Two people in space: Asteroids can also have satellites – and this seems to be more common than expected. Using the Gaia space telescope, astronomers have now identified at least 358 asteroids with companions. Some of them are double asteroids consisting of two pieces of almost equal size, others are orbited by a smaller satellite. However, the proportion of these asteroid pairs could be much higher than previous findings suggest, as the team reports in “Astronomy & Astrophysics.”
Astronomers have already identified millions of asteroids in our solar system – and new ones are added almost every day. Most of these pieces orbit the Asteroid belt between Mars and Jupiter, many of them are relics of the early days of the solar system, others are debris from past collisions. Even near the Earth and on orbits crossing the Earth’s orbit There are thousands of pieces, larger and smaller, and there could be many more. in the area near the sun hide in the orbits of Venus and Mercury.
Looking for subtle somersault movements
But most of the asteroids known so far are solitary, Couples However, they are a rather rare phenomenon in observations. Although models suggest that about 15% of all asteroids have a companion, only about 500 do. Double Asteroids or discovered pieces with smaller moons. “Double asteroids are difficult to detect because they are usually quite small and far away from us,” says lead author Luana Liberato of the Côte d’Azur Observatory.
That is why Liberato and his team conducted a targeted search for double asteroids and asteroid moons. To do this, they evaluated information from the third data catalog of the Gaia space telescope. This not only maps the positions and movements of stars, but also provides – almost incidentally – data on more than 150,000 asteroids in the solar system. The astronomers looked for tiny fluctuations in the spectrum, such as those that typically occur during gravitational “taws” between two orbiting objects.
358 pairs in one go
In fact, the astronomers found what they were looking for: Despite particularly strict exclusion criteria and rather conservative statistical analyses, they discovered the telltale wobble that indicates a companion in 358 asteroids. Only six of these objects were previously known to be double asteroids, the team reports. “This shows that there are many more asteroid moons waiting to be discovered,” Liberato says.
The majority of newly discovered double asteroids orbit in the asteroid belt, as orbital analyses have shown. But astronomers have also found pairs in orbits that cross the orbits of Mars or Earth. When it comes to the size of asteroid moons, two particularly common types have emerged: on the one hand, small, rapidly rotating lumps with even smaller moons, and on the other hand, pairs of two asteroids of almost the same size.
Just the beginning
However, the search for asteroid moons is only just beginning, as astronomers also point out. Many of these pairs are difficult to detect with current telescopes and methods: the spectral signature of their joint “dance” around each other is too weak. “But despite these limitations, we have demonstrated the possibilities that Gaia also offers for the discovery of asteroid satellites through astrometry,” emphasize Liberato and his colleagues. “We have thus laid the foundation for more in-depth future searches.” (Astronomy & Astrophysics, 2024; is that i: 10.1051/0004-6361/202349122)
Source European Space Agency (ESA)
August 9, 2024 – Nadja Podbregar