is too close to the Sun to hold its own dust ring. Nevertheless, it is observed throughout the entire orbit. Scientists estimate that the ring is more than 4,800 kilometers wide, far exceeding the diameter of Mercury itself.
The authors of the second publication are Mark Küchner and Petr Pokorný from the Space Flight Center. Goddard NASA - studied the dust ring of Venus. It is much larger than the Mercurian, reaching 25 million kilometers in height and nine million kilometers in width, and exceeding the surrounding area by 10 percent in density. The existence of a dust ring in the orbit of Venus was first shown back in 2007.
A pair of STEREO probes and a dust ring of Venus / © Tom Bridgman, NASA Scientific Visualization Studio
It was assumed that it, like the dust in Earth's orbit, is made up of fragments of continuously colliding bodies from the asteroid belt. However, all attempts by Küchner and Pokorna to simulate this process ended in failure: the Earth's gravity "collected" a stream of dust from the asteroid belt, preventing it from reaching the Venusian orbit. This made scientists think about a different origin of the local dust and simulate other possible scenarios.
As a result, they came to the conclusion that there is a dust source of its own in the orbit of Venus, a group of asteroids orbiting the Sun together with the planet. Most likely, these are large fragments left over from the time of the formation of Venus. Modeling has shown that if there were at least 10 thousand such asteroids in its orbit 4.5 billion years ago, then today there could be about 800 of them. However, telescopes still have to find them to confirm the accuracy of these - so far purely theoretical - results …